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Deposition rates of viruses and bacteria above the atmospheric boundary layer
Abstract
Aerosolization of soil-dust and organic aggregates in sea spray facilitates the long-range transport of bacteria, and likely
viruses across the free atmosphere. Although long-distance transport occurs, there are many uncertainties associated with
their deposition rates. Here, we demonstrate that even in pristine environments, above the atmospheric boundary layer, the
downward flux of viruses ranged from 0.26 × 109 to >7 × 109 m−2 per day. These deposition rates were 9–461 times greater
than the rates for bacteria, which ranged from 0.3 × 107 to >8 × 107 m−2 per day. The highest relative deposition rates for
viruses were associated with atmospheric transport from marine rather than terrestrial sources. Deposition rates of bacteria
were significantly higher during rain events and Saharan dust intrusions, whereas, rainfall did not significantly influence
virus deposition. Virus deposition rates were positively correlated with organic aerosols <0.7 μm, whereas, bacteria were
primarily associated with organic aerosols >0.7 μm, implying that viruses could have longer residence times in the
atmosphere and, consequently, will be dispersed further. These results provide an explanation for enigmatic observations
that viruses with very high genetic identity can be found in very distant and different environments.
... Bacterial diversity decreased from sources to colonizing tanks, suggesting two potential, non-mutually exclusive scenarios: (i) many bacterial taxa that occur in soil or water rarely disperse in the atmosphere or colonize aquatic habitat and (ii) environmental filtering also plays a role by preventing their survival and establishment. The aerial dispersers also showed greatest taxonomic affinity with the soil community ( Fig. 3b and 4b), consistent with previous studies showing the dispersal of airborne bacteria is facilitated by attachment to soil-dust or organic aggregates (12,13,43). While the Salton Sea and surrounding water bodies provide abundant sources of aquatic dispersers, the landscape surrounding our study area is primarily terrestrial (Fig. 1). ...
... We found colony-forming and organic-covered eukaryotes to be effective dispersers. Based on these results, we hypothesize that coloniality and organic cell cover may confer protection against desiccation and effective attachment to dust and/or organic aggregates for air dispersal (43). Moreover, coloniality might be advantageous for cells to travel further due to greater exposure to wind; however, this hypothesis needs further evaluation. ...
... Among motility-associated traits, floater and attached eukaryotes were significantly more abundant among colonizers and air dispersers respectively. Cells with attaching strategies may be able to actively transport through the air attached to dust or organic particles (43). Cell size, covering, and coloniality affect resource acquisition and predator susceptibility in addition to dispersal and colonization (Fig. 6), indicating the potential for tradeoffs among these ecological functions. ...
Many microbes disperse through the air, yet the phenotypic traits that enhance or constrain aerial dispersal or allow successful colonization of new habitats are poorly understood. We used a metabarcoding bacterial and eukaryotic data set to explore the trait structures of the aquatic, terrestrial, and airborne microbial communities near the Salton Sea, California, as well as those colonizing a series of experimental aquatic mesocosms. We assigned taxonomic identities to amplicon sequence variants (ASVs) and matched them to functional trait values through published papers and databases that infer phenotypic and/or metabolic traits information from taxonomy. We asked what traits distinguish successful microbial dispersers and/or colonizers from terrestrial and aquatic source communities. Our study found broad differences in taxonomic and trait composition between dispersers and colonizers compared to the source soil and water communities. Dispersers were characterized by larger cell diameters, colony formation, and fermentation abilities, while colonizers tended to be phototrophs that form mucilage and have siliceous coverings. Shorter population doubling times, spore-, and/or cyst-forming organisms were more abundant among the dispersers and colonizers than the sources. These results show that the capacity for aerial dispersal and colonization varies among microbial functional groups and taxa and is related to traits that affect other functions like resource acquisition, predator avoidance, and reproduction. The ability to disperse and colonize new habitats may therefore distinguish microbial guilds based on tradeoffs among alternate ecological strategies.
IMPORTANCE
Microbes have long been thought to disperse rapidly across biogeographic barriers; however, whether dispersal or colonization vary among taxa or groups or is related to cellular traits remains unknown. We use a novel approach to understand how microorganisms disperse and establish themselves in different environments by looking at their traits (physiology, morphology, life history, and behavior characteristics). By collecting samples from habitats including water, soil, and the air and colonizing experimental tanks, we found dispersal and invasion vary among microorganisms. Some taxa and functional groups are found more often in the air or colonizing aquatic environments, while others that are commonly found in the soil or water rarely disperse or invade new habitat. Interestingly, the traits that help microorganisms survive and thrive also play a role in their ability to disperse and colonize. These findings have significant implications for understanding microorganisms’ success and adaptation to new environments.
... These conditions are reminiscent of the Mars-like environment (DasSarma et al., 2020;Lin et al., 2022;Smith and Sowa, 2017). Although multiple environmental stressors including strong radiation, hypobaric conditions, nutrient scarcity, extreme temperatures and desiccation are complex and significant challenges of near space, microbial cells including archaea, bacteria and fungi are still present in this region (below 50 km) (Reche et al., 2018). In low-altitude atmosphere and near space, microorganisms can be transported up, down or horizontally in the form of bioaerosols and they may still be metabolically active in some extreme atmospheric environments (DasSarma and DasSarma, 2018). ...
... Biomass was observed to decrease at 35-38 km in air samples collected using helium balloons at different altitudes (3-38 km) in the southwestern United States (Bryan et al., 2019). It has been observed that viruses have a greater downward flux and longer residence times than bacteria in the atmosphere, as reported by Reche et al. (2018). As a result, viruses are more likely to be dispersed over larger distances in the atmosphere. ...
... As a result, viruses are more likely to be dispersed over larger distances in the atmosphere. The detection of viable microorganisms in near space highlights the importance of atmospheric biosecurity, particularly for human health, as pathogenic bacteria and viruses that may carry animal pathogens can potentially pose a significant risk (Reche et al., 2018;Wickramasinghe, 2003). Therefore, extensive research is urgently required to extend our understanding of the distribution, environmental function and survival strategies of microorganisms in near space. ...
Earth's near space is an extreme atmosphere environment with high levels of radiation, low atmospheric pressure and dramatic temperature fluctuations. The region is above the flight altitude of aircraft but below the orbit of satellites, which has special and Mars-like conditions for investigating the survival and evolution of life. Technical limitations including flight devices, payloads and technologies/methodologies hinder microbiological research in near space. In this study, we investigated microbial survival and adaptive strategies in near space using a scientific balloon fight mission and multi-omics analyses. Methods for sample preparation, storage, protector and vessel were optimized to prepare the exposed microbial samples. After 3 h 17 min of exposure at a float altitude of ~32 km, only Bacillus strains were alive with survival efficiencies of 0-10-6. Diverse mutants with significantly altered metabolites were generated, firstly proving that Earth's near space could be used as a new powerful microbial breeding platform. Multi-omics analyses of mutants revealed cascade changes at the genome, transcriptome and proteome levels. In response to environmental stresses, two mutants had similar proteome changes caused by different genomic mutations and mRNA expression levels. Metabolic network analysis combined with proteins' expression levels revealed that metabolic fluxes of EMP, PPP and purine synthesis-related pathways were significantly altered to increase/decrease inosine production. Further analysis showed that proteins related to translation, molecular chaperones, cell wall/membrane, sporulation, DNA replication/repair and anti-oxidation were significantly upregulated, enabling cells to efficiently repair DNA/protein damages and improve viability against environmental stress. Overall, these results revealed genetic and metabolic responses of Bacillus to the harsh conditions in near space, providing a research basis for bacterial adaptive mechanisms in extreme environments.
... Atmospheric deposition with Saharan dust is reported to introduce organic matter and nutrients such as nitrogen (N), phosphorus (P), calcium (Ca), and iron (Fe) to Sierra Nevada high-mountain lakes which subsequently impact lake primary and bacterial productivity [2,13]. In addition, it has been reported that bacteria from the Sahara Desert are deposited to high-mountain lakes in Sierra Nevada through dust depositions at a rate from 3 × 10 6 to > 80 × 10 6 cells m −2 per day, particularly during rainy events [14]. Saharan dust was shown to have a significant positive effect on bacterial abundance but not on the richness, diversity, or composition of indigenous bacterial communities in ex situ microcosm experiments using water from a reservoir at a low altitude in Sierra Nevada [15]. ...
... The significant contribution of different physicochemical properties to variations in the alpha and beta diversity of prokaryotic communities highlights the ability of the sediment microbiome of highmountain lakes of Sierra Nevada to respond to external inputs of different nutrients via Saharan dust intrusion events ( Table 2). This is in line with results in previous studies showing that Saharan dust can impact the abundance of bacterial communities using ex situ microcosm experiments in reservoirs [14] and in situ experiments in a high-mountain lake of Sierra Nevada (La Caldera Lake; Vila et al. submitted). The negative influence of NO 3 − and PO 4 3− concentrations and values of the TC/TN and TOC/TN ratios on alpha diversity agree with previous studies that reported decreases in the diversity of prokaryotic communities in freshwater and marine ecosystems affected by these inorganic and organic nutrients [20,45]. ...
Mediterranean high-mountain lakes are being increasingly affected by strong Saharan dust deposition events. However, the ecological impacts of these severe atmospheric episodes remain largely unknown. We examined the effects of a strong Saharan dust intrusion to the Iberian Peninsula in 2022 on the physicochemical parameters and prokaryotic communities in sediments of nine high-mountain lakes of Sierra Nevada (Spain) located above 2800 m.a.s.l and in different orientations (north vs. south). A previous year (2021), with lower Saharan dust deposition with respect to 2022, was used for interannual comparisons. The strong dust deposition to the high-mountain lakes resulted in a significant increase in sediment nutrient availability which was linked to changes in the composition of prokaryotic communities. Decreases in alpha diversity and changes in beta diversity of prokaryotic communities were mainly observed in lakes located in the south compared to the north orientation likely because the former was more affected by the atmospheric dust deposition episode. Dust intrusion to the high-mountain lakes resulted in significant changes in the relative abundance of specific genera involved in important nutrient cycling processes such as phosphate solubilization, nitrogen fixation, nitrification, and denitrification. Saharan dust deposition also increased predicted microbial functionality in all lakes. Our findings show that severe atmospheric dust inputs to remote high-mountain lakes of Sierra Nevada can have significant biogeochemical and biodiversity consequences through changes in nutrient availability and prokaryotic communities in sediments of these freshwater ecosystems. This information contributes to understanding how Mediterranean high-mountain lakes of Sierra Nevada face strong intrusions of Saharan dust and their ecological consequences.
Supplementary Information
The online version contains supplementary material available at 10.1007/s00248-024-02416-w.
... The study confirms the usefulness of HYSPLIT models as a tool when determining 31 seasonal effects, distances, and inform near real-time risk of windborne PRRSv transmission that 32 can be useful in future outbreak investigations and implementing timely control measures. 33 Keywords: pig diseases; spatial epidemiology; Lagrangian models; aerial dispersion; HYSPLIT; 34 airborne; epidemiology of PRRSv 35 1. Background 36 Porcine reproductive and respiratory syndrome virus (PRRSv) is recognized as the 37 costliest endemic swine pathogen affecting the U.S. with an estimated cost of more than 38 $664 million per year due to production losses, treatment costs, and excessive mortality 39 [1,2]. Transmission of PRRSV between farms is primarily from animal movement [3], 40 contact with infected gilts and sows [4,5], and airborne/windborne transmission of 41 aerosolized particles [6,7]. ...
... All other settings such as horizontal and vertical mixing coefficients were used at 162 the default settings of HYSPLIT. Further details on Lagrangian models [33], dry 163 deposition of airborne viruses [34], and details on the dry and wet deposition of 164 atmospheric gases and modeling dry and wet deposition on HYSPLIT are found 165 elsewhere [18,22]. The limitations of HYSPLIT and similar ADMs are discussed elsewhere 166 [15][16]. ...
Modeling windborne transmission of aerosolized pathogens is challenging. We adapted an at-mospheric dispersion model named Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) to simulate windborne dispersion of porcine reproductive and respiratory syndrome virus (PRRSv) between swine farms and incorporated the findings into an outbreak investigation. The risk was estimated semi-quantitatively based on the cumulative daily deposi-tion of windborne particles, and the distance to closest emitting farm with an ongoing outbreak. Five years of data (2014 : 2018) were used to study seasonal differences of deposition thresholds of the airborne particles containing PRRSv and to evaluate model in relation to risk prediction and barn air filtration. When considered the 14-day cumulative deposition, in Winter, above threshold particle depositions would reach up to 30 km from emitting farms with 84% of them being within 10km. Long-distance pathogen transmission was highest in Winter and Fall, lower in Spring, and least in Summer. The model successfully replicated the observed seasonality of PRRSv where Fall and Winter posing a higher risk for outbreaks. Reaching the humidity and temperature thresholds tolerated by the virus in Spring and Summer reduced the survival and infectivity of aerosols beyond 10 -20 km. Within in the data limitations of voluntary participa-tion, when assumed wind as the sole route of PRRSv transmission, the predictive performance of the model was fair with >0.64 AUC. Barn air filtration was associated with fewer outbreaks, particularly when exposed to high levels of viral particles. The study confirms the usefulness of HYSPLIT models as a tool when determining seasonal effects, distances, and inform near re-al-time risk of windborne PRRSv transmission that can be useful in future outbreak investigations and implementing timely control measures.
... Indeed, viral lysis of phytoplankton results in the accumulation of viral particles and a mixture of high molecular weight organic material originating from bursting cells 22 , including transparent exopolymer particles (TEP) 23,24 . Phytoplankton viruses have been observed in primary marine aerosols by microscopy 15 and DNA sequencing 16 , as well as within dust and above the atmospheric boundary layer via flow cytometry 25,26 . Virus infection of phytoplankton alters DOM compared to healthy cells 27,28 , but the effect of viral infection, including the complex suite of DOM from lysed cells compared to healthy cells and individual virus particles, on CCN activity remains unclear. ...
... Resident phytoplankton were also shown to have high markers of cellular reactive oxygen stress (reactive oxygen species, oxidized lipids), which supports previous studies documenting a physiological link between oxidative stress and TEP production 45 . Phytoplankton accumulation and viral-mediated demise follow predictable seasonal patterns detectable by ocean remote sensing [46][47][48] , highlighting the potential for incorporating viral infection in marine aerosol cloud models if it resulted in primary aerosols with altered CCN activity 26 . ...
Viral infection of phytoplankton is a pervasive mechanism of cell death and bloom termination, which leads to the production of dissolved and colloidal organic matter that can be aerosolized into the atmosphere. Earth-observing satellites can track the growth and death of phytoplankton blooms on weekly time scales but the impact of viral infection on the cloud forming potential of associated aerosols is largely unknown. Here, we determine the influence of viral-derived organic matter, purified viruses, and marine hydrogels on the cloud condensation nuclei activity of their aerosolized solutions, compared to organic exudates from healthy phytoplankton. Dissolved organic material derived from exponentially growing and infected cells of well-characterized eukaryotic phytoplankton host-virus systems, including viruses from diatoms, coccolithophores and chlorophytes, was concentrated, desalted, and nebulized to form aerosol particles composed of primarily of organic matter. Aerosols from infected phytoplankton cultures resulted in an increase in critical activation diameter and average molar mass in three out of five combinations evaluated, along with a decrease in organic kappa (hygroscopicity) compared to healthy cultures and seawater controls. The infected samples also displayed evidence of increased surface tension depression at realistic cloud water vapor supersaturations. Amending the samples with xanthan gum to simulate marine hydrogels increased variability in organic kappa and surface tension in aerosols with high organic to salt ratios. Our findings suggest that the pulses of increased dissolved organic matter associated with viral infection in surface waters may increase the molar mass of dissolved organic compounds relative to surface waters occupied by healthy phytoplankton or low phytoplankton biomass.
... Indeed, there is an induced magnetosphere around Mars as Mars is conductive and there are electrodynamic interactions with a magnetized flowing plasma, such as the solar wind. This implies the existence of induced currents (Ramstad et al., 2020). Five years of magnetic field measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter have been used by these authors to map these currents. ...
Mars is the fourth planet from the Sun. Today it is cold, dry, and covered by a reddish bedrock and regolith. The surface is little protected from radiation due to a thin atmosphere and the lack of a substantial magnetic field. It is however thought to have been very different: that in its early history, about 4 Gyr ago, it had a thicker atmosphere and a magnetic field. Water seems to have flown, at least periodically, on the surface. It might even have harboured life. In this chapter, the major developments in Mars’s geological history, as well as its current environmental conditions, are laid out. They are then discussed in the context of space exploration. Our analysis suggests that resources for human explorers may be sourced on site, notably water, building materials, and nutrients for growing food. It also highlights the many hazards which would be faced on Mars, including radiation, a toxic and oxidizing soil, little organic material, and a harsh climate.
... A variety of airborne microbial pathogens and allergens have been found in swine farms, including Salmonella, Staphylococcus, Fusobacterium inducens, Bacillus cereus, and Staphylococcus aureus [14,15]. In addition, aerosols in swine farms that carry pathogenic microorganisms can be transported over great distances [16,17]. For example, Dee et al. [18] detected porcine Mycoplasma pneumoniae DNA in air samples collected 4.7 km from a swine farm. ...
Particulate matter (PM2.5) in pig houses and the microorganisms in PM2.5 restrict the sustainable development of the pig industry and have a negative influence on environmental sustainability. This study aimed to investigate the morphological characteristics and diel microbial composition of PM2.5 in fattening pig sheds and explore how changes in the diel microbial composition of PM2.5 correlate with environmental factors and sources. To this end, environmental data from a fattening pig house were monitored, and PM2.5, feed, and faecal particles were examined using electron microscopy. Additionally, the bacterial and fungal assemblages contained in PM2.5 were analysed using 16S and 18S rRNA gene sequencing, respectively. The results showed that NH3, CO2, temperature, and relative humidity were significantly higher at night than during the day. PM2.5 particles from the fattening pig house exhibited different morphologies such as spherical, flocculent, and chain structures. The microbial diversity and bacterial assemblage showed significant variations, which were related to diel environmental factors in the fattening house. In addition, faeces may be the main source of airborne bacteria and feed may be the main source of airborne fungi in fattening houses. These findings provide a scientific basis for exploring the potential risks of the morphological characteristics of PM2.5 and its microbial composition to human and animal health. Additionally, they contribute to the sustainable development of the pig industry and the protection of the environment.
... Viruses are the most abundant microbes on the planet [7][8][9] and RNA viruses dominate the eukaryotic virome [10,11]. Hundreds of viruses have been identified in recent years in arthropods [10][11][12][13][14][15], illustrating that invertebrates usually have a greater and more diverse virome than vertebrates [16]. ...
The maize leafhopper (Dalbulus maidis) is a significant threat to maize crops in tropical and subtropical regions, causing extensive economic losses. While its ecological interactions and control strategies are well studied, its associated viral diversity remains largely unexplored. Here, we employ high-throughput sequencing data mining to comprehensively characterize the D. maidis RNA virome, revealing novel and diverse RNA viruses. We characterized six new viral members belonging to distinct families, with evolutionary cues of beny-like viruses (Benyviridae), bunya-like viruses (Bunyaviridae) iflaviruses (Iflaviridae), orthomyxo-like viruses (Orthomyxoviridae), and rhabdoviruses (Rhabdoviridae). Phylogenetic analysis of the iflaviruses places them within the genus Iflavirus in affinity with other leafhopper-associated iflaviruses. The five-segmented and highly divergent orthomyxo-like virus showed a relationship with other insect associated orthomyxo-like viruses. The rhabdo virus is related to a leafhopper-associated rhabdo-like virus. Furthermore, the beny-like virus belonged to a cluster of insect-associated beny-like viruses, while the bi-segmented bunya-like virus was related with other bi-segmented insect-associated bunya-like viruses. These results highlight the existence of a complex virome linked to D. maidis and paves the way for future studies investigating the ecological roles, evolutionary dynamics, and potential biocontrol applications of these viruses on the D. maidis—maize pathosystem.
... Bacteriophages, also known as phages, are viruses that infect bacteria, and they are found in almost all environments, including soil, fresh, and marine water samples, and most recently, in the free atmosphere [12,13]. Bacteriophages can have one of four different life cycles ( Figure 1): lytic, lysogenic, chronic, and pseudolysogenic cycles. ...
To explore how microbial interactions within the rhizosphere influence the diversity and functional roles of bacterial communities, we isolated 21 bacterial strains from soil samples collected near Rocky Branch Creek on the University of South Carolina campus. Our findings revealed that a significant proportion of the isolated bacterial strains are lysogenic. Contrary to predictions of a narrow host range, most of the bacteriophages derived from these lysogenic bacteria demonstrated the ability to infect a broad range of bacterial strains. These results suggest that the bacterial community shares a complex phage community, creating an intricate web of interactions. This study enhances our understanding of the relationships between phages and their bacterial hosts in soil ecosystems, with implications for ecological balance and agricultural practices aimed at improving plant health through microbial management strategies.
... Limited data exist to date on the magnitude of microorganism propagation in the free troposphere ( 10 ), above the planetary boundary layer (PBL), whether attached to soil dust ( 11 ) or to organic aggregates ( 12 ). For a review, see ref. 13 . ...
The existence of viable human pathogens in bioaerosols which can cause infection or affect human health has been the subject of little research. In this study, data provided by 10 tropospheric aircraft surveys over Japan in 2014 confirm the existence of a vast diversity of microbial species up to 3,000 m height, which can be dispersed above the planetary boundary layer over distances of up to 2,000 km, thanks to strong winds from an area covered with massive cereal croplands in Northeast (NE) Asia. Microbes attached to aerosols reveal the presence of diverse bacterial and fungal taxa, including potential human pathogens, originating from sewage, pesticides, or fertilizers. Over 266 different fungal and 305 bacterial genera appeared in the 10 aircraft transects. Actinobacteria, Bacillota, Proteobacteria, and Bacteroidetes phyla dominated the bacteria composition and, for fungi, Ascomycota prevailed over Basidiomycota. Among the pathogenic species identified, human pathogens include bacteria such as Escherichia coli, Serratia marcescens, Prevotella melaninogenica, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus saprophyticus, Cutibacterium acnes, Clostridium difficile, Clostridium botulinum, Stenotrophomonas maltophilia, Shigella sonnei, Haemophillus parainfluenzae and Acinetobacter baumannii and health-relevant fungi such as Malassezia restricta , Malassezia globosa , Candida parapsilosis and Candida zeylanoides, Sarocladium kiliense, Cladosporium halotolerans, and Cladosporium herbarum . Diversity estimates were similar at heights and surface when entrainment of air from high altitudes occurred. Natural antimicrobial-resistant bacteria (ARB) cultured from air samples were found indicating long-distance spread of ARB and microbial viability. This would represent a novel way to disperse both viable human pathogens and resistance genes among distant geographical regions.
... Viruses are the most abundant microbes on the planet [7][8][9] and RNA viruses dominate the eukaryotic virome [10,11]. Hundreds of viruses have been identified in recent years in arthropods [10][11][12][13][14][15], illustrating that invertebrates usually have a greater and more diverse virome than vertebrates [16]. ...
The maize leafhopper ( Dalbulus maidis ) is a significant threat to maize crops in tropical and subtropical regions, causing extensive economic losses. While its ecological interactions and control strategies are well-studied, its associated viral diversity remains largely unexplored. Here, we employ high-throughput sequencing data mining to comprehensively characterize the D. maidis RNA virome, revealing novel and diverse RNA viruses. We characterized six new viral members belonging to distinct families, with evolutionary cues of beny-like viruses ( Benyviridae ), bunya-like viruses ( Bunyaviridae ) iflaviruses ( Iflaviridae ), orthomyxo-like viruses ( Orthomyxoviridae ), and rhabdoviruses ( Rhabdoviridae ). Phylogenetic analysis of the iflaviruses places them within the genus Iflavirus in affinity with other leafhoppers-associated iflaviruses. The five-segmented and highly divergent orthomyxo-like virus showed a relationship with other insect associated orthomyxo-like viruses. The rhabdo virus is related with a leafhopper associated rhabdo-like virus. Furthermore, the beny-like virus belonged to a cluster of insect-associated beny-like viruses, while the bi-segmented bunya-like virus was related with other bi-segmented insect-associated bunya-like viruses. These results highlight the existence of a complex virome linked to D. maidis and paves the way for future studies investigating the ecological roles, evolutionary dynamics, and potential biocontrol applications of these viruses on the D. maidis -maize pathosystem.
... Clouds -AR genes have been detected in clouds at concentrations ranging between 1 × 10 3 and 1.6 × 10 4 copies per m 3 of air [278]. This, along with bacterial deposition rates from the atmosphere to the soil of 3 × 10 6 to >8 × 10 7 per m 2 per day [279], indicates a relevant route of dispersion of AR bacteria and genes. ...
The understanding of antibiotic resistance, one of the major health threats of our time, is mostly based on dated and incomplete notions, especially in clinical contexts. The “canonical” mechanisms of action and pharmacodynamics of antibiotics, as well as the methods used to assess their activity upon bacteria, have not changed in decades; the same applies to the definition, acquisition, selective pressures, and drivers of resistance. As a consequence, the strategies to improve antibiotic usage and overcome resistance have ultimately failed. This review gathers most of the “non-canonical” notions on antibiotics and resistance: from the alternative mechanisms of action of antibiotics and the limitations of susceptibility testing to the wide variety of selective pressures, lateral gene transfer mechanisms, ubiquity, and societal factors maintaining resistance. Only by having a “big picture” view of the problem can adequate strategies to harness resistance be devised. These strategies must be global, addressing the many aspects that drive the increasing prevalence of resistant bacteria aside from the clinical use of antibiotics.
... (2) The frequency (p) and rate (j 0 ) of aerosolization or deposition events are assumed to be equal among species. This could be generalized to allow for the empirically observed species-specific parameters [55][56][57][58][59]. ...
Airborne dispersal of microorganisms is a ubiquitous migration mechanism, allowing otherwise independent microbial habitats to interact via biomass exchange. Here, we study the ecological implications of such advective transport using a simple spatial model for bacteria–phage interactions: the population dynamics at each habitat are described by classical Lotka–Volterra equations; however, species populations are taken as integer, that is, a discrete, positive extinction threshold exists. Spatially, species can spread from habitat to habitat by stochastic airborne dispersal. In any given habitat, the spatial biomass exchange causes incessant population density oscillations, which, as a consequence, occasionally drive species to extinction. The balance between local extinction events and dispersal-induced migration allows species to persist globally, even though diversity would be depleted by competitive exclusion, locally. The disruptive effect of biomass dispersal thus acts to increase microbial diversity, allowing system-scale coexistence of multiple species that would not coexist locally.
... Bacteriophages are viruses that infect bacteria, and they are considered potential biological control agents for bacteria due to their generally narrow host cell specificity. Importantly, bacteriophages, also known as phages, are found in almost all environments including soil, fresh and marine water samples, and most recently in the free atmosphere [1]. They are exceptionally numerous and are approximately ten times more abundant than their bacterial hosts [2]. ...
Previous studies have identified diverse bacteriophages that infect Caulobacter vibrioides strain CB15 ranging from small RNA phages to four genera of jumbo phages. In this study, we focus on 20 bacteriophages whose genomes range from 40 to 60 kb in length. Genome comparisons indicated that these diverse phages represent six Caulobacter phage genera and one additional genus that includes both Caulobacter and Brevundimonas phages. Within species, comparisons revealed that both single base changes and inserted or deleted genetic material cause the genomes of closely related phages to diverge. Among genera, the basic gene order and the orientation of key genes were retained with most of the observed variation occurring at ends of the genomes. We hypothesize that the nucleotide sequences of the ends of these phage genomes are less important than the need to maintain the size of the genome and the stability of the corresponding mRNAs.
... Some laboratory experiments performed by Van Doremalen and coauthors [44] indicated that airborne and fomite transmission of SARS-Cov-2 is plausible since the virus can remain viable and infectious in aerosol for several hours. In addition, another study has already identified the presence of viruses in marine aerosols and dust from the Sahara [45]. Besides, breathing can take PM deep into the lungs so that PMbound viral particles can directly invade the lower respiratory tract, as demonstrated by Sedlmaier and coauthors [46]. ...
... So far, research on viruses included in wet precipitation was mainly focused on viruses relevant to human health, such as enteric or adenoviruses [52][53][54] . Reche, et al. 55 reported that 10 7 bacteria and 10 9 viruses deposit from the atmosphere per m 2 per day, with marine sources having stronger contributions than terrestrial ones. This rate can be one order of magnitude higher for bacteria 56 and perhaps also for viruses. ...
Marine viruses in seawater have frequently been studied, yet their dispersal from neuston ecosystems at the air-sea interface towards the atmosphere remains a knowledge gap. Here, we show that 6.2% of the studied virus population were shared between air-sea interface ecosystems and rainwater. Virus enrichment in the 1-mm thin surface microlayer and sea foams happened selectively, and variant analysis proved virus transfer to aerosols collected at ~2 m height above sea level and rain. Viruses detected in rain and these aerosols showed a significantly higher percent G/C base content compared to marine viruses. CRISPR spacer matches of marine prokaryotes to foreign viruses from rainwater prove regular virus-host encounters at the air-sea interface. Our findings on aerosolization, adaptations, and dispersal support transmission of viruses along the natural water cycle.
... Similar mechanism is responsible for electric charge mediated scavenge and aerosolization of negatively charged bacteria cells [21][22][23], diatoms [11] and enveloped viruses [24,25]. The same electric mechanism of charge mediated adhesion and then transmission of RNA via the positively charged spikes, which are exposed by coronaviruses, to negatively charged membranes of host's biological cells, was reported by Pawłowski [26]. ...
Photographic investigations of rising bubbles in seawater revealed that each bubble may conduct a single or bi-spiraling motion, which resemble architecture of RNA or DNA respectively. The rotational motion results from acceleration of ionic hydrates, which are separated to anionic and cationic domains at the upper and bottom curvatures of the bubble. Afterwards, rotational motion undergoes further acceleration in the bubble upper vortex, followed by deceleration at the vortex tip. During that phase, the spiraling motion cause significant friction that result in polarization of electronegative atoms of H, C, N, O and P. These may be simultaneously arranged around a whirling cationic strands and form phosphate groups, ribose and nitrogen bases equipped with H2 and H3 rotors. It is hypothesized that such hydrogen rotors may operate as generators of electrons, which may be detached from valence shells of electropositive atoms. Then, electrons may flow via nitrogen bases and deoxyribose or ribose to phosphate groups. Next, the negatively charged edges of phosphate groups may attract cationic hydrates and energize their rotational motion in the grooves, then causing also its spiraling projection outward. That may be responsible for replication of nucleotides and its arrangement along the cationic flow into RNA or DNA polymers, in the same manner as originally produced by rising bubbles. Moreover, it points that hydrogen rotors may generate energy needed for viability as well as interact with all physical and chemical fields. Keywords: bubbles in seawater; polarization of electronegative atoms; formation of hydrogen rotors; generation of electrons; electrical features of nucleotides; rotational-electric principles of replication 386 AIMS Biophysics Volume 10, Issue 3, 385-400.
... All other settings, such as horizontal and vertical mixing coefficients, were used at the default settings of HYSPLIT. Further details on Lagrangian models [28], dry deposition of airborne viruses [29], and the dry and wet deposition of atmospheric gases and modeling dry and wet deposition on HYSPLIT are found elsewhere [14,18]. The limitations of HYSPLIT and similar ADMs are discussed elsewhere [30,31]. ...
Modeling the windborne transmission of aerosolized pathogens is challenging. We adapted an atmospheric dispersion model named the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to simulate the windborne dispersion of porcine reproductive and respiratory syndrome virus (PRRSv) between swine farms and incorporated the findings into an outbreak investigation. The risk was estimated semi-quantitatively based on the cumulative daily deposition of windborne particles and the distance to the closest emitting farm with an ongoing outbreak. Five years of data (2014:2018) were used to study the seasonal differences of the deposition thresholds of the airborne particles containing PRRSv and to evaluate the model in relation to risk prediction and barn air filtration. When the 14-day cumulative deposition was considered, in winter, above-threshold particle depositions would reach up to 30 km from emitting farms with 84% of them being within 10 km. Long-distance pathogen transmission was highest in winter and fall, lower in spring, and least in summer. The model successfully replicated the observed seasonality of PRRSv, where fall and winter posed a higher risk for outbreaks. Reaching the humidity and temperature thresholds tolerated by the virus in spring and summer reduced the survival and infectivity of aerosols beyond 10–20 km. Within the data limitations of voluntary participation, when wind was assumed to be the sole route of PRRSv transmission, the predictive performance of the model was fair with >0.64 AUC. Barn air filtration was associated with fewer outbreaks, particularly when exposed to high levels of viral particles. This study confirms the usefulness of the HYSPLIT model as a tool when determining seasonal effects and distances and informs the near real-time risk of windborne PRRSv transmission that can be useful in future outbreak investigations and for implementing timely control measures.
... To identify the back-trajectories followed by the microplastics, the HYSPLIT4 model was then applied, using in input the meteorological data provided by the National Oceanic and Atmospheric Administration. For the configuration of the model, the authors refer to the works of Su et al. (2015), Ashrafi et al. (2014), and Reche et al. (2018), thus we assume that the meteorological fields might have had a grid resolution of 1 • × 1 • or 0.5 • × 0.5 • . The receptor was located at the sampling site, 43 • N 1 • E and 100 m a.g.l. ...
... The results of this study underestimated the propagation range and consistent time of dental airborne contamination because only bacterial contamination was determined [36]. For example, viruses are much smaller and they could have longer residence times in the atmosphere and, consequently, will be dispersed further [37,38]. And the oral biofilm which is more complex was not considered in this study [39]. ...
Background
Using a rotary instrument or ultrasonic instrument for tooth preparation is a basic operation in the dental clinic that can produce a significant number of droplets and aerosols. The dental droplet and aerosol can lead to the transfer of harmful germs. The goal of this study was to analyze the properties of microbiological aerosol created by droplets and aerosol generated by three common tooth-preparation instruments.
Methods
Streptococcus mutans UA159 was used as the biological tracer to visualize the droplets and aerosols. The passive sampling method was used to map the three-dimensional spatial distribution and the six-stage Andersen microbial sampler (AMS) was used as the active sampling method to catch aerosol particles at a specific time.
Results
The aerosol concentration is related to instruments, three-dimensional spatial distribution, and dissipation time. Most aerosols were generated by air turbines. More microorganisms are concentrated at the 1.5 m plane. The majority of the post dental procedure contamination was detected within the 0–10-min period and it decreased rapidly within 30 min.
Conclusion
This study is conducive to the proposal and improvement of relevant infection control measures in dental procedures and provides a basis for the assessment of measures, reducing the risk of nosocomial infection.
... Deposition fluxes are much more accessible than those of emission, as deposits can be easily collected and analyzed and directly expressed as per surface area and time. For bacteria, wet deposition is associated with highest fluxes, reaching up to ~10 7 -10 8 cells/m 2 /h (Reche et al., 2018;Woo and Yamamoto, 2020;Péguilhan et al., 2021). The microbial mixture permanently deposited from air on surfaces brings invaders and competitors to surface environments (Hervas and Casamayor, 2009;Morris and Sands, 2017;Noirmain et al., 2022). ...
The atmosphere is an integral component of the Earth’s microbiome. Abundance, viability, and diversity of microorganisms circulating in the air are determined by various factors including environmental physical variables and intrinsic and biological properties of microbes, all ranging over large scales. The aeromicrobiome is thus poorly understood and difficult to predict due to the high heterogeneity of the airborne microorganisms and their properties, spatially and temporally. The atmosphere acts as a highly selective dispersion means on large scales for microbial cells, exposing them to a multitude of physical and chemical atmospheric processes. We provide here a brief critical review of the current knowledge and propose future research directions aiming at improving our comprehension of the atmosphere as a biome.
... Virome "dysbiosis" therefore appears to be a key characteristic of asthma pathophysiology, potentially amenable to intervention [29][30][31] . Exposure to viruses-and subsequent interactions with the host-are constant in the respiratory tract 32 . Furthermore, at least some viruses may persist 33 . ...
Asthma development and exacerbation is linked to respiratory virus infections. There is limited information regarding the presence of viruses during non-exacerbation/infection periods. We investigated the nasopharyngeal/nasal virome during a period of asymptomatic state, in a subset of 21 healthy and 35 asthmatic preschool children from the Predicta cohort. Using metagenomics, we described the virome ecology and the cross-species interactions within the microbiome. The virome was dominated by eukaryotic viruses, while prokaryotic viruses (bacteriophages) were independently observed with low abundance. Rhinovirus B species consistently dominated the virome in asthma. Anelloviridae were the most abundant and rich family in both health and asthma. However, their richness and alpha diversity were increased in asthma, along with the co-occurrence of different Anellovirus genera. Bacteriophages were richer and more diverse in healthy individuals. Unsupervised clustering identified three virome profiles that were correlated to asthma severity and control and were independent of treatment, suggesting a link between the respiratory virome and asthma. Finally, we observed different cross-species ecological associations in the healthy versus the asthmatic virus-bacterial interactome, and an expanded interactome of eukaryotic viruses in asthma. Upper respiratory virome “dysbiosis” appears to be a novel feature of pre-school asthma during asymptomatic/non-infectious states and merits further investigation.
... They are also ubiquitous. The atmosphere is rich with microbes and transports and deposits many of them throughout Earth's surface in unbelievable numbers: hundreds of millions of viruses and tens of millions of bacteria per square meter per day (Reche et al., 2018). In marine ecosystems, microbes, mostly bacteria, account for approximately 70% of marine biomass and are critical in marine nutrient cycling. ...
... Extreme meteorological events such as volcanic eruptions, dust storms, and wildland fires can aerosolize a large number of viable microbes up to tens of kilometres high in the atmosphere that can be transported short or long distances before landing back on the Earth's surface [1][2][3][4]. Bioaerosols that reach the free troposphere are typically subject to long-range dispersal up to thousands of kilometres [5], whereas those that remain in the lower and most vertically mixed part of the troposphere called the planetary boundary layer account for most local dispersal [6]. During their dispersal through the atmosphere, cells experience stressful conditions including solar radiation, oxidative stress, osmotic shock, and freeze-thaw cycles [7]. ...
Surface microbes are aerosolized into the atmosphere by wind and events such as dust storms and volcanic eruptions. Before they reach their deposition site, they experience stressful atmospheric conditions which preclude the successful dispersal of a large fraction of cells. In this study, our objectives were to assess and compare the atmospheric and lithospheric bacterial cultivable diversity of two geographically different Icelandic volcanic sites: the island Surtsey and the Fimmvörðuháls mountain, to predict the origin of the culturable microbes from these sites, and to select airborne candidates for further investigation. Using a combination of MALDI Biotyper analysis and partial 16S rRNA gene sequencing, a total of 1162 strains were identified, belonging to 72 species affiliated to 40 genera with potentially 26 new species. The most prevalent phyla identified were Proteobacteria and Actinobacteria. Statistical analysis showed significant differences between atmospheric and lithospheric microbial communities, with distinct communities in Surtsey’s air. By combining the air mass back trajectories and the analysis of the closest representative species of our isolates, we concluded that 85% of our isolates came from the surrounding environments and only 15% from long distances. The taxonomic proportions of the isolates were reflected by the site’s nature and location.
... Transit through the atmosphere is strongly related to survivability and the biocidal effects of high ultraviolet light, low temperature and low relative humidity have been identified (Brotto et al., 2015;Hara and Zhang, 2012;Prussin et al., 2017;Šantl-Temkiv et al., 2017;Tong and Lighthart, 2000). However, evidence also suggests that not all microorganisms become airborne in a uniform manner (Aalismail et al., 2019;Michaud et al., 2018), and some taxa may be adapted to enhanced deposition during transit (Reche et al., 2018). Our differential abundance analysis added statistical evidence in support of the taxa enriched in the ABL, and patterns also reflected potential differential adaptation to aerosolization and/or survival as well as source influences (Fig. 4c). ...
The dispersion of microorganisms through the atmosphere is a continual and essential process that underpins biogeography and ecosystem development and function. Despite the ubiquity of atmospheric microorganisms globally, specific knowledge of the determinants of atmospheric microbial diversity at any given location remains unresolved. Here we describe bacterial diversity in the atmospheric boundary layer and underlying soil at twelve globally distributed locations encompassing all major biomes, and characterise the contribution of local and distant soils to the observed atmospheric community. Across biomes the diversity of bacteria in the atmosphere was negatively correlated with mean annual precipitation but positively correlated to mean annual temperature. We identified distinct non-randomly assembled atmosphere and soil communities from each location, and some broad trends persisted across biomes including the enrichment of desiccation and UV tolerant taxa in the atmospheric community. Source tracking revealed that local soils were more influential than distant soil sources in determining observed diversity in the atmosphere, with more emissive semi-arid and arid biomes contributing most to signatures from distant soil. Our findings highlight complexities in the atmospheric microbiota that are relevant to understanding regional and global ecosystem connectivity.
... If the movement is a turbulent flow (e.g., microenvironments mixed), it can instead result in a faster virion movement relative to bacteria [33]. Lastly, virions also may be transported over longer distances, such as through the air, associated with dust, splashed water, or animals, serving as mechanical vectors [34][35][36]. However, it is important to note that this bulk movement is not necessarily relative to the positions of co-located bacteria. ...
Bacteriophages are ubiquitous organisms that can be specific to one or multiple strains of hosts, in addition to being the most abundant entities on the planet. It is estimated that they exceed ten times the total number of bacteria. They are classified as temperate, which means that phages can integrate their genome into the host genome, originating a prophage that replicates with the host cell and may confer immunity against infection by the same type of phage; and lytics, those with greater biotechnological interest and are viruses that lyse the host cell at the end of its reproductive cycle. When lysogenic, they are capable of disseminating bacterial antibiotic resistance genes through horizontal gene transfer. When professionally lytic—that is, obligately lytic and not recently descended from a temperate ancestor—they become allies in bacterial control in ecological imbalance scenarios; these viruses have a biofilm-reducing capacity. Phage therapy has also been advocated by the scientific community, given the uniqueness of issues related to the control of microorganisms and biofilm production when compared to other commonly used techniques. The advantages of using bacteriophages appear as a viable and promising alternative. This review will provide updates on the landscape of phage applications for the biocontrol of pathogens in industrial settings and healthcare.
... Moreover, , has already confirmed the association between higher COVID-19 mortality rates and increased PM concentrations at the Harvard School of Public Health. This is consistent with the findings of previous studies on other viruses (Qin et al., 2020;Reche et al., 2018;Zhao et al., 2019). Lourenco et al. (Amato-Lourenço et al., 2022) detected the SARS-CoV-2 nucleocapsid in six samples and many more SARS-CoV-2 envelopes in 22 out of 38 total suspended particle samples (Table 4). ...
Road dust pollution is a complex atmospheric issue that poses a significant ecotoxicological threat to human health and the environment. The presence of viruses in road dust can put humans at risk of infection, as airborne viral particles are a potential synergist to respiratory infirmities, leading to widespread mortality and morbidity. This corroborates the increasing number of desk-based studies on the effects of road dust. However, the role of road dust in the spread and pathogenicity of viruses has scarcely been explored, and there is still no certainty regarding whether road dust participates in viral transmission or causes infectious diseases. Therefore, the current knowledge and mechanisms of road-dust-associated viruses and other pathogenic microorganisms are critically reviewed, highlighting the importance of keeping an eye out for road-dust-associated viruses, as they represent hotspots for viral transmission. In this overview, we evaluate the emissions, associated contaminants, and public health implications of exposure to road-dust-associated viruses. A summary of potential mitigation measures is also presented, highlighting critical knowledge gaps, challenges, and future research directions that require urgent draconian measures. This overview is intended to serve as a seminal reference and management pivot for enhancing global pollution mitigation policies, development of analytical models/methods, periodic monitoring of road dust-associated viruses, and the transport of other pathogenic microorganisms.
... Moreover, , has already confirmed the association between higher COVID-19 mortality rates and increased PM concentrations at the Harvard School of Public Health. This is consistent with the findings of previous studies on other viruses (Qin et al., 2020;Reche et al., 2018;Zhao et al., 2019). Lourenco et al. (Amato-Lourenço et al., 2022) detected the SARS-CoV-2 nucleocapsid in six samples and many more SARS-CoV-2 envelopes in 22 out of 38 total suspended particle samples (Table 4). ...
Road dust pollution is a complex atmospheric issue that poses a significant ecotoxicological threat to human health and the environment. The presence of viruses in road dust can put humans at risk of infection, as airborne viral particles are a potential synergist to respiratory infirmities, leading to widespread mortality and morbidity. This corroborates the increasing number of desk-based studies on the effects of road dust. However, the role of road dust in the spread and pathogenicity of viruses has scarcely been explored, and there is still no certainty regarding whether road dust participates in viral transmission or causes infectious diseases. Therefore, the current knowledge and mechanisms of road-dust-associated viruses and other pathogenic microorganisms are critically reviewed, highlighting the importance of keeping an eye out for road-dust-associated viruses, as they represent hotspots for viral transmission. In this overview, we evaluate the emissions, associated contaminants, and public health implications of exposure to road-dust-associated viruses. A summary of potential mitigation measures is also presented, highlighting critical knowledge gaps, challenges, and future research directions that require urgent draconian measures. This overview is intended to serve as a seminal reference and management pivot for enhancing global pollution mitigation policies, development of analytical models/methods, periodic monitoring of road dust-associated viruses, and the transport of other pathogenic microorganisms.
The dynamic relationship between microplastics (MPs) in the air and on the Earth’s surface involves both natural and anthropogenic forces. MPs are transported from the ocean to the air by bubble scavenging and seaspray formation and released from land sources by wind and human activities. Up to 8.6 megatons of MPs per year have been estimated to be in air above the oceans. They are distributed by wind, water and passive vectors and returned to the Earth’s surface via rainfall and passive deposition, but can escape to the stratosphere, where they may exist for months. Anthropogenic sprays, such as paints, agrochemicals, personal care and cosmetic products, and domestic and industrial procedures (e.g., air conditioning, vacuuming and washing, waste disposal, manufacture of plastic-containing objects) add directly to the airborne MP load, which is higher in internal than external air. Atmospheric MPs are less researched than those on land and in water, but, in spite of the major problem of lack of standard methods for determining MP levels, the clothing industry is commonly considered the main contributor to the external air pool, while furnishing fabrics, artificial ventilation devices, and presence and movement of human beings are the main source of indoor MPs. The majority of airbourne plastic particles are fibers and fragments; air currents enable them to reach remote environments, potentially traveling thousands of kilometers through the air, before being deposited in the various forms of precipitation (rain, snow, or “dust”). The increasing preoccupation of the populace and greater attention being paid to Industrial Ecology may help to reduce the concentration and spread of MPs and nanoparticles from domestic and industrial activities in the future.
Airborne viruses are ubiquitous and play critical roles in maintaining ecosystem balance, however, they remain unexplored. Here, it is aimed to demonstrate that highly diverse airborne viromes carry out specific metabolic functions and use different transmission modes under different air quality conditions. A total of 263.5‐Gb data are collected from 13 air samples for viral metagenomic analysis. After assembly and curation, a total of 12 484 viral contigs (1.5–184.2 kb) are assigned to 221 genus‐level clades belonging to 47 families, 19 orders, and 15 classes. The composition of viral communities is influenced by weather conditions, with the main biomarker being Caudoviricetes. The most dominant viruses in these air samples belong to the dsDNA Caudoviricetes (54.0%) and ssDNA Repensiviricetes (31.2%) classes. Twelve novel candidate viruses are identified at the order/family/genus levels by alignment of complete genomes and core genes. Notably, Caudoviricetes are highly prevalent in cloudy and smoggy air, whereas Repensiviricetes are highly dominant in sunny and rainy air. Diverse auxiliary metabolic genes of airborne viruses are mainly involved in deoxynucleotide synthesis, implying their unique roles in atmosphere ecosystem. These findings deepen the understanding of the meteorological impacts on viral composition, transmission mode, and ecological roles in the air that we breathe.
The dust cycle facilitates the exchange of particles among Earth's major systems, enabling dust to traverse ecosystems, cross geographic boundaries, and even move uphill against the natural flow of gravity. Dust in the atmosphere is composed of a complex and ever-changing mixture that reflects the evolving human footprint on the landscape. The emission, transport, and deposition of dust interacts with and connects Critical Zone processes at all spatial and temporal scales. Landscape properties, land use, and climatic factors influence the wind erosion of soil and nutrient loss, which alters the long-term ecological dynamics at erosional locations. Once in the atmosphere, dust particles influence the amount of solar radiation reaching Earth, and interact with longwave (terrestrial) radiation, with cascading effects on the climate system. Finally, the wet and dry deposition of particles influences ecosystem structure, composition, and function over both short and long-term scales. Tracking dust particles from source to sink relies on monitoring and measurement of the geochemical composition and size distribution of the particles, space-borne and ground-based remote sensing, and dust modeling. Dust is linked to human systems via land use and policies that contribute to dust emissions and the health-related consequences of particulate loads and composition. Despite the significant influence dust has in shaping coupled natural-human systems, it has not been considered a key component of the Critical Zone. Here we argue that dust particles should be included as a key component of the Critical Zone by outlining how dust interacts with and shapes Earth System processes from generation, through transport, to deposition. We synthesize current understanding from global research and identify critical data and knowledge gaps while showcasing case studies from North America.
Microbial communities are undergoing unprecedented dispersion and amalgamation across diverse ecosystems, thereby exerting profound and pervasive influences on microbial assemblages and ecosystem dynamics. This review delves into the phenomenon of community coalescence, offering an ecological overview that outlines its four-step process and elucidates the intrinsic interconnections in the context of community assembly. We examine pivotal mechanisms driving community coalescence, with a particular emphasis on elucidating the fates of both source and resident microbial communities and the consequential impacts on the ecosystem. Finally, we proffer recommendations to guide researchers in this rapidly evolving domain, facilitating deeper insights into the ecological ramifications of microbial community coalescence.
Studying airborne viral diversity in pristine, remote environments like the sub-Antarctic island South Georgia provides crucial insights into viral ecology and their role in sustaining unique ecosystems. Viruses influence microbial dynamics and nutrient cycles, which are vital for ecological balance and long-term ecosystem sustainability. We explored the community composition of airborne viral operational taxonomic units (vOTUs) of two sites in South Georgia, using various sampling devices and viral metagenomics. The Coriolis µ device (wet collection) was the most effective, yielding 30 viral scaffolds. Two-thirds of the scaffolds were from sea-level samples, indicating that location impacts viral diversity. Protein-based clustering of 39 vOTUs revealed similarities of 15 with known marine viruses, suggesting oceanic influence on the island's airborne viral community. Genes related to UV damage protection and photosynthesis from two airborne vOTUs were widely distributed in the major oceans, emphasizing the potential resilience in changing climates. Host predictions indicated associations with bacterial genera like Rickettsia, Myroides, and Bacteroidota. Some vOTUs matched viruses from extremophiles, indicating adaptations to harsh environments. This study provides a baseline for understanding the complexity and sustainability of airborne viral communities in remote ecosystems, underscoring the need for continued monitoring in the face of environmental change.
Life sciences research provides critical insights into disease processes and allows for the development of novel treatments and innovative medical technologies, thereby directly improving human health and technology. Despite the widely acknowledged relevance of life sciences, there has been a long-term pattern of low performance. This is due to inefficient teaching methods, as how a lesson is delivered influences the learners' level of understanding, among other things. Hence, the present study examined the experiences of life sciences teachers and learners in using IBL to enhance the academic performance of life science learners. This study was underpinned by the interpretivism paradigm, a qualitative approach, and a participatory research approach. The study population consisted of all life sciences learners in a rural school in the Amathole West district, Eastern Cape province of South Africa, from which 2 life sciences teachers and 14 learners were conveniently sampled. Data were collected using interviews, observations, and document reviews, and they were analysed using thematic analysis. The research findings revealed that enquiry-based learning has the potential to foster the development of critical thinking, problem-solving, and communication skills among life sciences learners. However, several issues make it difficult to successfully implement enquiry-based learning in the context of teaching and learning life sciences, including a lack of resources, time constraints, misreading of instructions, a lack of support or supervision, and a lack of pedagogical topic expertise among teachers. The study concludes that enquiry-based learning, when done right, can help learners understand life sciences concepts deeper and remember what they have learnt for a longer period.
Bacteriophages, or phages, are viruses that infect and replicate within bacterial hosts, playing a significant role in regulating microbial populations and ecosystem dynamics. However, phages from extreme environments such as polar regions remain relatively understudied due to challenges such as restricted ecosystem access and low biomass. Understanding the diversity, structure, and functions of polar phages is crucial for advancing our knowledge of the microbial ecology and biogeochemistry of these environments. In this review, we will explore the current state of knowledge on phages from the Arctic and Antarctic, focusing on insights gained from -omic studies, phage isolation, and virus-like particle abundance data. Metagenomic studies of polar environments have revealed a high diversity of phages with unique genetic characteristics, providing insights into their evolutionary and ecological roles. Phage isolation studies have identified novel phage–host interactions and contributed to the discovery of new phage species. Virus-like particle abundance and lysis rate data, on the other hand, have highlighted the importance of phages in regulating bacterial populations and nutrient cycling in polar environments. Overall, this review aims to provide a comprehensive overview of the current state of knowledge about polar phages, and by synthesizing these different sources of information, we can better understand the diversity, dynamics, and functions of polar phages in the context of ongoing climate change, which will help to predict how polar ecosystems and residing phages may respond to future environmental perturbations.
Invasions by eukaryotes dependent on environmentally acquired bacterial mutualists are often limited by the ability of bacterial partners to survive and establish free-living populations. Focusing on the model legume-rhizobium mutualism, we apply invasion biology hypotheses to explain how bacteriophages can impact the competitiveness of introduced bacterial mutualists. Predicting how phage-bacteria interactions affect invading eukaryotic hosts requires knowing the eco-evolutionary constraints of introduced and native microbial communities, as well as their differences in abundance and diversity. By synthesizing research from invasion biology, as well as bacterial, viral, and community ecology, we create a conceptual framework for understanding and predicting how phages can affect biological invasions through their effects on bacterial mutualists.
This chapter traces the progress of studies spanning many scientific disciplines and more than forty years of research. They all converge on the conclusion that life is a cosmic phenomenon. A comprehensive perspective on this field of scientific and philosophical knowledge is provided in twelve basic steps. Starting with the fact of the complex organic nature of interstellar dust, the author reflects on the implications of accepting the concept of cosmic life. He also considers the subject of exoplanets and the search for extraterrestrial life. The author then turns to the panspermia theory, which he has been instrumental in reviving and developing significantly since the 1970s. He argues for the cosmic origin of life using probability calculations and then discusses the direct spectroscopic evidence and other geological evidence for panspermia. The distribution of habitable exoplanets and the possibility of interplanetary transfer of life forms are discussed. This is complemented by the history of the research into meteorites, micrometeorites and cometary bacteria. Recent relevant studies on the controversial Polonnaruwa Meteorite are considered. With regard to panspermia, stratospheric sampling and the idea of diseases and pandemics from space are presented as important areas of existing and future research.KeywordsPanspermiaCosmic lifeCometsInterstellar dustMicrofossilsMeteoritesSocietal constraints
Bacteriophages, or phages, are viruses that infect and replicate within bacterial hosts, playing a significant role in regulating microbial populations and ecosystem dynamics. However, phages from extreme environments such as polar regions remain relatively understudied due to challenges like restricted ecosystem access and low biomass. Understanding the diversity, structure, and functions of polar phages is crucial for advancing our knowledge of the microbial ecology and biogeochemistry of these environments. In this review, we will explore the current state of knowledge on phages from the Arctic and Antarctic, focusing on insights gained from -omic studies, phage isolation, and virus-like particle abundance data. Metagenomic studies of polar environments have revealed a high diversity of phages with unique genetic characteristics, providing insights into their evolutionary and ecological roles. Phage isolation studies have identified novel phage-host interactions and contributed to the discovery of new phage species. Virus-like particle abundance and lysis rate data, on the other hand, have highlighted the importance of phages in regulating bacterial populations and nutrient cycling in polar environments. Overall, this review aims to provide a comprehensive overview of the current state of knowledge about polar phages, and by synthesizing these different sources of information, we can better understand the diversity, dynamics, and functions of polar phages in the context of ongoing climate change, which will help to predict how polar ecosystems and residing phages may respond to future environmental perturbations.
Unlabelled:
Bioaerosols play essential roles in the atmospheric environment and can affect human health. With a few exceptions (e.g., farm or rainforest environments), bioaerosol samples from wide-ranging environments typically have a low biomass, including bioaerosols from indoor environments (e.g., residential homes, offices, or hospitals), outdoor environments (e.g., urban or rural air). Some specialized environments (e.g., clean rooms, the Earth's upper atmosphere, or the international space station) have an ultra-low-biomass. This review discusses the primary sources of bioaerosols and influencing factors, the recent advances in air sampling techniques and the new generation sequencing (NGS) methods used for the characterization of low-biomass bioaerosol communities, and challenges in terms of the bias introduced by different air samplers when samples are subjected to NGS analysis with a focus on ultra-low biomass. High-volume filter-based or liquid-based air samplers compatible with NGS analysis are required to improve the bioaerosol detection limits for microorganisms. A thorough understanding of the performance and outcomes of bioaerosol sampling using NGS methods and a robust protocol for aerosol sample treatment for NGS analysis are needed. Advances in NGS techniques and bioinformatic tools will contribute toward the precise high-throughput identification of the taxonomic profiles of bioaerosol communities and the determination of their functional and ecological attributes in the atmospheric environment. In particular, long-read amplicon sequencing, viability PCR, and meta-transcriptomics are promising techniques for discriminating and detecting pathogenic microorganisms that may be active and infectious in bioaerosols and, therefore, pose a threat to human health.
Supplementary information:
The online version contains supplementary material available at 10.1007/s41745-023-00380-x.
Viruses are the most numerically abundant biological entities on Earth. As ubiquitous replicators of molecular information and agents of community change, viruses have potent effects on the life on Earth, and may play a critical role in human spaceflight, for life-detection missions to other planetary bodies and planetary protection. However, major knowledge gaps constrain our understanding of the Earth's virosphere: (1) the role viruses play in biogeochemical cycles, (2) the origin(s) of viruses and (3) the involvement of viruses in the evolution, distribution and persistence of life. As viruses are the only replicators that span all known types of nucleic acids, an expanded experimental and theoretical toolbox built for Earth's viruses will be pivotal for detecting and understanding life on Earth and beyond. Only by filling in these knowledge and technical gaps we will obtain an inclusive assessment of how to distinguish and detect life on other planetary surfaces. Meanwhile, space exploration requires life-support systems for the needs of humans, plants and their microbial inhabitants. Viral effects on microbes and plants are essential for Earth's biosphere and human health, but virus–host interactions in spaceflight are poorly understood. Viral relationships with their hosts respond to environmental changes in complex ways which are difficult to predict by extrapolating from Earth-based proxies. These relationships should be studied in space to fully understand how spaceflight will modulate viral impacts on human health and life-support systems, including microbiomes. In this review, we address key questions that must be examined to incorporate viruses into Earth system models, life-support systems and life detection. Tackling these questions will benefit our efforts to develop planetary protection protocols and further our understanding of viruses in astrobiology.
Risks associated with dust hazards are often underappreciated, a gap between the knowledge pool and public awareness that can be costly for impacted communities. This study reviews the emission sources and chemical, physical, and biological characteristics of airborne soil particles (dust) and their effects on human and environmental health and safety in the Pan-American region. American dust originates from both local sources (western United States, northern Mexico, Peru, Bolivia, Chile, and Argentina) and long-range transport from Africa and Asia. Dust properties, as well as the trends and interactions with criteria air pollutants, are summarized. Human exposure to dust is associated with adverse health effects, including asthma, allergies, fungal infections, and premature death. In the Americas, a well-documented and striking effect of soil dust is its association with Coccidioidomycosis, commonly known as Valley fever, an infection caused by inhalation of soil-dwelling fungi unique to this region. Besides human health, dust affects environmental health through nutrients that increase phytoplankton biomass, contaminants that diminish water supply and affect food (crops/fruits/vegetables and ready-to-eat meat), spread crop and marine pathogens, cause Valley fever among domestic and wild animals, transport heavy metals, radionuclides and microplastics, and reduce solar and wind power generation. Dust is also a safety hazard to road transportation and aviation, in the southwestern US where blowing dust is one of the deadliest weather hazards. To mitigate the harmful effects, coordinated regional and international efforts are needed to enhance dust observations and prediction capabilities, soil conservation measures, and Valley fever and other disease surveillance.
The density, form, and dimensions of urban morphology are important for healthy living conditions in cities, especially if they are related to the climate and air pollution. Morphology and environmental conditions determine the relationship between open and built space, the width of street spaces, the aerodynamic characteristics of wind currents, albedo, and the retention of pollutants, as well as determining the radiative exchange with the atmosphere. Studies on the COVID-19 pandemic have focused on the assumption of a possible relationship between the spread of the SARS-CoV-2 virus and the presence and concentration of airborne particulate matter (PM10 and PM2.5). This paper focuses on the research of indoor air quality (IAQ) in two schools with naturally ventilated classrooms in Ljubljana, Slovenia. The presence of particulate matter (PM2.5 and PM10) and the concentration of CO2 were studied, along with other microclimatic conditions, e.g., ambient temperature, relative humidity, air pressure, and wind conditions. These were compared and assessed via analysis of variance (ANOVA) and Duncan’s post hoc test. The main concern was to see how effective different ventilation strategies are, as well as how the openings in the classroom impact the concentrations of CO2 relative to the concentrations of PM2.5 and PM10 particles as a side effect of these ventilation strategies. The inconsistent application of recommended COVID-19 ventilation strategies suggests that IAQ in naturally ventilated classrooms is highly determined by individual perceptions of indoor air quality. The results also suggest that the IAQ is significantly affected by the schools’ urban environment; however, this is not considered within the national COVID-19 ventilation recommendations. Future ventilation guidelines for pandemics should also include the urban environment as a risk factor for inadequate IAQ, instead of focusing solely on pathogen characteristics.
Viruses are the most abundant biological entity in the ocean and infect a wide range of microbial life across bacteria, archaea, and eukaryotes. In this essay, we take a journey across several orders of magnitude in the scales of biological organization, time, and space of host–virus interactions in the ocean, aiming to shed light on their ecological relevance. We start from viruses infecting microbial host cells by delivering their genetic material in seconds across nanometer-size membranes, which highjack their host’s metabolism in a few minutes to hours, leading to a profound transcriptomic and metabolic rewiring. The outcome of lytic infection leads to a release of virions and signaling molecules that can reach neighboring cells a few millimeters away, resulting in a population whose heterogeneous infection level impacts the surrounding community for days. These population dynamics can leave unique metabolic and biogeochemical fingerprints across scales of kilometers and over several decades. One of the biggest challenges in marine microbiology is to assess the impact of viruses across these scales, from the single cell to the ecosystem level. Here, we argue that the advent of new methodologies and conceptual frameworks represents an exciting time to pursue these efforts and propose a set of important challenges for the field. A better understanding of host–virus interactions across scales will inform models of global ocean ecosystem function in different climate change scenarios.
Recent works on wall-bounded flows have corroborated the coexistence of wall-attached eddies, whose statistical features are predicted through Townsend's attached-eddy hypothesis (AEH), and very-large-scale motions (VLSMs). Furthermore, it has been shown that the presence of wall-attached eddies within the logarithmic layer is linked to the appearance of an inverse-power-law region in the streamwise velocity energy spectra, upon significant separation between outer and viscous scales. In this work, a near-neutral atmospheric surface layer is probed with wind light detection and ranging to investigate the contributions to the streamwise velocity energy associated with wall-attached eddies and VLSMs for a very-high-Reynolds-number boundary layer. Energy and linear coherence spectra (LCS) of the streamwise velocity are interrogated to identify the spectral boundaries associated with eddies of different typologies. Inspired by the AEH, an analytical model for the LCS associated with wall-attached eddies is formulated. The experimental results show that the identification of the wall-attached-eddy energy contribution through the analysis of the energy spectra leads to an underestimate of the associated spectral range, maximum height attained and turbulence intensity. This feature is due to the overlap of the energy associated with VLSMs obscuring the inverse-power-law region. The LCS analysis estimates wall-attached eddies with a streamwise/wall-normal ratio of about 14.3 attaining a height of about 30 % of the outer scale of turbulence.
Viruses are the most numerically abundant biological entities on Earth. As ubiquitous replicators of information molecules and agents of community change, viruses have potent effects on life on Earth and may play a critical role in human spaceflight missions, life detection missions to other planetary bodies, and in planetary protection. However, major knowledge gaps constrain our understanding of the Earth’s virosphere: 1) the role viruses play in biogeochemical cycles, 2) the origin(s) of viruses, and 3) the involvement of viruses in the evolution, distribution, and persistence of life. As viruses are the only replicators that span all known types of nucleic acids, an expanded experimental and theoretical toolbox built for Earth’s viruses will be pivotal for detecting and understanding life on Earth and beyond. Only by filling in these knowledge and technical gaps will we obtain an inclusive assessment of how to distinguish and detect life on other planetary surfaces. Meanwhile, space exploration requires life-support systems for the needs of humans, plants, and their microbial inhabitants. Viral effects on microbes and plants are essential for Earth’s biosphere and human health, but virus-host interactions in spaceflight are poorly understood. Viral relationships with their hosts respond to environmental changes in complex ways which are difficult to predict by extrapolating from Earth-based proxies. These relationships must therefore be studied in space to fully understand how spaceflight will modulate viral impacts on human health and life-support systems, including microbiomes. This review addresses key questions that must be examined to incorporate viruses into Earth system models, life-support systems, and life detection. Further, the results of tackling these questions will help in our efforts to develop planetary protection protocols and further our understanding of viruses in astrobiology.
Virus particles are highly abundant in seawater and, on average, outnumber microbial cells approximately 10-fold at the surface and 16-fold in deeper waters; yet, this relationship varies across environments. Here, we examine the influence of a suite of environmental variables, including nutrient concentrations, salinity and temperature, on the relationship between the abundances of viruses and prokaryotes over a broad range of spatial and temporal scales, including along a track from the Northwest Atlantic to the Northeast Pacific via the Arctic Ocean, and in the coastal waters of British Columbia, Canada. Models of varying complexity were tested and compared for best fit with the Akaike Information Criterion, and revealed that nitrogen and phosphorus concentrations, as well as prokaryote abundances, either individually or combined, had significant effects on viral abundances in all but hypoxic environments, which were only explained by a combination of physical and chemical factors. Nonetheless, multivariate models of environmental variables showed high explanatory power, matching or surpassing that of prokaryote abundance alone. Incorporating both environmental variables and prokaryote abundances into multivariate models significantly improved the explanatory power of the models, except in hypoxic environments. These findings demonstrate that environmental factors could be as important as, or even more important than, prokaryote abundance in describing viral abundance across wide-ranging marine environments
Viruses, once thought of only as purveyors of disease, take centre stage, from the human microbiome to the oceans, as archives of global diversity and drivers of biogeochemical cycles
Atmospheric aerosol particles of biological origin are a very diverse group of biological materials and structures, including microorganisms, dispersal units, fragments and excretions of biological organisms. In recent years, the impact of biological aerosol particles on atmospheric processes has been studied with increasing intensity, and a wealth of new information and insights has been gained. This review outlines the current knowledge on major categories of primary biological aerosol particles (PBAP): bacteria and archaea, fungal spores and fragments, pollen, viruses, algae and cyanobacteria, biological crusts and lichens and others like plant or animal fragments and detritus. We give an overview of sampling methods and physical, chemical and biological techniques for PBAP analysis (cultivation, microscopy, DNA/RNA analysis, chemical tracers, optical and mass spectrometry, etc.). Moreover, we address and summarise the current understanding and open questions concerning the influence of PBAP on the atmosphere and climate, i.e. their optical properties and their ability to act as ice nuclei (IN) or cloud condensation nuclei (CCN). We suggest that the following research activities should be pursued in future studies of atmospheric biological aerosol particles: (1) develop efficient and reliable analytical techniques for the identification and quantification of PBAP; (2) apply advanced and standardised techniques to determine the abundance and diversity of PBAP and their seasonal variation at regional and global scales (atmospheric biogeography); (3) determine the emission rates, optical properties, IN and CCN activity of PBAP in field measurements and laboratory experiments; (4) use field and laboratory data to constrain numerical models of atmospheric transport, transformation and climate effects of PBAP.
Primary Biological Aerosol Particles (PBAPs), including bacteria, spores and pollen, are essential for the spread of organisms and disease in the biosphere, and numerous studies have suggested that they may be important for atmospheric processes, including the formation of clouds and precipitation. The atmospheric abundance and size distribution of PBAPs, however, are largely unknown. At a semi-urban site in Mainz, Germany we used an Ultraviolet Aerodynamic Particle Sizer (UV-APS) to measure Fluorescent Biological Aerosol Particles (FBAPs), which provide an estimate of viable bioaerosol particles and can be regarded as an approximate lower limit for the actual abundance of PBAPs. Fluorescence of non-biological aerosol components are likely to influence the measurement results obtained for fine particles (<1 μm), but not for coarse particles (1–20 μm).
Averaged over the four-month measurement period (August–December 2006), the mean number concentration of coarse FBAPs was ~3×10−2 cm−3, corresponding to ~4% of total coarse particle number. The mean mass concentration of FBAPs was ~1μg m−3, corresponding to ~20% of total coarse particle mass. The FBAP number size distributions exhibited alternating patterns with peaks at various diameters. A pronounced peak at ~3 μm was essentially always observed and can be described by the following campaign-average lognormal fit parameters: geometric mean diameter 3.2 μm, geometric standard deviation 1.3, number concentration 1.6×10−2 cm−3. This peak is likely due to fungal spores or agglomerated bacteria, and it exhibited a pronounced diel cycle (24-h) with maximum intensity during early/mid-morning. FBAP peaks around ~1.5 μm, ~5 μm, and ~13 μm were also observed, but less pronounced and less frequent. These may be single bacterial cells, larger fungal spores, and pollen grains, respectively.
The observed number concentrations and characteristic sizes of FBAPs are consistent with microscopic, biological and chemical analyses of PBAPs in aerosol filter samples. To our knowledge, however, this is the first exploratory study reporting continuous online measurements of bioaerosol particles over several months and a range of characteristic size distribution patterns with a persistent bioaerosol peak at ~3 μm. The measurement results confirm that PBAPs account for a substantial proportion of coarse aerosol particle number and mass in continental boundary layer air. Moreover, they suggest that the number concentration of viable bioparticles is dominated by fungal spores or agglomerated bacteria with aerodynamic diameters around 3 μm rather than single bacterial cells with diameters around 1 μm.
The discovery of the numerical importance of viruses in a variety of (aquatic) ecosystems has changed our perception of their importance in microbial processes. Bacteria and Archaea undoubtedly represent the most abundant cellular life forms on Earth and past estimates of viral numbers (represented mainly by viruses infecting prokaryotes) have indicated abundances at least one order of magnitude higher than that of their cellular hosts. Such dominance has been reflected most often by the virus-to-prokaryote ratio (VPR), proposed as a proxy for the relationship between viral and prokaryotic communities. VPR values have been discussed in the literature to express viral numerical dominance (or absence of it) over their cellular hosts, but the ecological meaning and interpretation of this ratio has remained somewhat nebulous or contradictory. We gathered data from 210 publications (and additional unpublished data) on viral ecology with the aim of exploring VPR. The results are presented in three parts: the first consists of an overview of the minimal, maximal and calculated average VPR values in an extensive variety of different environments. Results indicate that VPR values fluctuate over six orders of magnitude, with variations observed within each ecosystem. The second part investigates the relationship between VPR and other indices, in order to assess whether VPR can provide insights into virus-host relationships. A positive relationship was found between VPR and viral abundance (VA), frequency of visibly infected cells (FVIC), burst size (BS), frequency of lysogenic cells (FLC) and chlorophyll a (Chl a) concentration. An inverse relationship was detected between VPR and prokaryotic abundance (PA) (in sediments), prokaryotic production (PP) and virus-host contact rates (VCR) as well as salinity and temperature. No significant relationship was found between VPR and viral production (VP), fraction of mortality from viral lysis (FMVL), viral decay rate (VDR), viral turnover (VT) or depth. Finally, we summarize our results by proposing two scenarios in two contrasting environments, based on current theories on viral ecology as well as the present results. We conclude that since VPR fluctuates in every habitat for different reasons, as it is linked to a multitude of factors related to virus-host dynamics, extreme caution should be used when inferring relationships between viruses and their hosts. Furthermore, we posit that the VPR is only useful in specific, controlled conditions, e.g. for the monitoring of fluctuations in viral and host abundance over time.
Marine viruses are critical drivers of ocean biogeochemistry, and their abundances vary spatiotemporally in the global oceans, with upper estimates exceeding 108 per ml. Over many years, a consensus has emerged that virus abundances are typically tenfold higher than microbial cell abundances. However, the true explanatory power of a linear relationship and its robustness across diverse ocean environments is unclear. Here, we compile 5,671 microbial cell and virus abundance estimates from 25 distinct marine surveys and find substantial variation in the virus-to-microbial cell ratio, in which a 10:1 model has either limited or no explanatory power. Instead, virus abundances are better described as nonlinear, power-law functions of microbial cell abundances. The fitted scaling exponents are typically less than 1, implying that the virus-to-microbial cell ratio decreases with microbial cell density, rather than remaining fixed. The observed scaling also implies that viral effect sizes derived from ‘representative’ abundances require substantial refinement to be extrapolated to regional or global scales.
Paper available for download at: http://arjournals.annualreviews.org/eprint/eYPsIaEsTKMUkb7J5njR/full/10.1146/annurev-virology-031413-085540
Viral ecology is a rapidly progressing area of research, as molecular methods have improved significantly for targeted research on specific populations and whole communities. To interpret and synthesize global viral diversity and distribution, it is feasible to assess whether macroecology concepts can apply to marine viruses. We review how viral and host life history and physical properties can influence viral distribution in light of biogeography and metacommunity ecology paradigms. We highlight analytical approaches that can be applied to emerging global data sets and meta-analyses to identify individual taxa with global influence and drivers of emergent properties that influence microbial community structure by drawing on examples across the spectrum of viral taxa, from RNA to ssDNA and dsDNA viruses.
Significance
Marine viruses constitute a major ecological and evolutionary driving force in marine ecosystems and are responsible for cycling of major nutrients; however, their dispersal mechanisms remain underexplored. By using one of the most established host–pathogen planktonic model systems we provide strong evidence that specific viruses of marine coccolithophores can be transmitted and stay infective as marine aerosols. Being transported by the wind, phytoplankton viruses can be conveyed long distances and transmit the infection to remote locations to which coccolithophore blooms can be extended. We show that this effective transmission mechanism that has been studied in human, animal, and plant diseases could play an important role in host–virus dynamics during phytoplankton blooms in the ocean.
Airborne transport of microbes may play a central role in microbial dispersal, the maintenance of diversity in aquatic systems and in meteorological processes such as cloud formation. Yet, there is almost no information about the abundance and fate of microbes over the oceans, which cover >70% of the Earth's surface and are the likely source and final destination of a large fraction of airborne microbes. We measured the abundance of microbes in the lower atmosphere over a transect covering 17° of latitude in the North Atlantic Ocean and derived estimates of air-sea exchange of microorganisms from meteorological data. The estimated load of microorganisms in the atmospheric boundary layer ranged between 6 × 104 and 1.6 × 107 microbes per m2 of ocean, indicating a very dynamic air-sea exchange with millions of microbes leaving and entering the ocean per m2 every day. Our results show that about 10% of the microbes detected in the boundary layer were still airborne 4 days later and that they could travel up to 11,000 km before they entered the ocean again. The size of the microbial pool hovering over the North Atlantic indicates that it could play a central role in the maintenance of microbial diversity in the surface ocean and contribute significantly to atmospheric processes.
Action at a Distance
Snowfall in the Sierra Nevada provides a large fraction of the water that California receives as precipitation. Knowing what factors influence the amount of snow that falls is thus critical for projecting how water availability may change in the future. Aerosols have an important effect on cloud processes and precipitation. Creamean et al. (p. 1572 , published online 28 February) found that dust and biological aerosols originating from as far away as the Sahara facilitate ice nuclei formation and ice-induced precipitation in the Sierra Nevada and show how dust and biological articles from places as distant as Africa and Asia can influence precipitation over the western United States.
The planetary boundary layer (PBL) height is a key variable in climate modeling and has an enormous influence on air pollution. A method based on the wavelet covariance transform (WCT) applied to lidar data is tested in this paper as an automated and nonsupervised method to obtain the PBL height. The parcel and the Richardson number methods applied to radiosounding data and the parcel method applied to microwave radiometer temperature profiles are used as independent measurements of the PBL height in order to optimize the parameters required for its detection using the WCT method under different atmospheric conditions. This optimization allows for a one-year statistical analysis of the PBL height at midday over Granada (southeastern Spain) from lidar data. The PBL height showed a seasonal cycle, with higher values in summer and spring while lower values were found in winter and autumn. The annual mean was 1.7 ± 0.5 km a.s.l. during the study period. The relationship of the PBL height with aerosol properties is also analyzed for the one-year period. © 2012. American Geophysical Union.
Viral abundance and processes in the water column and sediments are well studied for some systems; however, we know relatively little about virus–host interactions on particles and how particles influence these interactions. Here we review virus–prokaryote interactions on inorganic and organic particles in the water column. Profiting from recent methodological progress, we show that confocal laser scanning microscopy in combination with lectin and nucleic acid staining is one of the most powerful methods to visualize the distribution of viruses and their hosts on particles such as organic aggregates. Viral abundance on suspended matter ranges from 105 to 1011 ml–1. The main factors controlling viral abundance are the quality, size and age of aggregates and the exposure time of viruses to aggregates. Other factors such as water residence time likely act indirectly. Overall, aggregates appear to play a role of viral scavengers or reservoirs rather than viral factories. Adsorption of viruses to organic aggregates or inorganic particles can stimulate growth of the free-living prokaryotic community, e.g. by reducing viral lysis. Such mechanisms can affect microbial diversity, food web structure and biogeochemical cycles. Viral lysis of bacterio- and phytoplankton influences the formation and fate of aggregates and can, for example, result in a higher stability of algal flocs. Thus, viruses also influence carbon export; however, it is still not clear whether they short-circuit or prime the biological pump. Throughout this review, emphasis has been placed on defining general problems and knowledge gaps in virus–particle interactions and on providing avenues for further research, particularly those linked to global change.
A B S T R A C T Atmospheric aerosol particles of biological origin are a very diverse group of biological materials and structures, including microorganisms, dispersal units, fragments and excretions of biological organisms. In recent years, the impact of biological aerosol particles on atmospheric processes has been studied with increasing intensity, and a wealth of new information and insights has been gained. This review outlines the current knowledge on major categories of primary biological aerosol particles (PBAP): bacteria and archaea, fungal spores and fragments, pollen, viruses, algae and cyanobacteria, biological crusts and lichens and others like plant or animal fragments and detritus. We give an overview of sampling methods and physical, chemical and biological techniques for PBAP analysis (cultivation, microscopy, DNA/RNA analysis, chemical tracers, optical and mass spectrometry, etc.). Moreover, we address and summarise the current understanding and open questions concerning the influence of PBAP on the atmosphere and climate, i.e. their optical properties and their ability to act as ice nuclei (IN) or cloud condensation nuclei (CCN). We suggest that the following research activities should be pursued in future studies of atmospheric biological aerosol particles: (1) develop efficient and reliable analytical techniques for the identification and quantification of PBAP; (2) apply advanced and standardised techniques to determine the abundance and diversity of PBAP and their seasonal variation at regional and global scales (atmospheric biogeography); (3) determine the emission rates, optical properties, IN and CCN activity of PBAP in field measurements and laboratory experiments; (4) use field and laboratory data to constrain numerical models of atmospheric transport, transformation and climate effects of PBAP.
The atmospheric dispersion of bacteria over long distances is an important facet of microbial ecology. Certain groups of dispersed bacteria can adapt to their new location and affect established ecosystems. Aeolian dust particles are known to be carriers of microbes but further research is needed to expand our understanding of this field of microbiology. Here we showed the potential of aeolian dust to global migration of bacterial cells. We demonstrated the presence of microbial cells on dust particles directly by bio-imaging. Bacterial abundance on dust particles declined from 10(5) to less than 10(3) cells/m3 as the dust event subsided. Taxonomically diverse bacteria were identified by 16S rRNA gene sequencing and some of these bacteria retained growth potential. Our results confirm that bacteria can attach to aeolian dust particles and they have the potential to migrate globally during dust events and thus can contribute to the diversity of downwind ecosystems.
We use the Total Ozone Mapping Spectrometer (TOMS) sensor on the Nimbus 7 satellite to map the global distribution of major atmospheric dust sources with the goal of identifying common environmental characteristics. The largest and most persistent sources are located in the Northern Hemisphere, mainly in a broad "dust belt" that extends from the west coast of North Africa, over the Middle East, Central and South Asia, to China. There is remarkably little large-scale dust activity outside this region. In particular, the Southern Hemisphere is devoid of major dust activity. Dust sources, regardless of size or strength, can usually be associated with topographical lows located in arid regions with annual rainfall under 200-250 mm. Although the source regions themselves are arid or hyperarid, the action of water is evident from the presence of ephemeral streams, rivers, lakes, and playas. Most major sources have been intermittently flooded through the Quaternary as evidenced by deep alluvial deposits. Many sources are associated with areas where human impacts are well documented, e.g., the Caspian and Aral Seas, Tigris-Euphrates River Basin, southwestern North America, and the loess lands in China. Nonetheless, the largest and most active sources are located in truly remote areas where there is little or no human activity. Thus, on a global scale, dust mobilization appears to be dominated by natural sources. Dust activity is extremely sensitive to many environmental parameters. The identification of major sources will enable us to focus on critical regions and to characterize emission rates in response to environmental conditions. With such knowledge we will be better able to improve global dust models and to assess the effects of climate change on emissions in the future. It will also facilitate the interpretation of the paleoclimate record based on dust contained in ocean sediments and ice cores.
Airborne viruses are expected to be ubiquitous in the atmosphere but they still remain poorly understood. This study investigated the temporal and spatial dynamics of airborne viruses and their genotypic characteristics in air samples collected from three distinct land use types (a residential district [RD], a forest [FR], and an industrial complex [IC]) and from rainwater samples freshly precipitated at the RD site (RD-rain). Viral abundance exhibited a seasonal fluctuation in the range between 1.7 × 10(6) and 4.0 × 10(7) viruses m(-3), which increased from autumn to winter and decreased toward spring, but no significant spatial differences were observed. Temporal variations in viral abundance were inversely correlated with seasonal changes in temperature and absolute humidity. Metagenomic analysis of air viromes amplified by rolling-circle phi29 polymerase-based random hexamer priming indicated the dominance of plant-associated single-stranded DNA (ssDNA) geminivirus-related viruses, followed by animal-infecting circovirus-related sequences, with low numbers of nanoviruses and microphages-related genomes. Particularly, the majority of the geminivirus-related viruses were closely related to ssDNA mycoviruses that infect plant-pathogenic fungi. Phylogenetic analysis based on the replication initiator protein sequence indicated that the airborne ssDNA viruses were distantly related to known ssDNA viruses, suggesting that a high diversity of viruses were newly discovered. This research is the first to report the seasonality of airborne viruses and their genetic diversity, which enhances our understanding of viral ecology in temperate regions.
Over the past two decades, marine virology has progressed from a curiosity to an intensely studied topic of critical importance to oceanography. At concentrations of approximately 10 million viruses per milliliter of surface seawater, viruses are the most abundant biological entities in the oceans. The majority of these viruses are phages (viruses that infect bacteria). Through lysing their bacterial hosts, marine phages control bacterial abundance, affect community composition, and impact global biogeochemical cycles. In addition, phages influence their hosts through selection for resistance, horizontal gene transfer, and manipulation of bacterial metabolism. Recent work has also demonstrated that marine phages are extremely diverse and can carry a variety of auxiliary metabolic genes encoding critical ecological functions. This review is structured as a scientific "truth or dare," revealing several well-established "truths" about marine viruses and presenting a few "dares" for the research community to undertake in future studies.
Remote lakes are usually unaffected by direct human influence, yet they receive inputs of atmospheric pollutants, dust, and other aerosols, both inorganic and organic. In remote, alpine lakes, these atmospheric inputs may influence the pool of dissolved organic matter, a critical constituent for the biogeochemical functioning of aquatic ecosystems. Here, to assess this influence, we evaluate factors related to aerosol deposition, climate, catchment properties, and microbial constituents in a global dataset of 86 alpine and polar lakes. We show significant latitudinal trends in dissolved organic matter quantity and quality, and uncover new evidence that this geographic pattern is influenced by dust deposition, flux of incident ultraviolet radiation, and bacterial processing. Our results suggest that changes in land use and climate that result in increasing dust flux, ultraviolet radiation, and air temperature may act to shift the optical quality of dissolved organic matter in clear, alpine lakes.
Dormancy is a bet-hedging strategy used by a variety of organisms to overcome unfavorable environmental conditions. By entering a reversible state of low metabolic activity, dormant individuals become members of a seed bank, which can determine community dynamics in future generations. Although microbiologists have documented dormancy in both clinical and natural settings, the importance of seed banks for the diversity and functioning of microbial communities remains untested. Here, we develop a theoretical model demonstrating that microbial communities are structured by environmental cues that trigger dormancy. A molecular survey of lake ecosystems revealed that dormancy plays a more important role in shaping bacterial communities than eukaryotic microbial communities. The proportion of dormant bacteria was relatively low in productive ecosystems but accounted for up to 40% of taxon richness in nutrient-poor systems. Our simulations and empirical data suggest that regional environmental cues and dormancy synchronize the composition of active communities across the landscape while decoupling active microbes from the total community at local scales. Furthermore, we observed that rare bacterial taxa were disproportionately active relative to common bacterial taxa, suggesting that microbial rank-abundance curves are more dynamic than previously considered. We propose that repeated transitions to and from the seed bank may help maintain the high levels of microbial biodiversity that are observed in nearly all ecosystems.
Bacteria are constantly being transported through the atmosphere, which may have implications for human health, agriculture, cloud formation, and the dispersal of bacterial species. We simulated the global transport of bacterial cells, represented as 1mum diameter spherical solid particle tracers, in a chemistry-climate model. We investigated the factors influencing residence time and distribution of the particles, including emission region, CCN activity and removal by ice-phase precipitation. The global distribution depends strongly on the assumptions made about uptake into cloud droplets and ice. The transport is also affected, to a lesser extent, by the emission region and by season. We examine the potential for exchange of bacteria between ecosystems and obtain rough estimates of the flux from each ecosystem by using an optimal estimation technique, together with a new compilation of available observations described in a companion paper. Globally, we estimate the total emissions of bacteria to the atmosphere to be 1400 Gg per year with an upper bound of 4600 Gg per year, originating mainly from grasslands, shrubs and crops. In order to improve understanding of this topic, more measurements of the bacterial content of the air will be necessary. Future measurements in wetlands, sandy deserts, tundra, remote glacial and coastal regions and over oceans will be of particular interest.
Transparent exopolymer particles (TEP) are the most ubiquitous gel particles in the ocean and form abiotically from dissolved precursors. Although these particles can accumulate at the ocean surface, being thus exposed to intense sunlight, the role of solar radiation for the assembly and degradation of TEP is unknown. In this study, we experimentally determined the effects of visible and ultraviolet B (UVB) radiation on (1) TEP degradation (photolysis experiments), (2) TEP assembly from dissolved polymers (photoinhibition experiments) and (3) TEP release by microorganisms. Solar radiation, particularly in the UVB range, caused significant TEP photolysis, with loss rates from 27 to 34% per day. Dissolved polysaccharides did not increase in parallel. No TEP were formed under UVB, visible or dark conditions, indicating that light does not promote TEP assembly. UVB radiation enhanced TEP release by microorganisms, possibly due to cell deaths, or as a protective measure. Increases in UVB may lead to enhanced TEP photolysis in the ocean, with further consequences for TEP dynamics and, ultimately, sea-air gas exchange.
Publicación online disponible en: http://www.icm.csic.es/scimar/index.php Flow cytometry is rapidly becoming a routine methodology in aquatic microbial ecology. The combination of simple to use bench-top flow cytometers and highly fluorescent nucleic acid stains allows fast and easy determination of microbe abundance in the plankton of lakes and oceans. The different dyes and protocols used to stain and count planktonic bacteria as well as the equipment in use are reviewed, with special attention to some of the problems encountered in daily routine practice such as fixation, staining and absolute counting. One of the main advantages of flow cytometry over epifluorescence microscopy is the ability to obtain cell-specific measurements in large numbers of cells with limited effort. We discuss how this characteristic has been used for differentiating photosynthetic from non-photosynthetic prokaryotes, for measuring bacterial cell size and nucleic acid content, and for estimating the relative activity and physiological state of each cell. We also describe how some of the flow cytometrically obtained data can be used to characterize the role of microbes on carbon cycling in the aquatic environment and we prospect the likely avenues of progress in the study of planktonic prokaryotes through the use of flow cytometry. This work has been supported by grants MAS3-CT95- 0016 (MEDEA) and MAS3-CT97-0154 (MIDAS). Peer reviewed
Bacteria and fungi are ubiquitous in the atmosphere. The diversity and abundance of airborne microbes may be strongly influenced
by atmospheric conditions or even influence atmospheric conditions themselves by acting as ice nucleators. However, few comprehensive
studies have described the diversity and dynamics of airborne bacteria and fungi based on culture-independent techniques.
We document atmospheric microbial abundance, community composition, and ice nucleation at a high-elevation site in northwestern
Colorado. We used a standard small-subunit rRNA gene Sanger sequencing approach for total microbial community analysis and
a bacteria-specific 16S rRNA bar-coded pyrosequencing approach (4,864 sequences total). During the 2-week collection period,
total microbial abundances were relatively constant, ranging from 9.6 × 105 to 6.6 × 106 cells m−3 of air, and the diversity and composition of the airborne microbial communities were also relatively static. Bacteria and
fungi were nearly equivalent, and members of the proteobacterial groups Burkholderiales and Moraxellaceae (particularly the genus Psychrobacter) were dominant. These taxa were not always the most abundant in freshly fallen snow samples collected at this site. Although
there was minimal variability in microbial abundances and composition within the atmosphere, the number of biological ice
nuclei increased significantly during periods of high relative humidity. However, these changes in ice nuclei numbers were
not associated with changes in the relative abundances of the most commonly studied ice-nucleating bacteria.
Barriers to dispersal between populations allow them to diverge through local adaptation or random genetic drift. High-resolution
multilocus sequence analysis revealed that, on a global scale, populations of hyperthermophilic microorganisms are isolated
from one another by geographic barriers and have diverged over the course of their recent evolutionary history. The identification
of a biogeographic pattern in the archaeon Sulfolobus challenges the current model of microbial biodiversity in which unrestricted dispersal constrains the development of global
species richness.
The finding that total viral abundance is higher than total prokaryotic abundance and that a significant fraction of the prokaryotic community is infected with phages in aquatic systems has stimulated research on the ecology of prokaryotic viruses and their role in ecosystems. This review treats the ecology of prokaryotic viruses ('phages') in marine, freshwater and soil systems from a 'virus point of view'. The abundance of viruses varies strongly in different environments and is related to bacterial abundance or activity suggesting that the majority of the viruses found in the environment are typically phages. Data on phage diversity are sparse but indicate that phages are extremely diverse in natural systems. Lytic phages are predators of prokaryotes, whereas lysogenic and chronic infections represent a parasitic interaction. Some forms of lysogeny might be described best as mutualism. The little existing ecological data on phage populations indicate a large variety of environmental niches and survival strategies. The host cell is the main resource for phages and the resource quality, i.e., the metabolic state of the host cell, is a critical factor in all steps of the phage life cycle. Virus-induced mortality of prokaryotes varies strongly on a temporal and spatial scale and shows that phages can be important predators of bacterioplankton. This mortality and the release of cell lysis products into the environment can strongly influence microbial food web processes and biogeochemical cycles. Phages can also affect host diversity, e.g., by 'killing the winner' and keeping in check competitively dominant species or populations. Moreover, they mediate gene transfer between prokaryotes, but this remains largely unknown in the environment. Genomics or proteomics are providing us now with powerful tools in phage ecology, but final testing will have to be performed in the environment.
Primers were designed to amplify a 592-bp region within a conserved structural gene (g20) found in some cyanophages. The goal was to use this gene as a proxy to infer genetic richness in natural cyanophage communities and to determine if sequences were more similar in similar environments. Gene products were amplified from samples from the Gulf of Mexico, the Arctic, Southern, and Northeast and Southeast Pacific Oceans, an Arctic cyanobacterial mat, a catfish production pond, lakes in Canada and Germany, and a depth of ca. 3,246 m in the Chuckchi Sea. Amplicons were separated by denaturing gradient gel electrophoresis, and selected bands were sequenced. Phylogenetic analysis revealed four previously unknown groups of g20 clusters, two of which were entirely found in freshwater. Also, sequences with >99% identities were recovered from environments that differed greatly in temperature and salinity. For example, nearly identical sequences were recovered from the Gulf of Mexico, the Southern Pacific Ocean, an Arctic freshwater cyanobacterial mat, and Lake Constance, Germany. These results imply that closely related hosts and the viruses infecting them are distributed widely across environments or that horizontal gene exchange occurs among phage communities from very different environments. Moreover, the amplification of g20 products from deep in the cyanobacterium-sparse Chuckchi Sea suggests that this primer set targets bacteriophages other than those infecting cyanobacteria.
The development of sensitive nucleic acid stains, in combination with flow cytometric techniques, has allowed the identification
and enumeration of viruses in aquatic systems. However, the methods used in flow cytometric analyses of viruses have not been
consistent to date. A detailed evaluation of a broad range of sample preparations to optimize counts and to promote the consistency
of methods used is presented here. The types and concentrations of dyes, fixatives, dilution media, and additives, as well
as temperature and length of incubation, dilution factor, and storage conditions were tested. A variety of different viruses,
including representatives of phytoplankton viruses, cyanobacteriophages, coliphages, marine bacteriophages, and natural mixed
marine virus communities were examined. The conditions that produced optimal counting results were fixation with glutaraldehyde
(0.5% final concentration, 15 to 30 min), freezing in liquid nitrogen, and storage at −80°C. Upon thawing, samples should
be diluted in Tris-EDTA buffer (pH 8), stained with SYBR Green I (a 5 × 10−5 dilution of commercial stock), incubated for 10 min in the dark at 80°C, and cooled for 5 min prior to analysis. The results
from examinations of storage conditions clearly demonstrated the importance of low storage temperatures (at least −80°C) to
prevent strong decreases (occasionally 50 to 80% of the total) in measured total virus abundance with time.
Viruses exist wherever life is found. They are a major cause of mortality, a driver of global geochemical cycles and a reservoir of the greatest genetic diversity on Earth. In the oceans, viruses probably infect all living things, from bacteria to whales. They affect the form of available nutrients and the termination of algal blooms. Viruses can move between marine and terrestrial reservoirs, raising the spectre of emerging pathogens. Our understanding of the effect of viruses on global systems and processes continues to unfold, overthrowing the idea that viruses and virus-mediated processes are sidebars to global processes.
We review the biogeography of microorganisms in light of the biogeography of macroorganisms. A large body of research supports the idea that free-living microbial taxa exhibit biogeographic patterns. Current evidence confirms that, as proposed by the Baas-Becking hypothesis, 'the environment selects' and is, in part, responsible for spatial variation in microbial diversity. However, recent studies also dispute the idea that 'everything is everywhere'. We also consider how the processes that generate and maintain biogeographic patterns in macroorganisms could operate in the microbial world.
The distribution of microorganisms, and especially pathogens, over airborne particles of different sizes has been ignored to a large extent, but it could have significant implications regarding the dispersion of these microorganisms across the planet, thus affecting human health.
We examined the microbial quality of the aerosols over the eastern Mediterranean region during an African storm to determine the size distribution of microorganisms in the air.
We used a five-stage cascade impactor for bioaerosol collection in a coastal city on the eastern Mediterranean Sea during a north African dust storm. Bacterial communities associated with aerosol particles of six different size ranges were characterized following molecular culture-independent methods, regardless of the cell culturability (analysis of 16S rRNA genes).
All 16S rDNA clone libraries were diverse, including sequences commonly found in soil and marine ecosystems. Spore-forming bacteria such as Firmicutes dominated large particle sizes (> 3.3 microm), whereas clones affiliated with Actinobacteria (found commonly in soil) and Bacteroidetes (widely distributed in the environment) gradually increased their abundance in aerosol particles of reduced size (< 3.3 microm). A large portion of the clones detected at respiratory particle sizes (< 3.3 microm) were phylogenetic neighbors to human pathogens that have been linked to several diseases.
The presence of aerosolized bacteria in small size particles may have significant implications to human health via intercontinental transportation of pathogens.
The finding that total viral abundance is higher than total prokaryotic abundance and that a significant fraction of the prokaryotic community is infected with phages in aquatic systems has stimulated research on the ecology of prokaryotic viruses and their role in ecosystems. This review treats the ecology of prokaryotic viruses (phages') in marine, freshwater and soil systems from a,virus point of view'. The abundance of viruses varies strongly in different environments and is related to bacterial abundance or activity suggesting that the majority of the viruses found in the environment are typically phages. Data on phage diversity are sparse but indicate that phages are extremely diverse in natural systems. Lytic phages are predators of prokaryotes, whereas lysogenic and chronic infections represent a parasitic interaction. Some forms of lysogeny might be described best as mutualism. The little existing ecological data on phage populations indicate a large variety of environmental niches and survival strategies. The host cell is the main resource for phages and the resource quality, i.e., the metabolic state of the host cell, is a critical factor in all steps of the phage life cycle. Virus-induced mortality of prokaryotes varies strongly on a temporal and spatial scale and shows that phages can be important predators of bacterioplankton. This mortality and the release of cell lysis products into the environment can strongly influence microbial food web processes and biogeochemical cycles. Phages can also affect host diversity, e.g., by `killing the winner' and keeping in check competitively dominant species or populations. Moreover, they mediate gene transfer between prokaryotes, but this remains largely unknown in the environment. Genomics or proteomics are providing us now with powerful tools in phage ecology, but final testing will have to be performed in the environment.
Dissolved organic polymers released by phytoplankton and bacteria abiologically self-assemble in surface ocean waters into nano-to micro-sized gels containing polysaccharides, proteins, lipids and other components. These gels concentrate in the sea surface microlayer (SML), where they can potentially contribute to sea spray aerosol (SSA). Sea spray is a major source of atmospheric aerosol mass over much of the earth’s surface, and knowledge of its properties (including the amount and nature of the organic content), size distributions and fluxes are fundamental for determining its role in atmospheric chemistry and climate. Using a cascade impactor, we collected size-fractionated aerosol particles from ambient air and from freshly generated Sea Sweep SSA in the western North Atlantic Ocean together with biological and chemical characterization of subsurface and SML waters. Spectrophotometric methods were applied to quantify the polysaccharide-containing transparent exopolymer (TEP) and protein-containing Coomassie stainable material (CSM) in these particles and waters. This study demonstrates that both TEP and CSM in surface ocean waters are aerosolized with sea spray with the greatest total TEP associated with particles <180 nm in diameter and >5 000 nm. The higher concentrations of TEP and CSM in particles >5 000 nm most likely reflects collection of microorganism cells and/or fragments. The greater concentration of CSM in larger size particles may also reflect greater stability of proteinaceous gels compared to polysaccharide-rich gels in surface waters and the SML. Both TEP and CSM were measured in the ambient marine air sample with concentrations of 2.1 ± 0.16 μg Xanthan Gum equivalents (XG eq.) m−3 and 14 ± 1.0 μg bovine serum albumin equivalents (BSA eq.) m−3. TEP in Sea Sweep SSA averaged 4.7 ± 3.1 μg XG eq. m−3 and CSM 8.6 ± 7.3 μg BSA eq. m−3. This work shows the transport of marine biogenic material across the air-sea interface through primary particle emission and the first demonstration of particle size discriminated TEP and CSM characterization of SSA and ambient aerosol under field conditions.
The input of soluble iron in dust delivered to the ocean and lakes is critical to their biogeochemistry and phytoplankton productivity. Most iron in soils and sediment deposits is insoluble, while only a tiny fraction is soluble and therefore suitable to meet the phytoplankton's requirements for photosynthesis and nitrogen assimilation. Aerosol deposition constitutes a major source of soluble iron to oceans and lakes, and in some regions the low phytoplankton productivity has been related to limitations in the supply of soluble iron from terrestrial sources. It is suggested that during atmospheric transport part of the insoluble iron is converted into soluble form. While the understanding of increased bioavailability of iron during atmospheric transport is improving, there are only a limited number of studies that actually quantify the increase in iron bioavailability in dust. In this study we compare the soluble ferrous iron, Fe (II) content in dust collected at deposition sites in the high altitude mountains of the Sierra Nevada, Spain, to the source of dust in North Africa. We found that the dust is greatly enriched (on average 15 times) in Fe (II) relative to the fine fraction (<45-µm) of the parent soil collected from North African dust sources.
We quantified dry and wet deposition of dust, nitrogen, and phosphorus over the southwest Mediterranean region (Sierra Nevada, Spain) and assessed its effects on the nutrient status and the chlorophyll a (Chl a) concentration in two high mountain lakes, Atmospheric deposition of particulate matter (PM) and total phosphorus (TP) were mainly associated with dryfall and showed a seasonal pattern similar to that reported for Saharan dust export toward the Mediterranean region, with maxima during spring and summer. In contrast, total nitrogen (TN) deposition was related to rainfall and did not follow the pattern observed for PM and TP. The molar TN: TP ratio was significantly lower (i.e., phosphorus-enriched) in dry deposition (TN vs. TP slope = 11.2) than in wet deposition (TN vs. TP slope = 95.5). In the study lakes, the molar TN: TP ratios and the Chl a concentrations were significantly influenced by the molar TN: TP ratio and the TP content of atmospheric deposition, respectively. Lake responses were more pronounced in the more phosphorous-limited system. These results establish a direct connection between atmospheric deposition and lake nutrient status and Chl a, making evident that in the Mediterranean region these inputs are an important source of phosphorous affecting biogeochemistry of oligotrophic systems.
A novel methodology was used to evaluate the contribution of Saharan dust to the atmospheric deposition of particulate material (PM), total phosphorus (TP), and total nitrogen (TN) in the south-eastern Iberian Peninsula. Dry and wet aerosol depositions were measured weekly during two one-year periods at one site and simultaneously during spring-summer of the same years at two other sites (inter-site distance of ~ 40 km). Statistical relationships among depositions at the different sites permitted differentiation of Saharan dust inputs from locally derived dust. PM and TP depositions were synchronous among the three study sites; the synchrony was elevated during periods of Saharan intrusions (evaluated by air mass retro-trajectories analyses), but no temporal correlation was observed during periods without Saharan intrusions. According to ANOVA results, PM and TP depositions were both significantly affected by Saharan intrusions. During weeks with Saharan intrusions, PM deposition increased around 85% above background levels, with no differences among the three sites, while TP deposition increased by 1.1 µmol TP m-2 d-1, i.e., 29% to 81% above background levels depending on the site. There were no correlations or differences in TN deposition among sites or as a function of Saharan intrusion periods. The annual contribution of PM and TP from Saharan dust was 75 kg ha-1 and 0.07 kg P ha-1, respectively, which can be considered a genuine input for the ecosystems in this area. This novel approach is likely to be valid in any area in the world under atmospheric deposition of long-range transported material.
HYSPLIT, developed by NOAA’s Air Resources Laboratory, is one of the most widely used models for atmospheric trajectory and dispersion calculations. We present the model’s historical evolution over the last 30 years from simple hand drawn back trajectories to very sophisticated computations of transport, mixing, chemical transformation, and deposition of pollutants and hazardous materials. We highlight recent applications of the HYSPLIT modeling system, including the simulation of atmospheric tracer release experiments, radionuclides, smoke originated from wild fires, volcanic ash, mercury, and wind-blown dust.
The diversity of airborne microorganisms that potentially reach aquatic ecosystems during rain events is poorly explored. Here, we used a culture independent approach to characterize bacterial assemblages during rain events with and without Saharan dust influence arriving to a high mountain lake in the Austrian Alps. Bacterial assemblage composition differed significantly between samples with and without Saharan dust influence. Though alpha diversity indices were within the same range in both sample categories, rain events with Atlantic or continental origins were dominated by Betaproteobacteria, whereas those with Saharan dust intrusions were dominated by Gammaproteobacteria. The high diversity and evenness observed in all samples suggests that different sources of bacteria contributed to the airborne assemblage collected at the lake shore. During experiments with bacterial assemblages collected during rain events with Saharan dust influence, cell numbers rapidly increased in sterile lake water from initially ∼ 3×103 cell ml-1 to 3.6 – 11.1×105 cells ml-1 within 4 to 5 days and initially rare taxa dominated at the end of the experiment. Our study documents the dispersal of viable bacteria associated to Saharan dust intrusions traveling northwards as far as 47° latitude.
We assessed the effects of Saharan dust inputs of particulate matter (PM), total phosphorus (TP), total nitrogen, and water soluble organic carbon (WSOC) on bacterial abundance (BA) in two alpine lakes and two reservoirs in the Mediterranean region. We also experimentally assessed the effects of dust inputs on bacterial activity and community composition and explored the presence of airborne bacteria. We found synchronous BA dynamics at least in one of the study years for each corresponding pair of ecosystems, suggesting an external control. The link between BA dynamics and inputs of PM, WSOC, or TP occurred only in those ecosystems with severe P-limitation and low dissolved organic carbon. The response was most intense in the most P-limited ecosystem. Dust addition had a significant positive effect on bacterial growth and abundance, but not on richness, diversity, or composition of the indigenous bacterial assemblages. We also obtained experimental evidence that some airborne bacteria could develop in oligotrophic waters by observing the growth of gamma-proteobacteria, a group poorly represented in natural aquatic environments.
In this work, we have compared two methods for the determination of water-soluble organic carbon (WSOC) in ambient aerosols, one based on a total organic carbon analyzer (TOC) and the other based on an aerosol carbon analyzer (ACA). The two instruments entail different pre-analysis treatment of aerosol water extracts. Standard compounds spiked onto filters showed satisfactory recovery ranging from 75% to 105% by the two methods, demonstrating that the extraction procedures and subsequent pre-analysis pre-treatment are quantitative in both methods. Measurements of standard compounds and aerosol samples show that the two methods give equivalent results by paired t-test. The TOC method offers a limit of detection (LOD) of 2.6μg/sample, whereas the ACA method gives a LOD of 4.8μg/sample. Acid treatment to remove carbonate carbon was found unnecessary for the determination of WSOC in PM2.5 aerosols. Although the sample treatment procedures and the detection limits of these two methods are different to some extent, both are suitable for the determination of WSOC in aerosol samples. The TOC method has the advantages of requiring less time in sample pre-treatment and offering slightly lower detection limit. The TOC instruments also have the additional advantage of automated sample analysis while the ACA instruments require manual operation.
We studied if the presence of Saharan dust intrusions and the rains modify the chemical signature of the wet and dry deposition in the southern Iberian Peninsula. We have sorted the 109 sampling weeks by the presence (rainy weeks) or absence (dry weeks) of rain and by the occurrence or not of Saharan dust intrusions. Dry deposition dominated the delivery of particulate material (PM), total phosphorus (TP), soluble reactive phosphorus (SRP), Ca2+, Mg2+ and K+, whereas wet deposition dominated the delivery of Na+, total nitrogen, NO-3 and SO-4. In the dry weeks, the presence of Saharan dust intrusions lead to higher inputs of PM, TP, SRP, Ca2+, Mg2+ and K+ in the dry deposition. Conversely, in the rainy weeks, there were no differences in mean values of dry deposition irrespective of the occurrence of Saharan dust intrusions. Nevertheless, in the presence of Saharan intrusions and some rain, the weekly collection of PM, TP and Ca2+ in dry deposition were significantly higher and increased as rainfall was lower. By contrast, the ions Cl- and Na+ in wet deposition were higher in absence of Saharan dust intrusion and increased as rainfall increased.
The composition and prevalence of microorganisms in the middle-to-upper troposphere (8-15 km altitude) and their role in aerosol-cloud-precipitation interactions represent important, unresolved questions for biological and atmospheric science. In particular, airborne microorganisms above the oceans remain essentially uncharacterized, as most work to date is restricted to samples taken near the Earth's surface. Here we report on the microbiome of low- and high-altitude air masses sampled onboard the National Aeronautics and Space Administration DC-8 platform during the 2010 Genesis and Rapid Intensification Processes campaign in the Caribbean Sea. The samples were collected in cloudy and cloud-free air masses before, during, and after two major tropical hurricanes, Earl and Karl. Quantitative PCR and microscopy revealed that viable bacterial cells represented on average around 20% of the total particles in the 0.25- to 1-μm diameter range and were at least an order of magnitude more abundant than fungal cells, suggesting that bacteria represent an important and underestimated fraction of micrometer-sized atmospheric aerosols. The samples from the two hurricanes were characterized by significantly different bacterial communities, revealing that hurricanes aerosolize a large amount of new cells. Nonetheless, 17 bacterial taxa, including taxa that are known to use C1-C4 carbon compounds present in the atmosphere, were found in all samples, indicating that these organisms possess traits that allow survival in the troposphere. The findings presented here suggest that the microbiome is a dynamic and underappreciated aspect of the upper troposphere with potentially important impacts on the hydrological cycle, clouds, and climate.
We quantified dry and wet deposition of dust, nitrogen, and phosphorus over the southwest Mediterranean region (Sierra Nevada, Spain) and assessed its effects on the nutrient status and the chlorophyll a (Chl a) concentration in two high mountain lakes, Atmospheric deposition of particulate matter (PM) and total phosphorus (TP) were mainly associated with dryfall and showed a seasonal pattern similar to that reported for Saharan dust export toward the Mediterranean region, with maxima during spring and summer. In contrast, total nitrogen (TN) deposition was related to rainfall and did not follow the pattern observed for PM and TP. The molar TN: TP ratio was significantly lower (i.e., phosphorus-enriched) in dry deposition (TN vs. TP slope = 11.2) than in wet deposition (TN vs. TP slope = 95.5). In the study lakes, the molar TN: TP ratios and the Chl a concentrations were significantly influenced by the molar TN: TP ratio and the TP content of atmospheric deposition, respectively. Lake responses were more pronounced in the more phosphorous-limited system. These results establish a direct connection between atmospheric deposition and lake nutrient status and Chl a, making evident that in the Mediterranean region these inputs are an important source of phosphorous affecting biogeochemistry of oligotrophic systems.
1] Organic aerosols are important light-absorbing compounds in the atmosphere that influence climate by filtering solar radiation and interact with the biosphere via deposition to aquatic and terrestrial ecosystems. There is a limited understanding of their chemical properties and even less is known about the relationships between fluorescent properties and widely used optical properties of aerosols in the vertical air column, such as aerosol optical depth (d Al), aerosol size distribution, and single scattering albedo (w 0Al). In this study, we examined relationships between spectroscopic (fluorescence and absorbance) properties of the water-soluble organic compounds (WSOC) in aerosol deposition and ground-based remote sensing measurements of aerosols in the atmospheric column. With both techniques, we found important differences between Saharan-and marine-dominated organic aerosols. Saharan-dominated WSOC had more intense fluorescence and higher content of reduced quinone-like fluorescent components than marine-dominated WSOC, and amino acid-like fluorescence was substantial in both types of deposition. Both particulate matter loading and molar absorption in the UV range were significantly related to iron content and may reflect a contribution from iron to light absorption. Saharan-dominated aerosols generally had higher d Al and volume concentration of coarse mode particles (>0.5 mm; V c2) than marine-dominated aerosols. Using fluorescence spectroscopy and PARAFAC modeling, we found that reduced quinone-like compounds were significantly and positively related to d Al and V c2 . The relationships that emerged from this study provide a basis for relating WSOC and columnar measurements in the future. Citation: Mladenov, N., I. Reche, F. J. Olmo, H. Lyamani, and L. Alados-Arboledas (2010), Relationships between spectroscopic properties of high-altitude organic aerosols and Sun photometry from ground-based remote sensing,
Marine aerosols are formed primarily by the eruption of rising bubbles through the sea-surface microlayer (SML), and aerosol formation is the main vector for transport of bacteria and viruses across the air–sea interface. The processes by which materials are transported to and through the SML to the atmosphere results in an enrichment in the SML of microbial and other organisms. We evaluated concentrations of marine bacteria and viruses in natural aerosols and in those simulated by bubbling sea sprays and compared them to the concentrations in SML (200– thick) and in subsurface water. Association of microorganisms with transparent gel-like organic particles and physiological status of bacteria were also assessed. We found a 15–25-fold enrichment in bacteria and viruses during transport from subsurface waters to the SML, and then into the atmosphere. The majority of microorganisms in aerosols were found embedded in the organic particles. Large portions of microorganisms in the SML were also associated with the particles, while in subsurface waters most of them were free-living. A larger percentage of damaged and less active bacterial cells occur in the microlayer than in subsurface waters, and preliminary data suggest that an even greater percentage occurs in aerosols. Our data support the idea that the SML in a major source of microorganisms entering the atmosphere from water bodies. Aerosolization is potentially an important long-distance dispersal mechanism and may account for observed cosmopolitan distributions of some bacteria.
We have analysed the diversity of the bacteria, which grow after addition of concentrated airborne particles and desert dust in different microcosms combinations with water samples from oligotrophic alpine lakes. We used, on the one hand, airborne bacteria transported by an African dust plume and collected in a high mountain area in the central Pyrenees (Spain). On the other hand, we collected desert dust in Mauritania (c. 3000 km distance, and a few days estimated airborne journey), a known source region for dust storms in West Africa, which originates many of the dust plumes landing on Europe. In all the dust-amended treatments we consistently observed bacterial growth of common phyla usually found in freshwater ecosystems, i.e. Alpha-, Beta- and Gammaproteobacteria, Actinobacteria, and a few Bacteroidetes, but with different composition based on lake water pretreatment and dust type. Overall, we tentatively split the bacterial community in (i) typical freshwater non-airborne bacteria, (ii) cosmopolitan long-distance airborne bacteria, (iii) non-freshwater low-distance airborne bacteria, (iv) non-freshwater long-distance airborne soil bacteria and (v) freshwater non-soil airborne bacteria. We identified viable long-distance airborne bacteria as immigrants in alpine lakes (e.g. Sphingomonas-like) but also viable putative airborne pathogens with the potential to grow in remote alpine areas (Acinetobacter-like and Arthrobacter-like). Generation of atmospheric aerosols and remote dust deposition is a global process, largely enhanced by perturbations linked to the global change, and high mountain lakes are very convenient worldwide model systems for monitoring global-scale bacterial dispersion and pathogens entries in remote pristine environments.
The Bacteria and Archaea are the most genetically diverse superkingdoms of life, and techniques for exploring that diversity are only just becoming widespread. Taxonomists classify these organisms into species in much the same way as they classify eukaryotes, but differences in their biology-including horizontal gene transfer between distantly related taxa and variable rates of homologous recombination-mean that we still do not understand what a bacterial species is. This is not merely a semantic question; evolutionary theory should be able to explain why species exist at all levels of the tree of life, and we need to be able to define species for practical applications in industry, agriculture, and medicine. Recent studies have emphasized the need to combine genetic diversity and distinct ecology in an attempt to define species in a coherent and convincing fashion. The resulting data may help to discriminate among the many theories of prokaryotic species that have been produced to date.
Current theories of influenza viral epidemiology have not explained the persistence, seasonality, and explosive outbreaks
of virus over large geographic areas. It is postulated in this paper that atmospheric dispersion and intercontinental scale
transport of airborne aerosolized influenza virus may contribute to the spread, persistence, and ubiquity of the disease,
the explosiveness of epidemics, and the prompt region-wide occurrence of outbreaks and that seasonal changes in circulation
patterns and the dispersive character of the atmosphere may help to explain the regular annual cycle of influenza activity.
There are an estimated 10(31) viruses on Earth, most of which are phages that infect bacteria. Metagenomic analyses have shown that environmental viral communities are incredibly diverse. There are an estimated 5000 viral genotypes in 200 liters of seawater and possibly a million different viral genotypes in one kilogram of marine sediment. By contrast, some culturing and molecular studies have found that viruses move between different biomes. Together, these findings suggest that viral diversity could be high on a local scale but relatively limited globally. Also, by moving between environments, viruses can facilitate horizontal gene transfer.
Desert winds aerosolize several billion tons of soil-derived dust each year, including concentrated seasonal pulses from Africa and Asia. These transoceanic and transcontinental dust events inject a large pulse of microorganisms and pollen into the atmosphere and could therefore have a role in transporting pathogens or expanding the biogeographical range of some organisms by facilitating long-distance dispersal events. As we discuss here, whether such dispersal events are occurring is only now beginning to be investigated. Huge dust events create an atmospheric bridge over land and sea, and the microbiota contained within them could impact downwind ecosystems. Such dispersal is of interest because of the possible health effects of allergens and pathogens that might be carried with the dust.