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The association between bacteria and rain and possible resultant meteorological implications
... While the classifier used in this study was not trained on Fusarium, there is no apparent reason why this should not be possible with appropriate training data to investigate Fusarium emissions. It has previously been shown that even a modest primary ice concentration of 0.01 L −1 may lead to rapid supercooled cloud glaciation via secondary ice processes, leading to enhanced precipitation, where BioPM may contribute to the source of primary ice nucleating particles necessary to initiate this process [20]; this builds the narrative of the bioprecipitation hypothesis [23,24], where it has been speculated that rainfall-induced enhancement of iceactive BioPM yields an environment beneficial for the growth of plants and microorganisms via enhanced precipitation caused by bio-IN driven cloud glaciation, creating feedback where enhancement in rainfall creates an enhancement in bio-IN emissions. Widescale high time-resolution BioPM monitoring will be necessary to investigate this hypothesis via big data approaches due to the likely meso-to synoptic scale nature of the feedback, again showcasing the impacts and utility of the methods employed in this study to tackle big questions pertaining to BioPM impacts. ...
Biological particulate matter (BioPM) is a poorly constrained, ubiquitous, and diverse subset of atmospheric aerosols. They influence climate, air quality, and health via many mechanisms, spurring renewed interest in constraining their emissions to elucidate their impacts. In order to build the framework required to assess the role of BioPM in these multidisciplinary areas, it is necessary to develop robust, high time-resolution detection methodologies so that BioPM emissions can be understood and characterized. In this study, we present ambient results from intensive monitoring at UK peri-urban and coastal ground sites using high time-resolution real-time bioaerosol spectrometers. We demonstrate the utility of a new dimensional reduction-driven BioPM classification scheme, where laboratory sample training data collected at the ChAMBRe facility were used to generate broad taxonomic class time series data of key species of interest. We show the general trends of these representative classes, spanning spring, early summer, and autumn periods between 2019 and 2021. Diurnal behaviors and meteorological relationships were investigated and contextualized; a key result arising from this study was the demonstration of rainfall-induced enhancement of nighttime Penicillium-like aerosol, where rainfall crucially only acts to enhance the quantity emitted without significantly influencing the early morning timing of peak spore liberation.
... The release of bioaerosols, which can serve as cloud condensation nuclei (CCN) or ice nuclei (IN), can in turn influence the evolution of clouds and precipitation, thus closing a feedback cycle known as bioprecipitation (Sands et al., 1982;Möhler et al., 2007;Morris et al., 2014;Steiner et al., 2015;Fröhlich-Nowoisky et al., 2016). Especially over vegetated regions, in marine environments, or under remote conditions, bioparticles might represent a significant fraction of CCN and IN (Andreae and Rosenfeld, 2008;Pöschl et al., 2010;Pöhlker et al., 2012;Burrows et al., 2013;Wilson et al., 2015). ...
Certain biological particles are highly efficient ice nuclei (IN), but the actual contribution of bioparticles to the pool of atmospheric IN and their relation to precipitation are not well characterized. We investigated the composition of bioaerosols, ice nucleation activity, and the effect of rainfall by metagenomic sequencing and freezing experiments of aerosol samples collected during the INUIT 2016 campaign in a rural dryland on the eastern Mediterranean island of Cyprus. Taxonomic analysis showed community changes related to rainfall. For the rain-affected samples, we found higher read proportions of fungi, particularly of Agaricomycetes, which are a class of fungi that actively discharge their spores into the atmosphere in response to humidity changes. In contrast, the read proportions of bacteria were reduced, indicating an effective removal of bacteria by precipitation. Freezing experiments showed that the IN population in the investigated samples was influenced by both rainfall and dust events. For example, filtration and heat treatment of the samples collected during and immediately after rainfall yielded enhanced fractions of heat-sensitive IN in the size ranges larger than 5 µm and smaller than 0.1 µm, which were likely of biological origin (entire bioparticles and soluble macromolecular bio-IN). In contrast, samples collected in periods with dust events were dominated by heat-resistant IN active at lower temperatures, most likely mineral dust. The DNA analysis revealed low numbers of reads related to microorganisms that are known to be IN-active. This may reflect unknown sources of atmospheric bio-IN as well as the presence of cell-free IN macromolecules that do not contain DNA, in particular for sizes < 0.1 µm. The observed effects of rainfall on the composition of atmospheric bioaerosols and IN may influence the hydrological cycle (bioprecipitation cycle) as well as the health effects of air particulate matter (pathogens, allergens).
... However, the discovery of bacterial ice nucleation led scientists to speculate about the potential involvement of ice nucleation active microorganisms in atmospheric processes. Sands and colleagues proposed a "bioprecipitation" cycle, where crops harboring large populations of ice nucleation active bacteria serve as sources of aerial bacterial ice nuclei involved in the formation of precipitation in clouds, which enhances plant growth and crops, enabling in turn the development of new epiphytic bacterial populations acting as ice nuclei in the atmosphere [11,12]. The actual significance of bioprecipitation in nature is under increasing investigation. ...
The formation of precipitation in clouds is initiated by inorganic and organic/biological ice nuclei. Certain species of bacteria and fungi are known to act as efficient biological ice nuclei at temperatures between −10 and 0 • C. Biological ice nuclei have been found and characterized in precipitation samples (snow, rain, and hail). We investigated the presence of warm temperature biological ice nuclei in 17 fresh snow samples from Greece and isolated and partially characterized ice nucleation active bacteria from these. All snow samples contained particles or other material active as ice nuclei at −9 • C in concentrations ranging from 3 to 943 nuclei/L. The numbers of this class of ice nuclei were reduced or eliminated after incubating snowmelt concentrates at 100 • C for 15 min and by treatment with lysozyme, a bacterial cell wall-degrading enzyme. These findings indicate the presence of microbial ice nuclei in snow samples from Greece. We also isolated ice nucleation active bacteria from some of the samples. These bacteria belong to genus Pseudomonas and are common on plants and soil. This is the first report on biological ice nuclei in precipitation samples from Greece.
Ice-nucleating particles (INPs) play a key role in ice formation and cloud microphysics and thus significantly impact the water cycle and the climate. However, our understanding of atmospheric INPs, particularly their sources, emissions, and spatiotemporal variability, is incomplete. While the enhancement of atmospheric INP concentrations with rainfall has been previously shown, a mechanistic understanding of the process is lacking. Here, we link detailed precipitation observations with near-surface atmospheric INP concentrations at a semi-arid grassland site in Colorado. Considering the during-precipitation air samples, INP concentrations positively correlate with cumulative rainfall kinetic energy and amount, suggesting that INP aerosolization is induced by raindrop and hailstone impact. By additionally analyzing the INP content of precipitation water, terrestrial source samples, and heat-treated samples, we demonstrate that local plants are the most important source of precipitation-induced INPs. Should INPs aerosolized by precipitation rise to cloud height, they could influence cloud ice fraction and initiate precipitation resulting in an aerosol-cloud-precipitation feedback.
Bioaerosols influence the climate processes, human health and overall ecosystem. Their type, concentration and diversity have important implications on various atmospheric processes however the limited understanding of bioaerosols-cloud-climate connection has resulted in existing uncertainty in climate models. Bioaerosols as ice nucleating particles (INPs) and cloud condensation nuclei (CCN) govern precipitation initiation, cloud formation and thus the complex hydrological cycle. Homogeneous nucleation takes place at colder temperatures (< − 38 ℃), while owing to their unique properties, certain ice nucleating bioaerosols can initiate freezing at much warmer temperatures (≧ − 10 °C) and thus are important for precipitation initiation through heterogenous nucleation mechanism. Flux of bioaerosols from diverse terrestrial and marine sources lead to their build-up in the atmosphere but rare bioaerosols act as CCN and INP. These rare characteristics of bioaerosols remain largely unexplored and need further attention and research. This work presents fundamental insights on the role of bioaerosols in cloud formation and ice nucleation mechanism along with an overview on the types, diversity and sources of bioaerosols. Most studies reviewed here on bioaerosol-cloud-climate connections are restricted to from specific research groups. Bioaerosol research is still in evolving stage and limited usage of advanced techniques of sampling and characterization is noticed particularly in developing countries. Lack of even baseline database on bioaerosols has resulted in poor understanding of their implications. The discussion presented here on species level information of cloud forming and ice nucleating bioaerosols will help researchers in developing fundamental understanding on characteristics and implications of bioaerosols. Bioaerosol research is expensive and thus joint campaigns by researchers from interdisciplinary areas should be encouraged. Application of high-throughput sequencing allows rapid taxonomic identification and such modern molecular methods should be routinely used for understanding implications of bioaerosols on climate as well as human health.
Certain biological particles are highly efficient ice nuclei (IN), but the actual contribution of bioparticles to the pool of atmospheric IN and their relation to precipitation are not well characterized. We investigated the composition of bioaerosols, ice nucleation activity, and the effect of rainfall by metagenomic sequencing and freezing experiments of aerosol samples collected during the INUIT 2016 campaign in a rural dryland on the Eastern Mediterranean island Cyprus. Taxonomic analysis showed community changes related to rainfall. For the rain-affected samples, we found higher read proportions of fungi, in particular of Agaricomycetes, which are a class of fungi actively discharging their spores into the atmosphere in response to humidity changes. In contrast, the read proportions of bacteria were reduced, indicating an effective removal of bacteria by precipitation. Freezing experiments showed that the IN population in the investigated samples was influenced by both rainfall and dust events. For example, filtration and heat treatment of the samples collected during and immediately after rainfall yielded enhanced fractions of heat-sensitive IN in the size ranges larger than 5 μm and smaller than 0.1 μm, which were likely of biological origin (entire bioparticles and soluble macromolecular bio-IN). In contrast, samples collected in periods with dust events were dominated by heat-resistant IN active at lower temperatures, most likely mineral dust. The DNA analysis revealed low numbers of reads related to microorganisms that are known to be IN-active. This may reflect unknown sources of atmospheric bio-IN as well as the presence of cell-free IN macromolecules that do not contain DNA, in particular for sizes
Microbial toxins pose a significant threat to the natural environment and all forms of life on planet earth. These biological organisms, such as enzymes, viruses or fragments wreak havoc on the environment and pose a health risk. Toxicity from bioaerosols has a negative impact on human life, causing acute adverse reactions, various types of illnesses, and carcinogenic disorders, among other issues. Although various aspects of bioaerosols have been studied, such as identification, quantification, dispersion, and epidemiology, bioaerosol research is still in its infancy, particularly in terms of understanding anthropogenic behavior. Most of the studies identify the negative impact of bioaerosols, albeit epidemiological evidence remains equivocal. Further, the regulatory enactments and legislative mechanisms for bioaerosol surveillance have yet to be implemented ineffectively in both developed and developing countries. In this overview, we evaluate the pathways and challenges of bioaerosols, highlight gaps in bioaerosol epidemiology, and discuss the public health implications of exposure to complex ecosystems. We also provide an overview of the current state of bioaerosol research, including sampling and enumeration procedures, qualitative and quantitative modeling, global statutory policies, and potential future approaches to addressing the challenges.
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