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The association between bacteria and rain and possible resultant meteorological implications

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... Tableau I-1. Production d'alginate et la susceptibilité aux radicaux oxygène intermédiaires des souches de P. syringae dont la production de N-acyl homoserine lactone (AHL) est différente (Quiñones et al., 2005) Article en co-auteur (Amato et al., 2007a;Constantinidou et al., 1990;Sands et al., 1982), dans les rivières Morris et al., 2008), les plantes sauvages (Mohr et al., 2008;Morris et al., 2008) ou encore le manteau neigeux saisonnier . ...
... Plusieurs études ont mis en évidence des émissions de bactéries et de P. syringae dans l'atmosphère, ainsi que leurs variations diurnes et annuelles (Constantinidou et al., 1990;Hirano and Upper, 2000;Lighthart, 1999;Lindemann et al., 1982;Shaffer and Lighthart, 1997;Tong and Lighthart, 2000). La (Lighthart, 1999) Si plusieurs travaux avaient caractérisés P. syringae dans les aérosols, d'autres comme ceux de Sands et al. (1982) puis un peu plus tard Constantinidou et al. (1990), avaient mis en évidence sa déposition à travers la pluie. P. syringae étant connue pour ses propriétés glaçogènes depuis les travaux de Maki et al. (1974) et ceux de Vali et al. (1976). ...
... P. syringae étant connue pour ses propriétés glaçogènes depuis les travaux de Maki et al. (1974) et ceux de Vali et al. (1976). Ces observations avaient fait émerger l'idée d'une possible existence d'un cycle biologique par lequel la colonisation des plantes par des bactéries glaçogènes comme P. syringae, contribue à déclencher des processus atmosphériques essentiels pour la précipitation, qui à son tour favorise la croissance des végétaux des microorganismes (Sands et al., 1982). Il ne s'agissait plus de considérer le rôle de la pluie uniquement dans la dispersion locale des bactéries sur la plante avec les projections de gouttes de pluie, mais du transport par les nuages. ...
... W e have known for around 4 decades that soil, decaying vegetation, and plant surfaces harbor organic ice-nucleating particles (INP) and that their abundance and high temperature of activity suggest they are significant sources of atmospheric ice nuclei (1)(2)(3)(4)(5)(6)(7)(8). The focus of more recent research has been to elucidate their identities, reservoirs, and emissions to and role, if any (9), in the troposphere (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). ...
... They are particularly abundant on crops (7) but are also plentiful on many nonagricultural plants and in habitats such as freshwater and associated biofilms (7,15,30). Possession of ice nucleation activity may confer several advantages (11,30,31), including the ice nucleation of cloud drop-lets as an active deposition and dissemination mechanism (8,15,30,32). ...
... INA bacteria have been detected in air above crops under dry conditions and were enhanced ϳ30-fold during rainfall (33,34), and they were relatively abundant in air downwind of harvesting (35). They have also been isolated from cloud water (18,36,37), from ice and rain at up to 2,500 m above a wheat field (8), and from ϳ50% of rain and snow samples (15). A typically large reduction in INP active at ϾϪ12°C after heat treatment or cell wall digestion suggests their ubiquity in precipitation (38,39); rainfall itself stimulates the release of biological INP from vegetation and the soil surface (33,34,40,41). ...
... 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). ...
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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
... 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. ...
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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.
... Similarly, several ice-nucleation active bacteria have been reported [25][26][27][28] and isolated from clouds [29,30] and precipitation, including rainfall [9] and snowfall [9,31,32]. Thus, bacteria likely play a role and are involved in precipitation, which is generally referred to as "bioprecipitation" [33,34]. However, it is still controversial to what extent biological particles, including bacterial particles, contribute to nucleation and are involved in precipitation on a global scale [7,[35][36][37]. ...
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Background Bacteria emitted into the atmosphere eventually settle to the pedosphere via sedimentation (dry deposition) or precipitation (wet deposition), constituting a part of the global cycling of substances on Earth, including the water cycle. In this study, we aim to investigate the taxonomic compositions and flux densities of bacterial deposition, for which little is known regarding the relative contributions of each mode of atmospheric deposition, the taxonomic structures and memberships, and the aerodynamic properties in the atmosphere. Results Precipitation was found to dominate atmospheric bacterial deposition, contributing to 95% of the total flux density at our sampling site in Korea, while bacterial communities in precipitation were significantly different from those in sedimentation, in terms of both their structures and memberships. Large aerodynamic diameters of atmospheric bacteria were observed, with an annual mean of 8.84 μm, which appears to be related to their large sedimentation velocities, with an annual mean of 1.72 cm s − 1 for all bacterial taxa combined. The observed mean sedimentation velocity for atmospheric bacteria was larger than the previously reported mean sedimentation velocities for fungi and plants. Conclusions Large aerodynamic diameters of atmospheric bacteria, which are likely due to the aggregation and/or attachment to other larger particles, are thought to contribute to large sedimentation velocities, high efficiencies as cloud nuclei, and large amounts of precipitation of atmospheric bacteria. Moreover, the different microbiotas between precipitation and sedimentation might indicate specific bacterial involvement and/or selective bacterial growth in clouds. Overall, our findings add novel insight into how bacteria participate in atmospheric processes and material circulations, including hydrological circulation, on Earth.
... The properties of certain bioaerosols may allow them to affect meteorological processes by acting as cloud condensation or ice nuclei, thereby influencing cloud cover, precipitation formation, and the Earth's energy budget (e.g. [9][10][11][12]). Despite the varied roles of bioaerosols in environmental health, biological dispersion, and the land-atmosphere system, their ecological sources and emission mechanisms remain poorly understood [13]. ...
Article
The environmental sources of microbial aerosols and processes by which they are emitted into the atmosphere are not well characterized. In this study we analyzed microbial cells and biological ice nucleating particles (INPs) in smoke emitted from eight prescribed wildland fires in North Florida. When compared to air sampled prior to ignition, samples of the air-smoke mixtures contained fivefold higher concentrations of microbial cells (6.7 ± 1.3 × 104 cells m-3) and biological INPs (2.4 ± 0.91 × 103 INPs m-3 active at temperatures ≥ -15 °C), and these data significantly positively correlated with PM10. Various bacteria could be cultured from the smoke samples, and the nearest neighbors of many of the isolates are plant epi- and endophytes, suggesting vegetation was a source. Controlled laboratory combustion experiments indicated that smoke emitted from dead vegetation contained significantly higher numbers of cells, INPs, and culturable bacteria relative to the green shrubs tested. Microbial viability of smoke aerosols based on formazan production and epifluorescent microscopy revealed no significant difference in the viable fraction (~80%) when compared to samples of ambient air. From these data, we estimate each fire aerosolized an average of 7 ± 4 × 109 cells and 2 ± 1 × 108 biological INPs per m2 burned and conclude that emissions from wildland fire are sources of viable microbial aerosols to the atmosphere.
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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
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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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Ice nucleating particles (INPs) are a rare subset of aerosol particles that initiate cloud droplet freezing at temperatures above the homogenous freezing point of water (−38 °C). Considering that the ocean covers 70 % of the earth's surface and represent a large potential source of INPs, it is imperative that the uncertainties in the identities and emissions of ocean INP become better understood. However, the specific underlying drivers of marine INP emissions and their identities remain largely unknown due to limited observations and the challenge involved in isolating exceptionally rare IN forming particles. By generating nascent sea spray aerosol (SSA) over a range of biological conditions, mesocosm studies show that microbes can contribute to marine INPs. Here, we identify 14 (30 %) cultivable halotolerant ice nucleating microbes and fungi among 47 total isolates recovered from precipitation and aerosol samples collected in coastal air in Southern California. IN isolates collected in coastal air were found to nucleate ice from extremely warm to moderate freezing temperatures (−2.3 to −18 °C). Air mass trajectory analyses, and cultivability in marine growth media indicate marine origins of these isolates. Further phylogenetic analysis confirmed that at least two of the 14 IN isolates were of marine origin. Moreover, results from cell washing experiments demonstrate that most IN isolates maintained freezing activity in the absence of nutrients and cell growth media. This study provides confirmation of previous studies' findings that implicated microbes as a potential source of marine INPs and additionally demonstrates links between precipitation, marine aerosol and IN microbes.
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Biological particles in the Earth's atmosphere are a distinctive category of ice nucleating particles (INPs) due to their capability of facilitating ice crystal formation in clouds at relatively warm temperatures. Field observations and model simulations have shown that biological INPs affect cloud and precipitation formation and regulate regional or even global climate, although there are considerable uncertainties in modeling and large gaps between observed and model simulated contribution of biological particles to atmospheric INPs. This paper overviews the latest researches about biological INPs in the atmosphere. Firstly, we describe the primary ice nucleation mechanisms, and measurements and model simulations of atmospheric biological INPs. Secondly, we summarize the ice nucleating properties of biological INPs from diverse sources such as soils or dust, vegetation (e.g., leaves and pollen grains), sea spray, and fresh waters, and controlling factors of biological INPs in the atmosphere. Then we review the abundance and distribution of atmospheric biological INPs in diverse ecosystems. Finally, we discuss the open questions in further studies on atmospheric biological INPs, including the requirements for developing novel detection techniques and simulation models, as well as the comprehensive investigation of characteristics and influencing factors of atmospheric biological INPs.
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