Articles | Volume 22, issue 1
https://doi.org/10.5194/bg-22-243-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-22-243-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Ideas and perspectives
| 
13 Jan 2025
Ideas and perspectives |
| 13 Jan 2025
| 13 Jan 2025
Ideas and perspectives: Microorganisms in the air through the lenses of atmospheric chemistry and microphysics
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
Pierre Amato
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
Laboratoire Microorganismes: Génome et Environnement (LMGE), Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
Kifle Aregahegn
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
now at: Department of Chemistry, York University, Toronto, ON, Canada
Muriel Joly
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
Amina Khaled
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
Tiphaine Labed-Veydert
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
Frédéric Mathonat
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
Leslie Nuñez López
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
Raphaëlle Péguilhan
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
now at: Department of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
Minghui Zhang
Institute of Chemistry Clermont-Ferrand, Université Clermont Auvergne, CNRS, 63000 Clermont-Ferrand, France
now at: Minerva Research Group, Max Planck Institute for Chemistry, 55128 Mainz, Germany
Related authors
Frédéric Mathonat, François Enault, Raphaëlle Péguilhan, Muriel Joly, Mariline Théveniot, Jean-Luc Baray, Barbara Ervens, and Pierre Amato
EGUsphere, https://doi.org/10.5194/egusphere-2025-3534, https://doi.org/10.5194/egusphere-2025-3534, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
Short summary
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The atmosphere plays key roles in Earth’s biogeochemical cycles. Airborne microbes were demonstrated previously to participate in the processing of organic carbon in clouds. Using a combinaison of complementary methods, we examined here, for the first time, their potential contribution to the pool of nitrogen compounds. Airborne microorganisms interact with abundant forms of nitrogen in the air and cloud and we provide global estimates.
Raphaëlle Péguilhan, Florent Rossi, Muriel Joly, Engy Nasr, Bérénice Batut, François Enault, Barbara Ervens, and Pierre Amato
Biogeosciences, 22, 1257–1275, https://doi.org/10.5194/bg-22-1257-2025, https://doi.org/10.5194/bg-22-1257-2025, 2025
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Using comparative metagenomics and metatranscriptomics, we examined the functioning of airborne microorganisms in clouds and a clear atmosphere. Clouds are atmospheric masses where multiple microbial processes are promoted compared with a clear atmosphere. Overrepresented microbial functions of interest include the processing of chemical compounds, biomass production, and regulation of oxidants. This has implications for biogeochemical cycles and microbial ecology.
Barbara Ervens, Ken S. Carslaw, Thomas Koop, and Ulrich Pöschl
EGUsphere, https://doi.org/10.5194/egusphere-2025-419, https://doi.org/10.5194/egusphere-2025-419, 2025
Short summary
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Over the past two decades, the European Geosciences Union (EGU) has demonstrated the success, viability and benefits of interactive open access (OA) publishing with public peer review in its journals, its publishing platform EGUsphere and virtual compilations. The article summarizes the evolution of the EGU/Copernicus publications and of OA publishing with interactive public peer review at large by placing the EGU/Copernicus publications in the context of current and future global open science.
Barbara Ervens, Andrew Rickard, Bernard Aumont, William P. L. Carter, Max McGillen, Abdelwahid Mellouki, John Orlando, Bénédicte Picquet-Varrault, Paul Seakins, William R. Stockwell, Luc Vereecken, and Timothy J. Wallington
Atmos. Chem. Phys., 24, 13317–13339, https://doi.org/10.5194/acp-24-13317-2024, https://doi.org/10.5194/acp-24-13317-2024, 2024
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Chemical mechanisms describe the chemical processes in atmospheric models that are used to describe the changes in the atmospheric composition. Therefore, accurate chemical mechanisms are necessary to predict the evolution of air pollution and climate change. The article describes all steps that are needed to build chemical mechanisms and discusses the advances and needs of experimental and theoretical research activities needed to build reliable chemical mechanisms.
Leslie Nuñez López, Pierre Amato, and Barbara Ervens
Atmos. Chem. Phys., 24, 5181–5198, https://doi.org/10.5194/acp-24-5181-2024, https://doi.org/10.5194/acp-24-5181-2024, 2024
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Living bacteria comprise a small particle fraction in the atmosphere. Our model study shows that atmospheric bacteria in clouds may efficiently biodegrade formic and acetic acids that affect the acidity of rain. We conclude that current atmospheric models underestimate losses of these acids as they only consider chemical processes. We suggest that biodegradation can affect atmospheric concentration not only of formic and acetic acids but also of other volatile, moderately soluble organics.
Amina Khaled, Minghui Zhang, and Barbara Ervens
Atmos. Chem. Phys., 22, 1989–2009, https://doi.org/10.5194/acp-22-1989-2022, https://doi.org/10.5194/acp-22-1989-2022, 2022
Short summary
Short summary
Chemical reactions with iron in clouds and aerosol form and cycle reactive oxygen species (ROS). Previous model studies assumed that all cloud droplets (particles) contain iron, while single-particle analyses showed otherwise. By means of a model, we explore the bias in predicted ROS budgets by distributing a given iron mass to either all or only a few droplets (particles). Implications for oxidation potential, radical loss and iron oxidation state are discussed.
Ramon Campos Braga, Barbara Ervens, Daniel Rosenfeld, Meinrat O. Andreae, Jan-David Förster, Daniel Fütterer, Lianet Hernández Pardo, Bruna A. Holanda, Tina Jurkat-Witschas, Ovid O. Krüger, Oliver Lauer, Luiz A. T. Machado, Christopher Pöhlker, Daniel Sauer, Christiane Voigt, Adrian Walser, Manfred Wendisch, Ulrich Pöschl, and Mira L. Pöhlker
Atmos. Chem. Phys., 21, 17513–17528, https://doi.org/10.5194/acp-21-17513-2021, https://doi.org/10.5194/acp-21-17513-2021, 2021
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Interactions of aerosol particles with clouds represent a large uncertainty in estimates of climate change. Properties of aerosol particles control their ability to act as cloud condensation nuclei. Using aerosol measurements in the Amazon, we performed model studies to compare predicted and measured cloud droplet number concentrations at cloud bases. Our results confirm previous estimates of particle hygroscopicity in this region.
Ramon Campos Braga, Daniel Rosenfeld, Ovid O. Krüger, Barbara Ervens, Bruna A. Holanda, Manfred Wendisch, Trismono Krisna, Ulrich Pöschl, Meinrat O. Andreae, Christiane Voigt, and Mira L. Pöhlker
Atmos. Chem. Phys., 21, 14079–14088, https://doi.org/10.5194/acp-21-14079-2021, https://doi.org/10.5194/acp-21-14079-2021, 2021
Short summary
Short summary
Quantifying the precipitation within clouds is crucial for our understanding of the Earth's hydrological cycle. Using in situ measurements of cloud and rain properties over the Amazon Basin and Atlantic Ocean, we show here a linear relationship between the effective radius (re) and precipitation water content near the tops of convective clouds for different pollution states and temperature levels. Our results emphasize the role of re to determine both initiation and amount of precipitation.
Mira L. Pöhlker, Minghui Zhang, Ramon Campos Braga, Ovid O. Krüger, Ulrich Pöschl, and Barbara Ervens
Atmos. Chem. Phys., 21, 11723–11740, https://doi.org/10.5194/acp-21-11723-2021, https://doi.org/10.5194/acp-21-11723-2021, 2021
Short summary
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Clouds cool our atmosphere. The role of small aerosol particles in affecting them represents one of the largest uncertainties in current estimates of climate change. Traditionally it is assumed that cloud droplets only form particles of diameters ~ 100 nm (
accumulation mode). Previous studies suggest that this can also occur in smaller particles (
Aitken mode). Our study provides a general framework to estimate under which aerosol and cloud conditions Aitken mode particles affect clouds.
Minghui Zhang, Amina Khaled, Pierre Amato, Anne-Marie Delort, and Barbara Ervens
Atmos. Chem. Phys., 21, 3699–3724, https://doi.org/10.5194/acp-21-3699-2021, https://doi.org/10.5194/acp-21-3699-2021, 2021
Short summary
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Although primary biological aerosol particles (PBAPs, bioaerosols) represent a small fraction of total atmospheric aerosol burden, they might affect climate and public health. We summarize which PBAP properties are important to affect their inclusion in clouds and interaction with light and might also affect their residence time and transport in the atmosphere. Our study highlights that not only chemical and physical but also biological processes can modify these physicochemical properties.
Amina Khaled, Minghui Zhang, Pierre Amato, Anne-Marie Delort, and Barbara Ervens
Atmos. Chem. Phys., 21, 3123–3141, https://doi.org/10.5194/acp-21-3123-2021, https://doi.org/10.5194/acp-21-3123-2021, 2021
Saly Jaber, Muriel Joly, Maxence Brissy, Martin Leremboure, Amina Khaled, Barbara Ervens, and Anne-Marie Delort
Biogeosciences, 18, 1067–1080, https://doi.org/10.5194/bg-18-1067-2021, https://doi.org/10.5194/bg-18-1067-2021, 2021
Short summary
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Our study is of interest to atmospheric scientists and environmental microbiologists, as we show that clouds can be considered a medium where bacteria efficiently degrade and transform amino acids, in competition with chemical processes. As current atmospheric multiphase models are restricted to chemical degradation of organic compounds, our conclusions motivate further model development.
Frédéric Mathonat, François Enault, Raphaëlle Péguilhan, Muriel Joly, Mariline Théveniot, Jean-Luc Baray, Barbara Ervens, and Pierre Amato
EGUsphere, https://doi.org/10.5194/egusphere-2025-3534, https://doi.org/10.5194/egusphere-2025-3534, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
Short summary
Short summary
The atmosphere plays key roles in Earth’s biogeochemical cycles. Airborne microbes were demonstrated previously to participate in the processing of organic carbon in clouds. Using a combinaison of complementary methods, we examined here, for the first time, their potential contribution to the pool of nitrogen compounds. Airborne microorganisms interact with abundant forms of nitrogen in the air and cloud and we provide global estimates.
Elsa Abs, Christoph Keuschnig, Pierre Amato, Chris Bowler, Eric Capo, Alexander Chase, Luciana Chavez Rodriguez, Abraham Dabengwa, Thomas Dussarrat, Thomas Guzman, Linnea Honeker, Jenni Hultman, Kirsten Küsel, Zhen Li, Anna Mankowski, William Riley, Scott Saleska, and Lisa Wingate
EGUsphere, https://doi.org/10.5194/egusphere-2025-1716, https://doi.org/10.5194/egusphere-2025-1716, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
Short summary
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Meta-omics technologies offer new tools to understand how microbial and plant functional diversity shape biogeochemical cycles across ecosystems. This perspective explores how integrating omics data with ecological and modeling approaches can improve our understanding of greenhouse gas fluxes and nutrient dynamics, from soils to clouds, and from the past to the future. We highlight challenges and opportunities for scaling omics insights from local processes to Earth system models.
Raphaëlle Péguilhan, Florent Rossi, Muriel Joly, Engy Nasr, Bérénice Batut, François Enault, Barbara Ervens, and Pierre Amato
Biogeosciences, 22, 1257–1275, https://doi.org/10.5194/bg-22-1257-2025, https://doi.org/10.5194/bg-22-1257-2025, 2025
Short summary
Short summary
Using comparative metagenomics and metatranscriptomics, we examined the functioning of airborne microorganisms in clouds and a clear atmosphere. Clouds are atmospheric masses where multiple microbial processes are promoted compared with a clear atmosphere. Overrepresented microbial functions of interest include the processing of chemical compounds, biomass production, and regulation of oxidants. This has implications for biogeochemical cycles and microbial ecology.
Barbara Ervens, Ken S. Carslaw, Thomas Koop, and Ulrich Pöschl
EGUsphere, https://doi.org/10.5194/egusphere-2025-419, https://doi.org/10.5194/egusphere-2025-419, 2025
Short summary
Short summary
Over the past two decades, the European Geosciences Union (EGU) has demonstrated the success, viability and benefits of interactive open access (OA) publishing with public peer review in its journals, its publishing platform EGUsphere and virtual compilations. The article summarizes the evolution of the EGU/Copernicus publications and of OA publishing with interactive public peer review at large by placing the EGU/Copernicus publications in the context of current and future global open science.
Barbara Ervens, Andrew Rickard, Bernard Aumont, William P. L. Carter, Max McGillen, Abdelwahid Mellouki, John Orlando, Bénédicte Picquet-Varrault, Paul Seakins, William R. Stockwell, Luc Vereecken, and Timothy J. Wallington
Atmos. Chem. Phys., 24, 13317–13339, https://doi.org/10.5194/acp-24-13317-2024, https://doi.org/10.5194/acp-24-13317-2024, 2024
Short summary
Short summary
Chemical mechanisms describe the chemical processes in atmospheric models that are used to describe the changes in the atmospheric composition. Therefore, accurate chemical mechanisms are necessary to predict the evolution of air pollution and climate change. The article describes all steps that are needed to build chemical mechanisms and discusses the advances and needs of experimental and theoretical research activities needed to build reliable chemical mechanisms.
Leslie Nuñez López, Pierre Amato, and Barbara Ervens
Atmos. Chem. Phys., 24, 5181–5198, https://doi.org/10.5194/acp-24-5181-2024, https://doi.org/10.5194/acp-24-5181-2024, 2024
Short summary
Short summary
Living bacteria comprise a small particle fraction in the atmosphere. Our model study shows that atmospheric bacteria in clouds may efficiently biodegrade formic and acetic acids that affect the acidity of rain. We conclude that current atmospheric models underestimate losses of these acids as they only consider chemical processes. We suggest that biodegradation can affect atmospheric concentration not only of formic and acetic acids but also of other volatile, moderately soluble organics.
Maud Leriche, Pierre Tulet, Laurent Deguillaume, Frédéric Burnet, Aurélie Colomb, Agnès Borbon, Corinne Jambert, Valentin Duflot, Stéphan Houdier, Jean-Luc Jaffrezo, Mickaël Vaïtilingom, Pamela Dominutti, Manon Rocco, Camille Mouchel-Vallon, Samira El Gdachi, Maxence Brissy, Maroua Fathalli, Nicolas Maury, Bert Verreyken, Crist Amelynck, Niels Schoon, Valérie Gros, Jean-Marc Pichon, Mickael Ribeiro, Eric Pique, Emmanuel Leclerc, Thierry Bourrianne, Axel Roy, Eric Moulin, Joël Barrie, Jean-Marc Metzger, Guillaume Péris, Christian Guadagno, Chatrapatty Bhugwant, Jean-Mathieu Tibere, Arnaud Tournigand, Evelyn Freney, Karine Sellegri, Anne-Marie Delort, Pierre Amato, Muriel Joly, Jean-Luc Baray, Pascal Renard, Angelica Bianco, Anne Réchou, and Guillaume Payen
Atmos. Chem. Phys., 24, 4129–4155, https://doi.org/10.5194/acp-24-4129-2024, https://doi.org/10.5194/acp-24-4129-2024, 2024
Short summary
Short summary
Aerosol particles in the atmosphere play a key role in climate change and air pollution. A large number of aerosol particles are formed from the oxidation of volatile organic compounds (VOCs and secondary organic aerosols – SOA). An important field campaign was organized on Réunion in March–April 2019 to understand the formation of SOA in a tropical atmosphere mostly influenced by VOCs emitted by forest and in the presence of clouds. This work synthesizes the results of this campaign.
Amina Khaled, Minghui Zhang, and Barbara Ervens
Atmos. Chem. Phys., 22, 1989–2009, https://doi.org/10.5194/acp-22-1989-2022, https://doi.org/10.5194/acp-22-1989-2022, 2022
Short summary
Short summary
Chemical reactions with iron in clouds and aerosol form and cycle reactive oxygen species (ROS). Previous model studies assumed that all cloud droplets (particles) contain iron, while single-particle analyses showed otherwise. By means of a model, we explore the bias in predicted ROS budgets by distributing a given iron mass to either all or only a few droplets (particles). Implications for oxidation potential, radical loss and iron oxidation state are discussed.
Pamela A. Dominutti, Pascal Renard, Mickaël Vaïtilingom, Angelica Bianco, Jean-Luc Baray, Agnès Borbon, Thierry Bourianne, Frédéric Burnet, Aurélie Colomb, Anne-Marie Delort, Valentin Duflot, Stephan Houdier, Jean-Luc Jaffrezo, Muriel Joly, Martin Leremboure, Jean-Marc Metzger, Jean-Marc Pichon, Mickaël Ribeiro, Manon Rocco, Pierre Tulet, Anthony Vella, Maud Leriche, and Laurent Deguillaume
Atmos. Chem. Phys., 22, 505–533, https://doi.org/10.5194/acp-22-505-2022, https://doi.org/10.5194/acp-22-505-2022, 2022
Short summary
Short summary
We present here the results obtained during an intensive field campaign conducted in March to April 2019 in Reunion. Our study integrates a comprehensive chemical and microphysical characterization of cloud water. Our investigations reveal that air mass history and cloud microphysical properties do not fully explain the variability observed in their chemical composition. This highlights the complexity of emission sources, multiphasic exchanges, and transformations in clouds.
Ramon Campos Braga, Barbara Ervens, Daniel Rosenfeld, Meinrat O. Andreae, Jan-David Förster, Daniel Fütterer, Lianet Hernández Pardo, Bruna A. Holanda, Tina Jurkat-Witschas, Ovid O. Krüger, Oliver Lauer, Luiz A. T. Machado, Christopher Pöhlker, Daniel Sauer, Christiane Voigt, Adrian Walser, Manfred Wendisch, Ulrich Pöschl, and Mira L. Pöhlker
Atmos. Chem. Phys., 21, 17513–17528, https://doi.org/10.5194/acp-21-17513-2021, https://doi.org/10.5194/acp-21-17513-2021, 2021
Short summary
Short summary
Interactions of aerosol particles with clouds represent a large uncertainty in estimates of climate change. Properties of aerosol particles control their ability to act as cloud condensation nuclei. Using aerosol measurements in the Amazon, we performed model studies to compare predicted and measured cloud droplet number concentrations at cloud bases. Our results confirm previous estimates of particle hygroscopicity in this region.
Soleil E. Worthy, Anand Kumar, Yu Xi, Jingwei Yun, Jessie Chen, Cuishan Xu, Victoria E. Irish, Pierre Amato, and Allan K. Bertram
Atmos. Chem. Phys., 21, 14631–14648, https://doi.org/10.5194/acp-21-14631-2021, https://doi.org/10.5194/acp-21-14631-2021, 2021
Short summary
Short summary
We studied the effect of (NH4)2SO4 on the immersion freezing of non-mineral dust ice-nucleating substances (INSs) and mineral dusts. (NH4)2SO4 had no effect on the median freezing temperature of 9 of the 10 tested non-mineral dust INSs, slightly decreased that of the other, and increased that of all the mineral dusts. The difference in the response of mineral dust and non-mineral dust INSs to (NH4)2SO4 suggests that they nucleate ice and/or interact with (NH4)2SO4 via different mechanisms.
Ramon Campos Braga, Daniel Rosenfeld, Ovid O. Krüger, Barbara Ervens, Bruna A. Holanda, Manfred Wendisch, Trismono Krisna, Ulrich Pöschl, Meinrat O. Andreae, Christiane Voigt, and Mira L. Pöhlker
Atmos. Chem. Phys., 21, 14079–14088, https://doi.org/10.5194/acp-21-14079-2021, https://doi.org/10.5194/acp-21-14079-2021, 2021
Short summary
Short summary
Quantifying the precipitation within clouds is crucial for our understanding of the Earth's hydrological cycle. Using in situ measurements of cloud and rain properties over the Amazon Basin and Atlantic Ocean, we show here a linear relationship between the effective radius (re) and precipitation water content near the tops of convective clouds for different pollution states and temperature levels. Our results emphasize the role of re to determine both initiation and amount of precipitation.
Mira L. Pöhlker, Minghui Zhang, Ramon Campos Braga, Ovid O. Krüger, Ulrich Pöschl, and Barbara Ervens
Atmos. Chem. Phys., 21, 11723–11740, https://doi.org/10.5194/acp-21-11723-2021, https://doi.org/10.5194/acp-21-11723-2021, 2021
Short summary
Short summary
Clouds cool our atmosphere. The role of small aerosol particles in affecting them represents one of the largest uncertainties in current estimates of climate change. Traditionally it is assumed that cloud droplets only form particles of diameters ~ 100 nm (
accumulation mode). Previous studies suggest that this can also occur in smaller particles (
Aitken mode). Our study provides a general framework to estimate under which aerosol and cloud conditions Aitken mode particles affect clouds.
Minghui Zhang, Amina Khaled, Pierre Amato, Anne-Marie Delort, and Barbara Ervens
Atmos. Chem. Phys., 21, 3699–3724, https://doi.org/10.5194/acp-21-3699-2021, https://doi.org/10.5194/acp-21-3699-2021, 2021
Short summary
Short summary
Although primary biological aerosol particles (PBAPs, bioaerosols) represent a small fraction of total atmospheric aerosol burden, they might affect climate and public health. We summarize which PBAP properties are important to affect their inclusion in clouds and interaction with light and might also affect their residence time and transport in the atmosphere. Our study highlights that not only chemical and physical but also biological processes can modify these physicochemical properties.
Amina Khaled, Minghui Zhang, Pierre Amato, Anne-Marie Delort, and Barbara Ervens
Atmos. Chem. Phys., 21, 3123–3141, https://doi.org/10.5194/acp-21-3123-2021, https://doi.org/10.5194/acp-21-3123-2021, 2021
Saly Jaber, Muriel Joly, Maxence Brissy, Martin Leremboure, Amina Khaled, Barbara Ervens, and Anne-Marie Delort
Biogeosciences, 18, 1067–1080, https://doi.org/10.5194/bg-18-1067-2021, https://doi.org/10.5194/bg-18-1067-2021, 2021
Short summary
Short summary
Our study is of interest to atmospheric scientists and environmental microbiologists, as we show that clouds can be considered a medium where bacteria efficiently degrade and transform amino acids, in competition with chemical processes. As current atmospheric multiphase models are restricted to chemical degradation of organic compounds, our conclusions motivate further model development.
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Short summary
Atmospheric microorganisms are a small fraction of Earth's microbiome, with bacteria being a significant part. Aerosolized bacteria are airborne for a few days, encountering unique chemical and physical conditions affecting stress levels and survival. We explore chemical and microphysical conditions bacteria encounter, highlighting potential nutrient and oxidant limitations and diverse effects by pollutants, which may ultimately impact the microbiome's role in global ecosystems and biodiversity.
Atmospheric microorganisms are a small fraction of Earth's microbiome, with bacteria being a...
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