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Properties relevant to atmospheric dispersal of the ice-nucleation active Pseudomonas syringae strain R10.79 isolated from rain water

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Transport of microbes in the atmosphere allows them to spread and to colonize new habitats. To survive the harsh environmental conditions encountered in the atmosphere, these microorganisms have to possess properties that allow them to resist atmospheric stress. We combined physiological experiments and genome analysis of Pseudomonas syringae strain R10.79, previously isolated from rain, to decipher the strain’s ability to withstand these challenges and identify the mechanisms behind the resistance. We used laboratory experiments to simulate different atmospheric stress factors and evaluated cell survival using fluorescent staining and flow cytometry. We found that while P. syringae R10.79 was resistant to oxidative, osmotic, UVB radiation-induced and freezing stress, it was sensitive to desiccation on surfaces. Strain R10.79 possesses a range of genes that would allow the strain to mitigate atmospheric stresses, such as cold shock and osmotic shock genes as well as genes encoding for properties that relate to UV irradiation resistance. Studying the substrate spectrum of strain R10.79, we uncovered that it can utilize carbon compounds abundant in the atmosphere including acetate, succinate and formate. In addition, strain R10.79 possesses metabolic pathways to utilize formaldehyde and methanol as sole carbon sources. These compounds could support the metabolic activity of strain R10.79 while suspended in the atmosphere during periods with sufficiently high relative humidity. Finally, we found that when growing on acetate, strain R10.79 produces several volatile organic compounds such as isoprene and methanol, for which we propose biochemical pathways and which are relevant for atmospheric chemistry and climate. The results reported in this study will support our general aim at establishing this strain as a model organism to study microbial responses to atmospheric conditions.

Original languageEnglish
Pages (from-to)225-241
Number of pages17
Publication statusPublished - 2021

Bibliographical note

Funding Information:
This work was supported by The Danish National Research Foundation (Grant Agreement No. DNRF106, to the Stellar Astrophysics Centre, Aarhus University), the AUFF Nova programme (AUFF-E-2015-FLS-9-10) and by the Villum Fonden (Research Grant 23175). Flow cytometry was performed at the FACS Core Facility, Aarhus University, Denmark. The authors thank R. Bossi, M. Bilde and A. Feilberg for the opportunity to use the PTR-TOF-MS instrument. We gratefully acknowledge C. C. Petersen for her support with the interpretation of the flow cytometry data and A. Stentebjerg for her excellent technical support. We also appreciate the physiological data provided by S. Pilgaard.

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature.

Copyright 2021 Elsevier B.V., All rights reserved.

    Research areas

  • Atmospheric chemistry, Atmospheric dispersal, Atmospheric stress, Draft genome, Ice-nucleation activity, Metabolism, Pseudomonas syringae

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