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Bacillus subtilis Spore Resistance to Simulated Mars Surface Conditions

Cortesao, Marta and Fuchs, Felix M. and Commichau, Fabian M. and Eichenberger, Patrick and Schuerger, Andrew C. and Nicholson, Wayne L. and Setlow, Peter and Moeller, Ralf (2019) Bacillus subtilis Spore Resistance to Simulated Mars Surface Conditions. Frontiers in Microbiology, 10. Frontiers Media S.A.. DOI: 10.3389/fmicb.2019.00333 ISSN 1664-302X

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Official URL: http://dx.doi.org/10.3389/fmicb.2019.00333

Abstract

In a Mars exploration scenario, knowing if and how highly resistant Bacillus subtilis spores would survive on the Martian surface is crucial to design planetary protection measures and avoid false positives in life-detection experiments. Therefore, in this study a systematic screening was performed to determine whether B. subtilis spores could survive an average day on Mars. For that, spores from two comprehensive sets of isogenic B. subtilis mutant strains, defective in DNA protection or repair genes, were exposed to 24 h of simulated Martian atmospheric environment with or without 8 h of Martian UV radiation [M(+)UV and M(-)UV, respectively]. When exposed to M(+)UV, spore survival was dependent on: (1) core dehydration maintenance, (2) protection of DNA by α/β-type small acid soluble proteins (SASP), and (3) removal and repair of the major UV photoproduct (SP) in spore DNA. In turn, when exposed to M(-)UV, spore survival was mainly dependent on protection by the multilayered spore coat, and DNA double-strand breaks represent the main lesion accumulated. Bacillus subtilis spores were able to survive for at least a limited time in a simulated Martian environment, both with or without solar UV radiation. Moreover, M(-)UV-treated spores exhibited survival rates significantly higher than the M(+)UV-treated spores. This suggests that on a real Martian surface, radiation shielding of spores (e.g., by dust, rocks, or spacecraft surface irregularities) might significantly extend survival rates. Mutagenesis were strongly dependent on the functionality of all structural components with small acid-soluble spore proteins, coat layers and dipicolinic acid as key protectants and efficiency DNA damage removal by AP endonucleases (ExoA and Nfo), non-homologous end joining (NHEJ), mismatch repair (MMR) and error-prone translesion synthesis (TLS). Thus, future efforts should focus on: (1) determining the DNA damage in wild-type spores exposed to M(+/-)UV and (2) assessing spore survival and viability with shielding of spores via Mars regolith and other relevant materials.

Item URL in elib:https://elib.dlr.de/126829/
Document Type:Article
Title:Bacillus subtilis Spore Resistance to Simulated Mars Surface Conditions
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Cortesao, MartaRadiation Biology Department, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany; Marta.Cortesao (at) dlr.deUNSPECIFIED
Fuchs, Felix M.Radiation Biology Department, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany; felix.fuchs (at) dlr.dehttps://orcid.org/0000-0001-5669-5655
Commichau, Fabian M.Department of General Microbiology, Institute for Microbiology and Genetics, University of Göttingen, Göttingen, GermanyUNSPECIFIED
Eichenberger, PatrickDepartment of Biology, Center for Genomics and Systems Biology, New York University, New York, NY, United StatesUNSPECIFIED
Schuerger, Andrew C.Department of Plant Pathology, Space Life Sciences Laboratory, University of Florida, Merritt Island, FL, United StatesUNSPECIFIED
Nicholson, Wayne L.Department of Microbiology and Cell Science, Space Life Sciences Laboratory, University of Florida, Merritt Island, FL, United StatesUNSPECIFIED
Setlow, PeterDepartment of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, United StatesUNSPECIFIED
Moeller, RalfRadiation Biology Department, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany; ralf.moeller (at) dlr.dehttps://orcid.org/0000-0002-2371-0676
Date:26 February 2019
Journal or Publication Title:Frontiers in Microbiology
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:10
DOI :10.3389/fmicb.2019.00333
Publisher:Frontiers Media S.A.
ISSN:1664-302X
Status:Published
Keywords:Bacillus subtilis, spore resistance, DNA repair, SASP, Mars, contamination, radiation, planetary protection
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):R - Vorhaben Strahlenbiologie
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine > Radiation Biology
Deposited By: Kopp, Kerstin
Deposited On:28 Mar 2019 11:56
Last Modified:28 Mar 2019 11:56

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