Universität zu Köln

Horne, William H., Volpe, Robert P., Korza, George, DePratti, Sarah, Conze, Isabel H., Shuryak, Igor, Grebenc, Tine, Matrosova, Vera Y., Gaidamakova, Elena K., Tkavc, Rok, Sharma, Ajay, Gostincar, Cene, Gunde-Cimerman, Nina, Hoffman, Brian M., Setlow, Peter and Daly, Michael J. (2022). Effects of Desiccation and Freezing on Microbial Ionizing Radiation Survivability: Considerations for Mars Sample Return. Astrobiology, 22 (11). S. 1337 - 1351. NEW ROCHELLE: MARY ANN LIEBERT, INC. ISSN 1557-8070

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Abstract

Increasingly, national space agencies are expanding their goals to include Mars exploration with sample return. To better protect Earth and its biosphere from potential extraterrestrial sources of contamination, as set forth in the Outer Space Treaty of 1967, international efforts to develop planetary protection measures strive to understand the danger of cross-contamination processes in Mars sample return missions. We aim to better understand the impact of the martian surface on microbial dormancy and survivability. Radiation resistance of microbes is a key parameter in considering survivability of microbes over geologic times on the frigid, arid surface of Mars that is bombarded by solar and galactic cosmic radiation. We tested the influence of desiccation and freezing on the ionizing radiation survival of six model microorganisms: vegetative cells of two bacteria (Deinococcus radiodurans, Escherichia coli) and a strain of budding yeast (Saccharomyces cerevisiae); and vegetative cells and endospores of three Bacillus bacteria (B. subtilis, B. megaterium, B. thuringiensis). Desiccation and freezing greatly increased radiation survival of vegetative polyploid microorganisms when applied separately, and when combined, desiccation and freezing increased radiation survival even more so. Thus, the radiation survival threshold of polyploid D. radiodurans cells can be extended from the already high value of 25 kGy in liquid culture to an astonishing 140 kGy when the cells are both desiccated and frozen. However, such synergistic radioprotective effects of desiccation and freezing were not observed in monogenomic or digenomic Bacillus cells and endospores, which are generally sterilized by 12 kGy. This difference is associated with a critical requirement for survivability under radiation, that is, repair of genome damage caused by radiation. Deinococcus radiodurans and S. cerevisiae accumulate similarly high levels of the Mn antioxidants that are required for extreme radiation resistance, as do endospores, though they greatly exceed spores in radioresistance because they contain multiple identical genome copies, which in D. radiodurans are joined by persistent Holliday junctions. We estimate ionizing radiation survival limits of polyploid DNA-based life-forms to be hundreds of millions of years of background radiation while buried in the martian subsurface. Our findings imply that forward contamination of Mars will essentially be permanent, and backward contamination is a possibility if life ever existed on Mars.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Horne, William H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Volpe, Robert P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Korza, George UNSPECIFIED UNSPECIFIED UNSPECIFIED DePratti, Sarah UNSPECIFIED UNSPECIFIED UNSPECIFIED Conze, Isabel H. UNSPECIFIED UNSPECIFIED UNSPECIFIED Shuryak, Igor UNSPECIFIED UNSPECIFIED UNSPECIFIED Grebenc, Tine UNSPECIFIED UNSPECIFIED UNSPECIFIED Matrosova, Vera Y. UNSPECIFIED UNSPECIFIED UNSPECIFIED Gaidamakova, Elena K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Tkavc, Rok UNSPECIFIED UNSPECIFIED UNSPECIFIED Sharma, Ajay UNSPECIFIED UNSPECIFIED UNSPECIFIED Gostincar, Cene UNSPECIFIED UNSPECIFIED UNSPECIFIED Gunde-Cimerman, Nina UNSPECIFIED UNSPECIFIED UNSPECIFIED Hoffman, Brian M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Setlow, Peter UNSPECIFIED UNSPECIFIED UNSPECIFIED Daly, Michael J. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-690721
DOI:	10.1089/ast.2022.0065
Journal or Publication Title:	Astrobiology
Volume:	22
Number:	11
Page Range:	S. 1337 - 1351
Date:	2022
Publisher:	MARY ANN LIEBERT, INC
Place of Publication:	NEW ROCHELLE
ISSN:	1557-8070
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language OXIDATIVE STRESS RESISTANCE; DEINOCOCCUS-RADIODURANS; BACILLUS-SUBTILIS; RECOMBINATION; SPORES; DNA; PROTECTION; SURVIVE; REPAIR; DAMAGE Multiple languages Astronomy & Astrophysics; Biology; Geosciences, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/69072