Survival, DNA Integrity, and Ultrastructural Damagein Antarctic Cryptoendolithic Eukaryotic MicroorganismsExposed to Ionizing Radiation
Claudia Pacelli ; Laura Selbmann ; Laura Zucconi ; et al. ; - ASI Sponsor
Feb - 2017
DOI: 10.1089/ast.2015.1456

journal : Astrobiology

Volume : 17 ; Issue : 2
type: Article Journal

Life dispersal between planets, planetary protection, and the search for biosignatures are main topics in astrobiology. Under the umbrella of the STARLIFE project, three Antarctic endolithic microorganisms, the melanized fungus Cryomyces antarcticus CCFEE 515, a hyaline strain of Umbilicaria sp. (CCFEE 6113, lichenized fungus), and a Stichococcus sp. strain (C45A, green alga), were exposed to high doses of space-relevant gamma radiation (60Co), up to 117.07 kGy. After irradiation survival, DNA integrity and ultrastructural damage were tested. The first was assessed by clonogenic test; viability and dose responses were reasonably described by the linear-quadratic formalism. DNA integrity was evaluated by PCR, and ultrastructural damage was observed by transmission electron microscopy. The most resistant among the tested organisms was C. antarcticus both in terms of colony formation and DNA preservation. Besides, results clearly demonstrate that DNA was well detectable in all the tested organisms even when microorganisms were dead. This high resistance provides support for the use of DNA as a possible biosignature during the next exploration campaigns. Implication in planetary protection and contamination during long-term space travel are put forward. Key Words: Biosignatures—Ionizing radiation—DNA integrity—Eukaryotic microorganisms—Fingerprinting—Mars exploration. Astrobiology 17, 126–135.

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Notes : Acknowledgments[...] The ASI (Italian Space Agency)and the PNRA (Italian National Antarctic Research Program)are kindly acknowledged for supporting the study [...]