Evaluation of the Resistance of Chroococcidiopsis spp. to Sparsely and Densely Ionizing Irradiation

Studying the resistance of cyanobacteria to ionizing radiation provides relevant information regardingastrobiology-related topics including the search for life on Mars, lithopanspermia, and biological life-supportsystems. Here, we report on the resistance of desert cyanobacteria of the genusChroococcidiopsis,which wereexposed (as part of the STARLIFE series of experiments) in both hydrated and dried states to ionizing radiationwith different linear energy transfer values (0.2 to 200 keV/mm). Irradiation with up to 1 kGy of He or Si ions,2 kGy of Fe ions, 5 kGy of X-rays, or 11.59 kGy ofcrays (60Co) did not eradicateChroococcidiopsispopu-lations, nor did it induce detectable damage to DNA or plasma membranes. The relevance of these results forastrobiology is briefly discussed. Key Words: Ionizing radiation—Linear energy transfer—Lithopanspermia—Cyanobacterial radioresistance—Chroococcidiopsis—Mars. Astrobiology 17, xxx–xxx.