Four species of non-spore-forming bacteria collected from clean-room surfaces in spacecraft-assembly facilities could survive doses of ultraviolet (UV) radiation that would suffice to kill most known cultivable bacterial species. In a previous study, high UV resistance was found in spores of the SAFR-032 strain of Bacillus pumilus, as reported in “Ultraviolet-Resistant Bacterial Spores,” NASA Tech Briefs, Vol. 31, No. 9 (September 2007), page 94. These studies are parts of a continuing effort to understand the survival of hardy species of bacteria under harsh conditions, and develop means of sterilizing spacecraft to prevent biocontamination of Mars that could in turn interfere with future life detection missions.
The four species investigated were Arthrobacter sp. KSC_Ak2i, Microbacterium schleiferi LMA_AkK1, Brevundimonas diminuta KSC_Ak3a, and Sphingomonas trueperi JSC_Ak7-3. In the study, cells of these species were mixed into Atacama Desert soil (to elucidate the shadowing effect of soil particles) and the resulting mixtures were tested both in solution and in a desiccated state under simulated Martian atmospheric and UV conditions. The UV-survival indices of Arthrobacter sp. and Microbacterium schleiferi were found to be comparable to those of Bacillus pumilus spores.