Partial protection of Bacillus subtilis spores on simulated Martian media enhances survival against UV radiation

Abstract Mars is known to have once sustained an environment that may have been habitable. This idea has often been combined with theories of panspermia, to suggest that any life on Mars may have had a common origin with life on Earth. These ideas typically involve meteorites produced as impact ejecta as vectors for the transport of life between planets. However, such meteorites would be subjected to the harsh conditions of space, most notably, Solar UV radiation. Some Gram-positive bacteria generate endospores, which provide protection from extreme conditions and are common models for understanding bacterial survival in space. In this study, the spore forming bacteria Bacillus subtilis and the non-spore former Staphylococcus aureus were used to investigate the survival of bacteria exposed to UVB and UVC radiation on simulated Martian regolith. Spore survival was limited upon excessive doses of UVB and UVC radiation, although this was minimised when spores were covered with lysed bacteria which provided partial protection. These results build upon previous studies and suggest that lysed bacteria from the same bacterial species might offer spores on Martian meteorites a partial shield from UV radiation and enhance their viability in panspermia models.