Extremophiles for Astrobiology studies

Astrobiology studies the origin and evolution of life on Earth and in the Universe. According to the panspermia theory (Zagorski 2007a), life on Earth could have emerged after transfer of extraterrestrial life forms (most probably microorganisms) transported by radiation pressure or by meteorites on the Earth's surface. The transfer from one planet to another requires the ability to survive to several extreme environmental parameters (absence of oxygen, of water and of gravity; exposition to ionizing radiations; extreme temperature's variations, etc). Therefore, the study of extremophiles, i.e. bacterial species able to live in conditions incompatible with life from an anthropocentric point of view, can be relevant to Astrobiology studies: their ability to live in extreme conditions suggests that most probably extremophiles have been among the first living organisms that colonized the Earth. For these reasons they are the object of attention for astrobiology researches (Moissl-Eichinger et al. 2016b). Here, we reported the ability of the thermophilic species Geobacillus thermantarcticus (a bacterium isolated from Mount Melbourne, an active volcano in Antarctica) to survive after exposition to simulated spatial conditions (temperature's variation, desiccation, X-rays and UVC irradiation). The response to the exposition to the space conditions was assessed at a molecular level by studying the changes in the morphology, the lipid and protein patterns, the nucleic acids. G. thermantarcticus survived to the exposition to all the stressing conditions tested, since it was able to restart cellular growth in comparable levels to control experiments carried out in the optimal growth conditions. These results suggested that G. thermantarcticus could be a good biological model for astrobiology studies since it is able to repair the possible modifications induced by stressing space conditions thus counteracting the harmful effects of exposition to space conditions (Mastascusa et al. 2014c; Di Donato et al., 2017d).