THE PHYSIOLOGICAL RESPONSE OF BUTTIAUXELLA SP. MASE-IM-9 AND SALINISPHAERA SHABANENSIS FROM MARS-LIKE ENVIRONMENTS ON EARTH TO PERCHLORATES

Kurzfassung

The habitability of Mars has been a topic of great interest in the field of astrobiology. One key aspect of habitability is the presence of liquid water, which is considered crucial for life as we know it. Recent discoveries have provided strong evidence for the existence of liquid water on Mars, albeit in small amounts and in specific locations such as underground reservoirs and seasonally ocurring brines. However, the presence of perchlorates on the Martian surface raises concerns about the habitability of these water sources. Perchlorates are known to be oxidizing compounds and cause deliquescence, the ability to absorb water vapor from the atmosphere, resulting in hypersaline conditions. Understanding the effects of perchlorates on terrestrial organisms is vital in the context of forward planetary protection. Investigating the response of Earth-based life forms to perchlorates can inform our understanding of potential Martian life and the challenges it may face in this unique environment. This study aimed to investigate and enhance our understanding of the tolerance of two bacterial strains, Buttiauxella sp. MASE-IM-9 and Salinisphaera shabanensis, to perchlorates, which were isolated from Mars-like environments on Earth. The strains were subjected to various stress factors relevant to Mars conditions. Both strains demonstrated the ability to survive and grow in Mars-like concentrations of sodium and magnesium perchlorates. Salinisphaera cells exhibited higher tolerance to perchlorates, supporting the notion that halophilic organisms are better adapted to osmotic and oxidative stress. Proteomic analysis of Buttiauxella revealed a specific stress response to perchlorates, with proteins regulated differently from the response to chloride salts. One notable finding was the upregulation of a copper-efflux pump, suggesting that endogenous copper accumulated within the cell when exposed to perchlorates. This is the second study to observe the upregulation of a copper efflux pump in response to environmental stress without any addition of copper to the medium. Further investigations are required to understand the mechanisms underlying this strategy. Overall, these experiments contribute to our knowledge of the specific tolerance and physiological response of microorganisms to perchlorates. This information has implications not only for astrobiology and space exploration but also for utilizing microbes in the bioremediation of perchlorates on Earth.