| Congresso Brasileiro de Microbiologia 2023 | Resumo: 421-1 | ||||
Resumo:Recent data indicates that abundant salt deposits on Mars could contribute to meta-stable brines on the surface, which led to speculations about this environment supporting some form of halophilic life. Nevertheless, the average surface temperature of these possible brines would fall outside the known tolerances for terrestrial life.Thus, despite the presence of possible liquid water over the Martian surface, the generally low temperature of the planet would still be the main limitation factor for life as we know it. On the other hand, during summertime, temperatures can range from −63 ◦C at night to 30 ◦C at noon, presenting a milder environment in terms of temperature as a limiting factor for life on Earth. Therefore, understanding how halophiles behave when facing freeze-thaw events simulating a summer day on Mars is of great interest regarding martian habitability. For that, we expose two halophilic bacteria, Staphylococcus nepalensis and Chromohalobacter salexigens, isolated from a hypersaline lagoon in Rio de Janeiro (Brazil), to repeated freeze thaw cycles in two different conditions: (1) freeze-thaw cycle 12h/12h regime that includes the 12h thawing as a recovery interval; and (2) successive freeze-thaw regime, without the recovery phase. All cultures were carried out under LB Saline Media (LB media supplemented with 1.37 mol.L-1) and the survival response was measured by CFU counting from samples taken before every thawing phase. Our results have shown that the freeze-thaw cycle is harmering for the selected halophiles, but not lethal even after 10 cycles. Moreover, in the presence of the recovery phase, given under the first freeze-thaw regime, those isolates were capable of growth. Therefore, despite the evidence of severe damage caused by freeze-thaw cycling, these halophiles are capable of growing under simulated summer days temperatures on Mars. Palavras-chave: Freeze-thaw, Brines, Extremophiles Agência de fomento:CNPq | |||||