Survival of salinotolerant bacteria in brines relevant to Mars at low temperatures nonpermissive for growth

Abstract

The limits at which life can occur in our world may not be the same in other worlds. A common theme in astrobiology is to search for potential habitable regions beyond Earth, and by developing a better understanding of these limits at which life can occur we are able to narrow our search to focus on the area’s most likely to harbor life. To find life humankind must search for water and examine where it has been or is currently. Using microbiology and the uniquely available salty regions on Earth, we can further our understanding of these environments, the microorganisms that inhabit them, and similar locations on other worlds. The conditions of interest here are near the eutectic points of some relevant salt brines expected to be present in special regions near Mars’ surface. The most relevant salts which were examined specifically include 24 wt% and 1 wt% NaCl, 25 wt% LiCl, 39 wt% NaClO3, 44 wt% Mg(ClO4)2, and 52 wt% NaClO4 (Table 32 and Table 33) tested with known organisms identified as Marinococcus sp. str. HL11, Halomonas sp. str. BLE7 (Figure 4), and Halomonas sp. str. GSP3 (Table 31). All 3 species were examined in each salt brine at room temperature (control) and -20 °C, while the LiCl and (per)chlorates are subjected to -40 °C as well due to the freezing point depression. The implications of microbial survivability have relevance ranging from extremophile biology, exobiology, multidirectional planetary protection, life detection, pathogenicity, salinotolerance and psychrotolerant microbiology specifically, as well as fulfilling the search to figure out whether there is life beyond Earth. Microbiology and current technology supply a method to quantify the robustness of growth in these various salt brines, which enhances our current understanding of the ability and limitations of these organisms to survive in these conditions; thus, furthering our current understanding of the limits at which life can survive, whether bound by Earth or not.