Astrobiology with haloarchaea from Permo-Triassic rock salt

Abstract

Several viable halophilic archaebacteria were isolated previously from rock salt of Permo-Triassic age in an Austrian salt mine; one of these strains was the first to be recognized as a novel species from subterranean halite and was designated Halococcus salifodinae. The halophilic microorganisms have apparently survived in the salt sediments over extremely long periods of time. Halobacteria could therefore be suitable model organisms for exploring the possibility of long-term survival of microbes on other planets, in particular, since extraterrestrial halite has been detected in meteorites and is assumed to be present in the subsurface ocean on Europa. Our efforts are directed at the identification of the microbial content of ancient rock salt and the development of procedures for the investigation of the halobacterial response to extreme environmental conditions. Using modified culture media, further halophilic strains were isolated from freshly blasted rock salt and bore cores; in addition, growth of several haloarchaea was substantially improved. Molecular methods indicated the presence of at least 12 different 16S rRNA gene species in a sample of Alpine rock salt, but these strains have not been cultured yet. The exploration of Mars is a target of space missions in the 21st century; therefore, testing the survival of haloarchaea under conditions comparable to present-day Mars, using a simulation chamber, was begun. Preliminary results with Halococcus and Halobacterium species suggested at least tenfold higher survival rates when cells were kept in liquid brines than under dry conditions; staining of cells with the LIVE–DEAD kit, which discriminates between damaged and intact membranes, corroborated these data.

Effects of Long-Term Simulated Martian Conditions on a Freeze-Dried and Homogenized Bacterial Permafrost Community

“…This indicates that an extended period of vacuum and low temperature were not detrimental for either the cells or biomolecules. Previous studies have shown that freeze-drying of cells reduces bacterial viability (Stan-Lotter et al, 2003;Hansen et al, 2005). Freeze-drying also caused a slight reduction in the number of viable cells in the present study (3.2 ϫ 10 8 cells gdw Ϫ1 in the control) compared to 4.4 ϫ 10 8 cells gdw Ϫ1 in the original permafrost (Hansen et al, 2007).…”

Thermal Diapirism and the Habitability of the Icy Shellof Europa

“…3), since these substances are efficient cryoprotectants (Welsh 2000;Elbein et al 2003;Cleland et al 2004;Yancey 2005). In a similar way, Stan-Lotter et al (2003) have experimentally shown that the presence of glycerol enhances the survival rate of halophilic archeobacteria during deep freezingdrying in simulated Martian atmosphere conditions.…”

Earth's perennially frozen environments as a model of cryogenic planet ecosystems

“…There are a number of environments in the biosphere that could preserve viable microorganisms over geological time. Comparisons of the number of viable microorganisms preserved in galite and amber at temperatures above 0°С with those preserved in the cryosphere at temperatures below 0°С have shown that the cryosphere hosts a larger amount of extremely diverse viable microorganisms …”