Potential for preservation of Halobacteria and their macromolecular constituents in brine inclusions from bedded salt deposits

Halobacteria cultured from salt deposits as old as 200 m.y. were assumed to be dormant halobacteria entombed in the brine inclusions that formed during deposition of the salt crystals. Hypersaline lakes may have also existed on early Mars. If so, evaporite minerals containing frozen brine inclusions may occur on the surface of Mars today. Analyses of samples of recently-deposited salt from Laguna Grande de la Sal in New Mexico revealed the presence of viable halobacteria. 16S rDNA from archae and eubacteria was also detected by polymerase chain reaction (PCR) amplification of directly-extracted DNA from Laguna Grande de la Sal sal. In contrast, no halophilic bacteria were cultured from 200 my polyhalite from the Salado Formation in New Mexico nor was archaea 16S rDNA detected by PCR amplification of DNA extracts from salt. A combination of microbiological, molecular, and geochemical approaches are being used to probe bedded salt deposits for evidence of microbial entrapment in primary fluid inclusions. A chronosequence of bedded salts from Death Valley, California that range in age from 0 to 200 kyr is the subject of current investigations to constrain the length of time that viable halophilic bacteria and associated macromolecules can be detected in bedded salts.