Mining Bacterial Strains from a Rock Salt Mine for Halotolerance Genes and Enzymes

Abstract

Halophiles are organisms adapted to thrive in extreme conditions of salinity, distributed all over the world in hypersaline environments, which includes hypersaline brines in arid, coastal, and even deep sea locations, as well as in rock salt mines. The intracellular machinery of these prokaryotes has evolved to function at very high salt concentrations. During recent years, these halophiles have been considered of great interest because of their biotechnological potential, notably for producing genes and enzymes of industrial interest and accumulating a variety of organic compounds, called compatible solutes, useful as enzymes or cell stabilizing agents. Moreover, microorganisms are themselves used in various biotechnological applications (e.g. bioremediation). In the present study, we have isolated nine halotolerant strains from a rock salt mine at Darang, H.P., with a view to provide insight on the possibility to use different halophiles as a source of extremophilic genes/enzymes in biotechnological processes. The strains were named as JPBW-1 to JPBW-10 (JPBW- Jaypee Biotech Waknaghat). The results of the test for halotolerance revealed that the strains JPBW-1 and JPBW-9 were extremely halotolerant (19.0%) while rest of the strains was moderately halotolerant (7.0-12.0%). Strains were identified on the basis of 16S rRNA gene sequencing which confirmed that all the strains were bacteria belonging to the phylum Firmicutes. Homology search results for 16S rRNA gene sequences showed that the nine strains consisted of one strain of Staphylococcus arlettae, three strains of Bacillus licheniformis, one Bacillus amyloliquefaciens and four strains of Bacillus subtilis. Comparative analysis of halotolerance proteins retrieved from published literature to identify signature residues or specific properties revealed that the regulators of ion transporters (29.0 %) were the most predominant family of proteins involved in halotolerance among halophiles followed by transporters (24.0%). newline