PHYSIOLOGICAL, BIOCHEMICAL AND PHYLOGENETIC CHARACTERIZATION OF EXTREMELY HALOPHILIC BACTERIA ISOLATED FROM KHEWRA MINE, PAKISTAN

Microflora entrapped in the salt deposits of Khewra salt mine, Pakistan has adapted to extreme conditions and nutrient scarcity to survive. Due to assumption that halophilic archaea dominate hypersaline environments, bacteria have often remained unexplored. The reports on extremely halophilic bacteria indigenous to Khewra mine are quite limited resulting in largely unexplored biodiversity of the salt mine. Here we attempted to fill that gap by isolating eight halophilic bacteria, out of which four extremely halophilic bacteria were selected for physiological, biochemical and molecular characterization. The phylogenetic characterization inferred through comparative partial 16S rRNA sequences identified these strains as HSL1-Oceanobacillus onchorhynci subsp. Incaldanensis, HSL4-Staphylococcus lentus, HSL6-Bacillus endophyticus and HSL7-Bacillus aquimaris. These isolates could tolerate a wide range of temperatures (15-45 degrees C), pH (5-9) and survived up to 16% NaCl concentration. This tolerance is due to the stability of their enzymes. Enzyme assays revealed a substantial amount of production of protease, amylase, lipase, xylanase, urease, gelatinase, cellulose, and DNase. Conclusively, isolation and characterization of the extremely halophilic bacteria from Khewra mine indicated their important ecological role and contribution towards the microbial diversity. The ability to produce extreme-enzymes also established the potential of the isolates as valuable resources for significant biotechnological applications.