Isolation and Characterization of Halophilic Heterotrophic Bacteria from Lake Vanda, McMurdo Dry Valleys, Antarctica

Lake Vanda is a meromictic, permanently ice-covered lake in the McMurdo Dry Valleys. The McMurdo Dry Valleys are a polar desert in Southern Victorialand Antarctica. This area experiences very little rainfall and very cold average temperatures, around –20°C. Lake Vanda has an unusual limnological profile, with a sharp physical and chemical gradient at about 60 m where the water transitions from cold, oxic, and fresh, to warm, hypersaline, and sulfidic; CaCl2 rather than NaCl is the dominant salt. Aerobic enrichment techniques were used to isolate what turned out to be several strains of a species of Chromohalobacter, a genus of the Gammaproteobacteria, from Lake Vanda deep waters, while targeted enrichments for anaerobic and spore-forming bacteria were negative. The isolates were characterized for their temperature and pH optima, carbon and nitrogen nutrition, and salt tolerance and requirements. The results showed the organisms to be obligately aerobic with a broad pH range (optima pH 7). The isolates used some sugars and organic acids but not alcohols or fatty acids for energy and cell carbon, and showed a moderate requirement for NaCl but no requirement for CaCl2, even though CaCl2 is the predominant salt in their environment