Halobacterium lacusprofundi sp. nov., a Halophilic Bacterium Isolated from Deep Lake, Antarctica

Halobacterium lacusprofundi sp. nov. is described based on the characteristics of two strains (ACAM 32, ACAM 34) of red halophilic bacteria isolated from Deep Lake, a hypersaline, Antarctic lake. Bacteria which could grow on media prepared with undiluted Deep Lake water have not been isolated previously from Deep Lake. Cells were pleomorphic rods which lysed when suspended in distilled water. Unlike other halobacteria, the strains grew at 4°C, albeit very slowly. Fastest generation times (11 h) occurred between 31–37°C. The strains were not proteolytic, did not produce acids from sugars, but utilized a wide range of carbon sources including sugars, alcohols, and organic acids for growth. The strains grew in media with Mg ++ concentrations ranging from 0.005 to 1.0 mol/l and with NaCl concentrations ranging from 1.5 mol/l to saturation. Cells contained isoprenoid neutral lipids typical of halophilic archaebacteria. The major constituents were diphytanyl glyceryl ether, squalene and dihydrophytol. Approximately 30% of the total ether lipids consisted of at least four glyceryl ethers containing one or more double bonds in the phytenyl group. Also present were squalane, dihydrosqualene, tetrahydrosqualene, dihydrophytol and phytol. The G+C content of the major component DNA was 65 to 66 mol%. Satellite band DNA was present with G+C contents ranging from 54 to 57 mol%. Analysis of the 16S rRNA catalogue showed strain ACAM 34 was most closely related to Halobacterium saccharovorum ATCC 29252 (S AB value 0.74) but only distantly related to Haloferax volcanii ATCC 29605 (S AB value 0.43), Haloarcula vallismortis ATCC 29715 (S AB value 0.36), Halococcus morrhuae ATCC 17082 (S AB value 0.39) or Natronococcus occultus NCMB 2192 (S AB value 0.47). The type strain is UQM 3107 (ACAM 34).