Roseovarius tolerans gen. nov., sp. nov., a budding bacterium with variable bacteriochlorophyll a production from hypersaline Ekho Lake

Eight Gram-negative, aerobic, pointed and budding bacteria were isolated fr om various depths of the hypersaline, heliothermal and meromictic Ekho Lake (Vestfold Hills, East Antarctica). The cells contained storage granules an d daughter cells could be nrotile. Bacteriochlorophyll a was sometimes prod uced, but production was repressed by constant dim light. The strains toler ated a wide range of temperature, pH, concentrations of artificial seawater and NaCl, but had an absolute requirement for sodium ions. Glutamate was m etabolized with and without an additional source of combined nitrogen. The dominant fatty acid was C-18:1; other characteristic fatty acids were C-18: 2, C-12:0, 2-OH, C-12:1 3-OH, C-16:1, C-16:0, and C-18:0. The main polar li pids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylgly cerol and phosphatidylcholine. The DNA G+C base composition was 62-64 mol%, 16S rRNA gene sequence comparisons showed that the isolates were phylogene tically close to the genera Antarctobacter, 'Marinosulfonomonas', Octadecab acter, Sagittula, Sulfitobacter and Roseobacter, Morphological, physiologic al and genotypic differences to these previously described and distinct gen era support the description of a new genus and a new species, Roseovarius t olerans gen, nov., sp, nov. The type strain is EL-172(T)(= DSM 11457(T)).