Psychroflexus salis sp. nov. and Psychroflexus planctonicus sp. nov., isolated from a salt lake

Two Gram-stain-negative, catalase- and oxidase-positive, strictly aerobic, non-motile, moderately halophilic bacteria (strains X15M-6T and X15M-8T) were isolated from Lake Xiaochaidan, a salt lake in Qaidam basin, Qinghai Province, China. Cells of X15M-6T were rod-like or coccoid, 0.5-0.9 μm wide and 0.9-1.5 μm long; cells of X15M-8T were rods, 0.3-0.6 μm wide and 1.2-2.2 μm long. Growth was observed in the presence of 0.5-14.0 % (w/v) NaCl (optimum, 3.0 %) and at pH 6.5-10.0 (optimum, pH 7.0-7.5) for both. X15M-6T and X15M-8T grew at 10-35 °C (optimum, 20-25 °C) and 4-35 °C (optimum, 25 °C), respectively. Both contained iso-C15 : 0, anteiso-C15 : 0 and iso-C17 : 0 3-OH as the major fatty acids, phosphatidylethanolamine and an unknown lipid as the major polar lipids, and menaquinone MK-6 as the major respiratory quinone. The DNA G+C contents were 32.8 and 35.0 mol% for X15M-6T and X15M-8T, respectively. Phylogenetic trees based on 16S rRNA gene sequences showed that both strains belonged to the genus Psychroflexus and formed a separate lineage. In addition, strains X15M-6T and X15M-8T shared 96.8 % 16S rRNA gene sequence similarity and showed highest similarities to members of the genus Psychroflexus (92.7-93.5 and 91.8-93.1 %, respectively). Based on the above data, it is concluded that strains X15M-6T and X15M-8T represent two novel species of the genus Psychroflexus, for which the names Psychroflexus salis sp. nov. (type strain X15M-6T = CGMCC 1.12925T = JCM 30615T) and Psychroflexus planctonicus sp. nov. (type strain X15M-8T = CGMCC 1.12931T = JCM 30616T) are proposed.