Halorubrum trueperi sp nov., a halophilic archaeon isolated from a salt mine

A novel, extremely halophilic archaeon, strain Y73(T), was isolated from a salt mine in Yunnan, China. Colonies formed on solid medium were circular (2-3mm in diameter), smooth, orange, glistening and convex (similar to 1 mm in elevation). Cells were Gram-stain- negative, non-motile and pleomorphic. Mg2+ was required for growth (optimum at 0.05 M). Optimal growth was observed at 20% (w/v) NaCl, 42-45 degrees C and pH 7.5-8.5 under aerobic conditions. 16S rRNA gene sequence comparison showed that strain Y73(T) was closely related to Halorubrum halophilum B8(T) (similarity: 98.1 %), Halorubrum lipolyticum 9-3(T) (97.9 %) and Halorubrum saccharovorum JCM 8865(T) (97.6 %). Levels of rpoB' gene sequence similarity between strain Y73(T) and H. halophilum B8(T), H. lipolyticum 9-3(T) and H. saccharovorum JCM 8865(T) were 93.6, 93.8 and 94.7 %, respectively. DNA-DNA relatedness between strain Y73(T) and H. halophilum B8(T) was 38.7 +/- 0.5 %, while that between strain Y73(T) and H. saccharovorum JCM 8865(T) was 31.0 +/- 0.9%. The DNA G+C content of strain Y73(T) was 61.9 mol%. The major polar lipids of strain Y73(T) were phosphatidic acid, phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and phosphatidylglycerol sulfate as phospholipids, and sulfated diglycosyl diether-1 as glycolipid. The phenotypic, chemotaxonomic and phylogenetic properties suggest that strain Y73(T) represents a novel species, for which the name Halorubrum trueperi sp. nov is proposed. The type strain is Y73(T) (= CGMCC 1.15503(T) = JCM 31271(T)).