Halorubrum yunnanense sp. nov., isolated from a subterranean salt mine

Abstract

Two halophilic archaeal strains, Q85T and Q86, were isolated from a subterranean salt mine in Yunnan, China. Cells were rod-shaped, Gram-stain-negative and motile. Colonies were red, smooth, convex and round (1.0–2.0 mm in diameter). The orthologous 16S rRNA and rpoB′ gene sequences of these two strains were almost identical (99.5 and 99.7 % similarities). Their closest relatives were Halorubrum kocurii BG-1T (98.0–98.1 % 16S rRNA gene sequence similarity), Halorubrum aidingense 31-hongT (97.6–97.7 %) and Halorubrum lipolyticum 9-3T (97.5–97.6 %). The level of DNA–DNA relatedness between strains Q85T and Q86 was 90 %, while that between Q85T and other related Halorubrum strains was less than 30 % (29 % for H. kocurii BG-1T, 25 % for H. aidingense 31-hongT and 22 % for H. lipolyticum 9-3T). Optimal growth of the two novel strains was observed with 20 % (w/v) NaCl and at 42–45 °C under aerobic conditions, with a slight difference in optimum Mg2+ concentration (0.7 M for Q85T, 0.5 M for Q86) and a notable difference in optimum pH (pH 7.5 for Q85T, pH 6.6 for Q86). Anaerobic growth occurred with nitrate, but not with l-arginine or DMSO. The major polar lipids of the two strains were identical, including phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate and sulfated diglycosyl diether, which are the major lipids of the genus Halorubrum. The G+C contents of strains Q85T and Q86 were 66.3 and 66.8 %, respectively. Based on the phenotypic, chemotaxonomic and phylogenetic properties of strains Q85T and Q86, a novel species, Halorubrum yunnanense sp. nov., is proposed. The type strain is Q85T ( = CGMCC 1.15057T = JCM 30665T).