Halobaculum roseum sp nov., isolated from underground salt deposits

Two extremely halophilic archaea, strains D90(T) and D93, were isolated from underground salt deposits of Yunnan salt mine, China. Both strains were pleomorphic or short rods, non-motile, Gram-negative and required 1.7 M NaCl for growth, with optimum at 3.4 M. Mg2+ was not required for growth. Multiple copies of the 16S rRNA gene were obtained for both strains. Sequence similarity analysis of 16S rRNA genes revealed that strains D90(T) and D93 were closely related to Halobaculum magnesiiphilum MGY-184(T) and Halobaculum gomorrense DSM 9297(T) with the sequence similarity between 96.2-98.1 %. The sequence similarity of the rpoB' gene between strain D90(T) and Halobaculum gomorrense JCM 9908(T) was 94.1 %. The DNA G+C contents of strains D90(T) and D93 were 65.9 and 67.6 mol%, respectively. The major polar lipids of both strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and glycolipid. The DNA-DNA relatedness value between strains D90(T) and D93 was 90.1 +/- 0.5 %, while that between strain D90(T) and Halobaculum gomorrense JCM 9908(T) was 30.0 +/- 0.7 %. The comparison of physiological and biochemical characteristics, including the requirements of NaCl, Mg2+, pH, etc., differentiated strains D90(T) and D93 from Halobaculum magnesiiphilum MGY-184(T) and Halobaculum gomorrense JCM 9908(T). Therefore, strains D90(T) and D93 represent a novel species of the genus Halobaculum, for which the name Halobaculum roseum sp. nov. is proposed. The type strain is D90(T) (= CGMCC 1.15501(T) = JCM 31273(T)).