Halobellus captivus sp. nov., an extremely halophilic archaeon isolated from a subterranean salt mine.

An extremely halophilic archaeon, strain ZY21, was isolated from a subterranean rock salt sample in Yunnan, China. Colonies of strain ZY21 on nutrient-rich agar plates are orange, wet and transparent. Cells are pleomorphic, motile, Gram-stain negative and lyse in distilled water. Cells can grow at 20-55 °C (optimum 42 °C), in the presence of 15-30% (w/v) NaCl (optimum 18-20%) and at pH 6.0-9.5 (optimum 7.5). Mg is required for growth (optimum 0.3 M). The major polar lipids of strain ZY21 are phosphatidylglycerol, phosphatidylglycerol sulfate and phosphatidylglycerol phosphate methyl ester, sulfated mannosyl-glucosyl-glycerol diether-1 and seven unidentified glycolipids. Sequence similarity searches with the 16S rRNA gene and rpoB' gene showed that strain ZY21 is closely related to Halobellus rufus CBA1103 (sequence similarities: 97.5% for 16S rRNA gene and 93.3% for rpoB' gene). The DNA G+C content of strain ZY21 was determined to be 63.0 mol% based on the draft genome sequence. Genome-based sequence similarity analysis showed that the values of the ANI, AAI, and DDH were far below the boundary for delineation of new species. Phenotypic, chemotaxonomic characteristics and phylogenetic properties suggest that strain ZY21 represents a novel species in the genus Halobellus, for which the name Halobellus captivus sp. nov. is proposed. The type strain is ZY21 (= CGMCC 1.16343 = NBRC 113439).