Natribaculum breve gen. nov., sp. nov. and Natribaculum longum sp. nov., halophilic archaea isolated from saline soil.

Two halophilic archaeal strains, TRM20010(T) and TRM20345(T), were isolated from saline soil of the Lop Nur region in Xinjiang, north-west China. Cells from the two strains were pleomorphic rods, stained Gram-negative and produced red-pigmented colonies. Strains TRM20010(T) and TRM20345(T) were able to grow at 30-62 °C (optimum 37 °C), 0.9-5.1 M NaCl (optimum 2.6 and 3.4 M, respectively) and pH 6.0-10.0 (optimum pH 7.0-7.5) and neither strain required Mg(2+) for growth. The major polar lipids of the two strains were phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), two glycolipids chromatographically identical to galactosyl mannosyl glucosyl diether (TGD-1) and disulfated mannosyl glucosyl diether (S2-DGD). Phylogenetic analysis based on 16S rRNA and rpoB' genes revealed that strains TRM20010(T) and TRM20345(T) clustered together and formed a distinct clade separated from the related genera Halovivax, Haloterrigena, Halostagnicola, Natronolimnobius and Natrinema. The DNA G+C contents of strains TRM20010(T) and TRM20345(T) were 63.9 and 63.8 mol%, respectively. The DNA-DNA hybridization value between strain TRM20010(T) and strain TRM20345(T) was 42.8 %. The phenotypic, chemotaxonomic and phylogenetic properties suggested that strains TRM20010(T) and TRM20345(T) represent two novel species in a new genus within the family Halobacteriaceae, for which the names Natribaculum breve gen. nov., sp. nov. (type strain TRM20010(T) = CCTCC AB2013112(T) = NRRL B-59996(T)) and Natribaculum longum sp. nov. (type strain TRM20345(T) = CCTCC AB2013113(T) = NRRL B-59997(T)) are proposed.