Two novel acidothermophilic archaea, strains Ric-AT and Ric-F, were isolated from muddy water samples of a sulfuric hot spring located in Tengchong County, Yunnan Province, PR China. The strains were aerobic and facultatively chemolithoautotrophic. Both strains could oxidize S0 and K2S4O6 for autotrophic growth, and could use organic materials for heterotrophic growth. Growth was observed at 55–75 °C and pH 1.5–6.5. The strains could oxidize metal sulfide ores, showing their potential in bioleaching. The DNA G+C contents of strains Ric-AT and Ric-F were 41.8 and 41.6 mol%, respectively. Analysis of 16S rRNA gene sequences showed that the two strains shared 99.8 % sequence similarity to each other, but <97 % to other known species of the genus Metallosphaera . DNA–DNA hybridization indicated that the isolates were different strains of a novel species of the genus Metallosphaera . Strains Ric-AT and Ric-F also shared a number of physiological and biochemical characteristics that distinguished them from recognized species of the genus Metallosphaera . On the basis of phenotypic, chemotaxonomic and phylogenetic comparisons with their closest relatives, it was concluded that strains Ric-AT and Ric-F represent a novel species of the genus Metallosphaera , for which the name Metallosphaera tengchongensis sp. nov. is proposed. The type strain is Ric-AT ( = NBRC 109472T = CGMCC 1.12287T).
Two halophilic archaeal strains, TRM20010T and TRM20345T, 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 TRM20010T and TRM20345T 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 Mg2+ 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 TRM20010T and TRM20345T 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 TRM20010T and TRM20345T were 63.9 and 63.8 mol%, respectively. The DNA–DNA hybridization value between strain TRM20010T and strain TRM20345T was 42.8 %. The phenotypic, chemotaxonomic and phylogenetic properties suggested that strains TRM20010T and TRM20345T represent two novel species in a new genus within the family Halobacteriaceae , for which the names Natribaculum breve gen. nov., sp. nov. (type strain TRM20010T = CCTCC AB2013112T = NRRL B-59996T) and Natribaculum longum sp. nov. (type strain TRM20345T = CCTCC AB2013113T = NRRL B-59997T) are proposed.