A hyperthermophilic, anaerobic, piezophilic archaeon (strain DY20341T) was isolated from a sediment sample collected from an East Pacific Ocean hydrothermal field (1° 37′ S 102° 45′ W) at a depth of 2737 m. The cells were irregular cocci, 0.8–1.5 µm in diameter. Growth was observed between 50 and 90 °C (optimum 80 °C), pH 5.0 and 8.0 (optimum pH 7.0), 1 % and 7 % (w/v) sea salts (Sigma, optimum 3 %), 1 % and 4 % (w/v) NaCl (optimum 3 %) and 0.1 and 80 MPa (optimum 30 MPa). The minimum doubling time was 66 min at 30 MPa and 80 °C. The isolate was an obligate chemoorganoheterotroph, capable of utilizing complex organic compounds and organic acids including yeast extract, peptone, tryptone, casein, starch, Casamino acids, citrate, lactate, acetate, fumarate, propanoate and pyruvate for growth. It was strictly anaerobic and facultatively dependent on elemental sulfur or sulfate as electron acceptors, but did not reduce sulfite, thiosulfate, Fe(III) or nitrate. The presence of elemental sulfur enhanced growth. The G+C content of the genomic DNA was 43.6±1 mol%. 16S rRNA gene sequence analysis revealed that the closest relative of the isolated organism was Palaeococcus ferrophilus DMJT (95.7 % 16S rRNA gene similarity). On the basis of its physiological properties and phylogenetic analyses, the isolate is considered to represent a novel species, for which the name Palaeococcus pacificus sp. nov. is proposed. The type strain is strain DY20341T ( = JCM 17873T = DSM 24777T).
Two extremely halophilic archaea, designated YIM 94188T and YIM 94189, were isolated from Qijiaojing lake in Xinjiang province, north-west China and subjected to taxonomic characterization using a polyphasic approach. The cells of the two strains were coccoid, non-motile and Gram-stain-negative. Colonies were pink–white-pigmented and aerobic. Growth occurred at 10–30 % (w/v) NaCl, 20–55 °C and pH 6.0–8.0 (optimum: 20–25 % NaCl, 37–42 °C, pH 6.5–7.0). Magnesium was necessary for growth in the range of 0.2–1.2 M. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that the two strains belonged to the genus Halopelagius showing 98.5 % sequence similarity to the closest phylogenetic neighbour, Halopelagius inordinatus RO5-2T. In addition, the DNA–DNA hybridization values of strains YIM 94188T and YIM 94189 to Halopelagius inordinatus RO5-2T were 35.7 % and 37.7 %, respectively. Polar lipid analyses revealed that the two strains contained phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), sulfated mannosyl glucosyl diether (S-DGD-1) and mannosyl glucosyl diether (DGD-1). The DNA G+C contents of strains YIM 94188T and YIM 94189 were 66.3 mol% and 64.6 mol%, respectively. On the basis of physiological and chemotaxonomic data, and phylogenetic analysis, strains YIM 94188T and YIM 94189 were classified as representing a novel species in the genus Halopelagius . The name Halopelagius fulvigenes sp. nov. is proposed, with YIM 94188T ( = CCTCC AB 2010456T = JCM 17506T) as the type strain.