A novel thermophilic and lithoautotrophic sulfate-reducing archaeon was isolated from black rust formed on the steel surface of a borehole observatory (CORK 1026B) retrieved during IODP Expedition 301 on the eastern flank of Juan de Fuca Ridge, eastern Pacific Ocean. Cells of the strain were lobe-shaped or triangular. The optimum temperature, pH and NaCl concentration for growth were 75 °C, pH 7 and 2 % (w/v), respectively. The isolate was strictly anaerobic, growing lithoautotrophically on H2 and CO2 using sulfate, sulfite or thiosulfate as electron acceptors. Lactate and pyruvate could serve as alternative energy and carbon sources. The G+C content of the genomic DNA was 42 mol%. Phylogenetic analyses of the 16S rRNA gene indicated that the isolate was closely related to members of the family Archaeoglobaceae, with sequence similarities of 90.3–94.4 %. Physiological and molecular properties showed that the isolate represents a novel species of the genus Archaeoglobus. The name Archaeoglobus sulfaticallidus sp. nov. is proposed; the type strain is PM70-1T (=DSM 19444T=JCM 14716T).
A novel extremely halophilic archaeon, strain 194-10T, was isolated from a solar salt sample imported into Japan from the Philippines. Strain 194-10T was pleomorphic, neutrophilic and mesophilic and required at least 10 % (w/v) NaCl but no MgSO4 . 7H2O for growth; it exhibited optimal growth at 15 % (w/v) NaCl and 60 mM MgSO4 . 7H2O. Strain 194-10T grew at 20–45 °C (optimum, 30 °C) and pH 6.0–9.0 (optimum, pH 6.5–7.0). The G+C content of its DNA was 59.8 mol%. 16S rRNA gene sequence analysis revealed closest proximity to Halostagnicola larsenii XH-48T (98.5 % similarity), the sole representative of the genus Halostagnicola. Polar lipid analysis revealed that strain 194-10T contained phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester (the latter derived from both C20C20 and C20C25 archaeol) and several unidentified glycolipids. The results of DNA–DNA hybridization (20.7 % relatedness between Hst. larsenii JCM 13463T and strain 194-10T) and physiological and biochemical characteristics allowed differentiation of strain 194-10T from Hst. larsenii XH-48T. Therefore, strain 194-10T represents a novel species of the genus Halostagnicola, for which the name Halostagnicola kamekurae sp. nov. is proposed, with the type strain 194-10T (=DSM 22427T =JCM 16110T =CECT 7536T).
A novel hydrogenotrophic methanogen, designated strain MRE50T, was isolated from a methanogenic consortium, which was originally established from an Italian rice field soil. Cells were non-motile rods, 1.3–2.8 μm long and 0.4–0.7 μm wide. Coccoid cells were also observed in cultures at the late-exponential phase of growth. Strain MRE50T grew at 37–55 °C (optimally at 45 °C), at pH 6–7.8 (optimally at pH 7.0) and in the presence of 0–20 g NaCl l−1. The isolate utilized H2/CO2 and formate for growth and methane production. Phylogenetic analyses of the 16S rRNA gene and the methanogen-specific marker gene mcrA showed that strain MRE50T is affiliated with the order Methanocellales, previously known as uncultured archaeal group Rice Cluster I. Based on both 16S rRNA gene and mcrA gene sequences, strain MRE50T was related most closely to Methanocella paludicola SANAET. Levels of sequence similarity were 92.5 and 86.1 %, respectively, indicating that strains MRE50T and Methanocella paludicola SANAET represent different species within the genus Methanocella. In addition, although these strains shared phenotypic properties including cell morphology and substrate utilization, they differed with respect to susceptibility to antibiotics, and temperature and NaCl ranges for growth. Given the phenotypic differences and the distinct phylogenetic placement of the new isolate relative to the type species of the genus Methanocella, strain MRE50T is considered to represent a novel species of the genus Methanocella, for which the name Methanocella arvoryzae sp. nov. is proposed. The type strain is MRE50T (=NBRC 105507T =DSM 22066T).