Extremely halophilic archaea were cultivated from smooth and pustular microbial mats collected from Hamelin Pool, Shark Bay, Western Australia. On the basis of morphology, two phenotypes were present and 16S rRNA gene sequence analysis indicated that all strains were most closely related to members of the genus Haloferax (98.1–99.4 % similarity). One representative strain from each phenotype was selected for further taxonomic characterization. Strain SA5T, isolated from the smooth mat, formed small (∼1 mm diameter), red, translucent colonies on agar medium and strain PA12T, isolated from the pustular mat, formed large (3–5 mm diameter), pink, mucoid, domed colonies. Both strains grew in media with 1.7–5.1 M NaCl, required at least 0.2 M Mg2+ for growth and had pH optima of 7.4. The 16S rRNA gene similarity between strains SA5T and PA12T was 97.1 %. Physiological properties, G+C content and polar lipid composition supported placement of both strains in the genus Haloferax. Phenotypic analysis indicated that the two strains were distinct from each other and from all other members of the genus. This was confirmed by the low DNA–DNA relatedness between strains SA5T and PA12T (18–30 %) and between both strains and all other recognized Haloferax species. Two novel species of the genus Haloferax are proposed to accommodate these novel isolates, Haloferax elongans sp. nov. (type strain SA5T=JCM 14791T=ATCC BAA-1513T=UNSW 104100T) and Haloferax mucosum sp. nov. (type strain PA12T=JCM 14792T=ATCC BAA-1512T=UNSW 104200T).
A novel thermophilic, strictly anaerobic archaeon, designated strain Arc51T, was isolated from a rock sample collected from a deep-sea hydrothermal field in Suiyo Seamount, Izu-Bonin Arc, western Pacific Ocean. Cells of the isolate were irregular cocci with single flagella and exhibited blue–green fluorescence at 436 nm. The optimum temperature, pH and NaCl concentration for growth were 70 °C, pH 6.5 and 3 % (w/v), respectively. Strain Arc51T could grow on thiosulfate or sulfite as an electron acceptor in the presence of hydrogen. This strain required acetate as a carbon source for its growth, suggesting that the reductive acetyl CoA pathway for CO2 fixation was incomplete. In addition, coenzyme M (2-mercaptoethanesulfonic acid), which is a known methyl carrier in methanogenesis, was also a requirement for growth of the strain. Analysis of the 16S rRNA gene sequence revealed that the isolate was similar to members of the genus Archaeoglobus, with sequence similarities of 93.6–97.2 %; the closest relative was Archaeoglobus veneficus. Phylogenetic analyses of the dsrAB and apsA genes, encoding the alpha and beta subunits of dissimilatory sulfite reductase and the alpha subunit of adenosine-5′-phosphosulfate reductase, respectively, produced results similar to those inferred from comparisons based on the 16S rRNA gene sequence. On the basis of phenotypic and phylogenetic data, strain Arc51T represents a novel species of the genus Archaeoglobus, for which the name Archaeoglobus infectus sp. nov. is proposed. The type strain is Arc51T (=NBRC 100649T=DSM 18877T).
A novel halophilic archaeon, strain BZ256T, was isolated from Zodletone Spring, a sulfide- and sulfur-rich spring in south-western Oklahoma, USA. Cells were non-motile, non-flagellated cocci that divided along two axes, resulting in the formation of sarcina-like clusters. Strain BZ256T grew at salt concentrations ranging from 1.3 to 4.3 M NaCl, with optimum growth at approximately 3.4 M, and required at least 1 mM Mg2+ for growth. The pH range for growth was 5.0 to at least 8.5, and the temperature range for growth was 25–45 °C. The two diether phospholipids that are typical of members of the order Halobacteriales, namely phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester, were present in strain BZ256T, as were two glycolipids chromatographically identical to S-DGD-1 and DGD-1. The 16S rRNA gene sequence of strain BZ256T showed 96.8 % similarity to that of the type strain of Halogeometricum borinquense, the closest recognized species within the order Halobacteriales. The DNA G+C content of strain BZ256T was 65.4 mol%. Microscopic, physiological, biochemical and phylogenetic comparisons between strain BZ256T and recognized genera of extremely halophilic archaea suggest that this strain represents a member of a novel genus and species within the family Halobacteriaceae, for which the name Halosarcina pallida gen. nov., sp. nov. is proposed. The type strain of Halosarcina pallida is BZ256T (=KCTC 4017T =JCM 14848T).
A novel mesophilic, hydrogenotrophic methanogen, strain SANAET, was isolated from an anaerobic, propionate-degrading enrichment culture, which was originally established from rice paddy soil. The cells were non-motile, Gram-negative and rod-shaped (1.8–2.4 μm long by 0.3–0.6 μm wide). Growth of strain SANAET was observed at 25–40 °C, with an optimum temperature range for growth of 35–37 °C. The pH range for growth was 6.5–7.8, with an optimum at pH 7.0. The salinity range for growth was 0–1 g NaCl l−1 (0–17 mM). The isolate was able to utilize H2/CO2 and formate for growth and methane production. The G+C content of the genomic DNA was 56.6 mol%. Based on comparative 16S rRNA gene sequence analysis, strain SANAET was affiliated with a clone lineage of the Archaea, Rice Cluster I (RC-I), placing it between the orders Methanosarcinales and Methanomicrobiales within the class ‘Methanomicrobia’. 16S rRNA gene sequence similarities between strain SANAET and members of Methanosarcinales were in the range 80.0–82.8 %, and those between the strain and members of Methanomicrobiales ranged from 77.5 to 82.4 %. In addition to 16S rRNA gene analysis, sequence analysis of the mcrA gene (encoding the α subunit of methyl-coenzyme M reductase, a key enzyme in the methane production pathway) also showed that strain SANAET was affiliated with the RC-I lineage. Here, we propose the name Methanocella paludicola gen. nov., sp. nov. for the isolate, the first of the RC-I lineage. The type strain is SANAET (=JCM 13418T=NBRC 101707T=DSM 17711T). In addition, we also propose the status of order for the RC-I lineage, for which we propose the name Methanocellales ord. nov.