A novel acidothermophilic archaeon, strain Ar-4T, was isolated from a sulfuric hot spring in Tengchong, Yunnan, China. Cells of strain Ar-4T were Gram-staining-negative, irregular cocci and motile by means of flagella. Strain Ar-4T grew over a temperature range of 55–75 °C (optimum, 65 °C), a pH range of 2.5–5.5 (optimum, pH 3.5) and a NaCl concentration range of 0–1 % (w/v). The novel strain was aerobic and facultatively chemolithoautotrophic. The strain could extract metal ions from sulfidic ore. It was also able to oxidize reduced sulfur compounds. In addition, it was able to use heterogeneous organic materials for organotrophic growth. The main cellular lipids were calditoglycerocaldarchaeol (CGTE) and caldarchaeol (DGTE). The DNA G+C content of the strain was 40.2 mol%. Analysis of 16S rRNA gene sequences showed that strain Ar-4T was phylogenetically related to members of the genus Metallosphaera and had sequence similarities of 97.7 %, 97.0 % and 96.8 % with Metallosphaera hakonensis DSM 7519T, Metallosphaera sedula DSM 5348T and Metallosphaera prunae DSM 10039T, respectively. Strain Ar-4T showed DNA–DNA relatedness values of 47.5 %, 30.8 % and 29.1 % with M. hakonensis DSM 7519T, M. sedula DSM 5348T and M. prunae DSM 10039T, respectively. The differences in cell motility, the temperature and pH ranges for growth, the ability to utilize carbon sources, the DNA G+C content, and the low DNA–DNA relatedness values distinguished strain Ar-4T from recognized species of the genus Metallosphaera. On the basis of these results, it was concluded that strain Ar-4T represents a novel species of the genus Metallosphaera, for which the name Metallosphaera cuprina is proposed. The type strain is Ar-4T ( = JCM 15769T = CGMCC 1.7082T).
A methanogenic organism, designated strain HB-1T, from the domain Archaea was isolated from groundwater sampled from a subsurface Miocene formation located in Horonobe, Hokkaido, Japan. The strain grew on methanol, dimethylamine, trimethylamine, dimethylsulfide and acetate but not on monomethylamine, H2/CO2, formate, 2-propanol, 2-butanol or cyclopentanol. Cells were Gram-reaction-negative, non-motile, irregular cocci that were 1.4–2.9 µm in diameter and occurred singly or in pairs. The strain grew at 20–42 °C (optimum 37 °C), at pH 6.0–7.75 (optimum pH 7.0–7.25) and in 0–0.35 M NaCl (optimum 0.1 M). The G+C content of the genomic DNA was 41.4 mol%. 16S rRNA gene sequencing revealed that the strain was a member of the genus Methanosarcina but that it clearly differed from all recognized species of this genus (93.1–97.9 % sequence similarity). The phenotypic and phylogenetic features of strain HB-1T indicate that it represents a novel species of the genus Methanosarcina, for which the name Methanosarcina horonobensis sp. nov. is proposed. The type strain is HB-1T ( = DSM 21571T = JCM 15518T = NBRC 102577T).