Metallosphaera javensis sp. nov., a novel species of thermoacidophilic archaea, isolated from a volcanic area.

A novel thermoacidophilic archeaon, strain J1 ^T (=DSM 112778 ^T ,=JCM 34702 ^T ), was isolated from a hot pool in a volcanic area of Java, Indonesia. Cells of the strain were irregular, motile cocci of 1.0-1.2 µm diameter. Aerobic, organoheterotrophic growth with casamino acids was observed at an optimum temperature of 70 °C in a range of 55-78 °C and at an optimum pH of 3 in a range of 1.5 to 5. Various organic compounds were utilized, including a greater variety of sugars than has been reported for growth of other species of the genus. Chemolithoautotrophic growth was observed with reduced sulphur compounds, including mineral sulphides. Ferric iron was reduced during anaerobic growth with elemental sulphur. Cellular lipids were calditoglycerocaldarchaeol and caldarchaeol with some derivates. The organism contained the respiratory quinone caldariellaquinone. On the basis of phylogenetic and chemotaxonomic comparison with its closest relatives, it was concluded that strain J1 ^T represents a novel species, for which the name Metallosphaera javensis is proposed. Low DNA-DNA relatedness values (16S rRNA gene <98.4%, average nucleotide identity (ANI) <80.1%) distinguished J1 ^T from other species of the genus Metallosphaera and the DNA G+C content of 47.3% is the highest among the known species of the genus.