Acidiphilium iwatense sp nov., isolated from an acid mine drainage treatment plant, and emendation of the genus Acidiphilium

Several strains of aerobic, acidophilic, chemo-organotrophic bacteria belonging to the genus Acidiphilium were isolated from an acid mine drainage (AMD) (pH 2.2) treatment plant. 16S rRNA gene sequence comparisons showed that most of the novel isolates formed a phylogenetically coherent group (designated Group la) distinguishable from any of the previously established species of the genus Acidiphilium at <98% similarity. This was supported by genomic DNA-DNA hybridization assays. The Group la isolates were characterized phenotypically by an oval cell morphology, non-motility, growth in the range pH 2.0-5.5 (optimum pH 3.5), lack of photosynthetic pigment and the presence of C-19:0 cyclo omega 8c as the main component of the cellular fatty acids and ubiquinone-10 as the major quinone. On the basis of these data, the name Acidiphilium iwatense sp. nov. is proposed to accommodate the Group la isolates, and the description of the genus Acidiphilium is emended. The type strain of Acidiphilium iwatense sp. nov. is MS8(T) (=NBRC 107608(T)=KCTC 23505(T)).