Transfer of Acidiphilium facilis and Acidiphilium aminolytica to the Genus Acidocella gen. nov., and Emendation of the Genus Acidiphilium

Abstract

Summary Phylogenetic relationships among members of the genus Acidiphilium and related genera were elucidated by studying 16S rRNA gene sequence information. Approximately 1.5 kbp fragments of 16S rDNAs from the test organisms were amplified by the polymerase chain reaction and sequenced directly by the combined method consisting of cycle sequencing and automated fluorescence detection. Sequence comparisons and evolutionary distance analyses with the sequence from some reference species showed that all members of the genus Acidiphilium formed a cluster within the alpha- I subclass of the Proteobacteria, with Acidomonas methanolica, Acetobacter aceti, and Rhodopila globiformis as the nearest phylogenetic neighbors. The Acidiphilium cluster was divided into two subclusters whose monophyly was supported by high levels of bootstrap confidence: one included A. facilis and A. aminolytica, and the other consisted of all other Acidiphilium species. The levels of sequence similarity between species of the different subclusters were less than 94.2%. The A. facilis-A. aminolytica group is also distinguishable from the other group in a number of phenotypic and chemotaxonomic characteristics. Thus we propose to transfer A. aminolytica and A. facilis to a new genus, Acidocella gen. nov., with Acidocella facilis as the type species. Following this proposal, the description of the genus Acidiphilium was emended.