Proposal that the arsenite-oxidizing organisms Thiomonas cuprina and 'Thiomonas arsenivorans' be reclassified as strains of Thiomonas delicata, and emended description of Thiomonas delicata.

The three As(III)-oxidizing members of the class Betaproteobacteria Thiomonas delicata, Thiomonas cuprina and 'Thiomonas arsenivorans' were isolated from mining sites in geographically distinct areas, namely Japan, Germany and France, respectively. They are all able to oxidize As(III) but only 'T. arsenivorans' and T. cuprina show efficient autotrophic growth with As(III) and are able to grow on a sole carbon source. These two organisms are also motile, whereas T. delicata is not. Only T. cuprina can grow autotrophically on chalcopyrite. The three strains share >99% gene sequence similarity with each other based on their 16S rRNA genes and 16S-23S ITS regions. DNA-DNA hybridization results are above, or close to, the threshold value of 70% recommended for the definition of bacterial species. The three taxa show very similar fatty acid profiles with differences only in five minor fatty acid components. They possess phylogenetic and chemotaxonomic similarities supporting the reclassification of these taxa as a single species. We propose that 'T. arsenivorans' and T. cuprina be reassigned as strains of T. delicata (type strain DSM 17897(T)).