Caldimonas manganoxidans gen. nov., sp. nov., a poly(3-hydroxybutyrate)-degrading, manganese-oxidizing thermophile.

A poly(3-hydroxybutyrate) (PHB)-degrading, gram-negative, aerobic bacterium, strain HS(T), was isolated from a hot spring and chemotaxonomically and phylogenetically characterized. The oxidase-positive, weakly catalase-positive, non-pigmented cells (0.6 x 2.6 microm) exhibited a single polar flagellum and accumulated PHB granules. Strain HS(T) was capable of manganese oxidation. Highest growth rate was attained at 50 degrees C. The optimum pH for growth was 7-8. The major respiratory quinone was ubiquinone-8 and major cellular fatty acids were C16:0, C16:1 and C18:1. The G+C content of the DNA was 66.2 mol%. Comparative 16S rDNA analysis indicated that strain HS(T) is related to the Rubrivivax subgroup and the family Comamonadaceae. The nearest phylogenetic relatives were Ideonella dechloratans (92.1% similarity), Leptothrix discophora (93.6%), Roseateles depolymerans (92.4%) and Rubrivivax gelatinosus (92.2%). On the basis of its phylogenetic and phenotypic properties, it is proposed that this isolate be designated Caldimonas manganoxidans gen. nov., sp. nov.; the type strain is HS(T) (= JCM 10698T = IFO 16448T = ATCC BAA-369T).