Tepidiphilus margaritifer gen. nov., sp nov., isolated from a thermophilic aerobic digester

A moderately thermophilic bacterium is described, strain N2-21 4(T), that was isolated from an enrichment culture, growing on caprolactone, obtained from a sample from a water-treatment sludge aerobic digester operating at temperatures around 60 degreesC. The organism was aerobic, Gram-negative, oxidase- and catalase-positive, with a polar flagellum, and capable of growth at temperatures as high as 61 degreesC. The major fatty acids of strain N2-21 4(T) were C-16 : 0, C-18 : 1 and cyclo-C-19 : 0. The phylogenetic relationships of the strain, derived from 16S rRNA gene sequence comparisons, demonstrated it to be a member of the beta-subclass of the Proteobacteria. The highest 16S rDNA sequence similarity of isolate N2-21 4(T) was to Azoarcus buckelii (91.9%), Thauera aromatica (92 %) and Hydrogenophilus thermoluteolus (92.7 %). On the basis of phylogenetic analyses and physiological and chemotaxonomic characteristics, it is proposed that isolate N2-21 4(T) (= DSM 15129(T) = LMG 21637(T)) represents a new genus and species, Tepidiphilus margaritifer gen. nov., sp. nov.