Silicibacter pomeroyi sp. nov. and Roseovarius nubinhibens sp. nov., dimethylsulfoniopropionate-demethylating bacteria from marine environments

Three Gram-negative, rod-shaped, aerobic bacteria that were capable of degrading dimethylsulfoniopropionate (DMSP) were isolated from marine waters. These isolates (DSS-3(T), DSS-10 and ISM(T)) exhibited the ability to demethylate and cleave DMSP, as well as to degrade other sulfur compounds related to DMSP that are cycled in marine environments. Intracellular poly-beta-hydroxybutyrate inclusions, surface blebs and one polar, complex flagellum that rotated exclusively in the clockwise direction were observed for DSS-3(T). The outer membrane of ISM(T) was separated from the cytoplasm at the poles in a toga-like morphology. The primary fatty acid in both strains was C(18 : 1)omega7c. DNA G+C contents for the isolates were 68.0+/-0.1, 68.1+/-0.1 and 66.0+/-0.2 mol% for DSS-3(T), DSS-10 and ISM(T), respectively. 16S rRNA gene sequence analyses placed these organisms within the Roseobacter lineage of the alpha-PROTEOBACTERIA: Closely related species were Silicibacter lacuscaerulensis and Ruegeria atlantica (DSS-3(T) and DSS-10) and Roseovarius tolerans (ISM(T)). Neither DSS-3(T) nor ISM(T) exhibited 16S rRNA similarity >97 % or DNA-DNA hybridization values >45 % to their nearest described relatives. Genotypic and phenotypic analyses support the creation of two novel species: Silicibacter pomeroyi sp. nov. with strain DSS-3(T) (=ATCC 700808(T)=DSM 15171(T)) as the type strain, and Roseovarius nubinhibens sp. nov. with strain ISM(T) (=ATCC BAA-591(T)=DSM 15170(T)) as the type strain.