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

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Abstract
Three Gram-negative, rod-shaped, aerobic bacteria that were capable of degrading dimethylsulfoniopropionate (DMSP) were isolated from marine waters. These isolates (DSS-3T, DSS-10 and ISMT) 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-β-hydroxybutyrate inclusions, surface blebs and one polar, complex flagellum that rotated exclusively in the clockwise direction were observed for DSS-3T. The outer membrane of ISMT was separated from the cytoplasm at the poles in a toga-like morphology. The primary fatty acid in both strains was C18 : 1ω7c. DNA G+C contents for the isolates were 68·0±0·1, 68·1±0·1 and 66·0±0·2 mol% for DSS-3T, DSS-10 and ISMT, respectively. 16S rRNA gene sequence analyses placed these organisms within the Roseobacter lineage of the α-Proteobacteria. Closely related species were Silicibacter lacuscaerulensis and Ruegeria atlantica (DSS-3T and DSS-10) and Roseovarius tolerans (ISMT). Neither DSS-3T nor ISMT 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-3T (=ATCC 700808T=DSM 15171T) as the type strain, and Roseovarius nubinhibens sp. nov. with strain ISMT (=ATCC BAA-591T=DSM 15170T) as the type strain.