Ruegeria denitrificans sp nov., a marine bacterium in the family Rhodobacteraceae with the potential ability for cyanophycin synthesis

Strain CECT 5091 Tau, an aerobic, marine, Gram-reaction- and Gram-stain-negative, chemoheterotrophic bacterium was isolated from oysters harvested off the Spanish Mediterranean coast. Analysis of the 16S rRNA gene sequence placed the strain within the genus Ruegeria, in the family Rhodobacteraceae, with 16S rRNA gene similarities of 98.7, 98.7 and 98.4% to Ruegeria conchae, Ruegeria atlantica and Ruegeria arenilitoris, respectively Average nucleotide identities (ANI) and in silico DNA-DNA hybridization (DDH) were determined, comparing the genome sequence of CECT 5091(Tau) with those of the type strains of 12 species of the genus Ruegeria: the values obtained were always below the thresholds (95-96 % ANI, 70% in silico DDH) used to define genomic species, proving that CECT 5091(Tau) represents a novel species of the genus Ruegeria. The strain was slightly halophilie and mesophilic, with optimum growth at 26 degrees C, pH 7.0 and 3% salinity, it required sodium and magnesium ions for growth and was able to reduce nitrate to dinitrogen. Carbon sources for growth include some carbohydrates (D-ribose, D-glucose, L-rhamnose, N-acetyl-D-glucosamine) and multiple organic acids and amino acids. The major cellular fatty acid was summed feature 8 (C-18:1 omega 7c and/or C-18:1 omega 6c), representing 70% of the total fatty acids. Carbon monoxide oxidation, cyanophycin synthetic ability and phosphatidylglycerol, diphosphatidylglycerol and phosphatidylcholine production are predicted from genome annotation, while bacteriochlorophyll a production was absent. The DNA G+C content of the genome was 56.7 mol%. We propose the name Ruegeria denitrificans sp. nov. and strain CECT 5091(Tau) (=50M10(Tau)=LMG 29896(Tau)) as the type strain for the novel species.