Roseovarius albus sp. nov., a new Alphaproteobacterium isolated from the Mediterranean Sea

Strain 4SM10^T, an aerobic marine, Gram-negative, heterotrophic and non pigmented bacterium isolated from seawater from Vinaroz in Castellón, Spain, was characterized using a polyphasic approach. Analysis of the 16S rRNA gene sequence placed the strain within the Roseobacter clade in the family Rhodobacteraceae. Phylogenetic analyses also showed that strain 4SM10^T forms a stable clade with species of the genus Roseovarius, being related to Roseovarius nubinhibens ISM^T and Roseovarius aestuarii SMK-122^T at 97.5 and 97.4 % 16S rRNA sequence similarity, respectively. Average Nucleotide Identity (ANI) values, determined as a measure of overall genomic resemblance, confirmed that strain 4SM10^T does not belong to the same species as R. aestuarii CECT 7745^T and Roseovarius nubinhibens CECT 7750^T displaying ANI values well below the 95 % boundary for genomic species. Strain 4SM10^T requires Na⁺ plus a divalent cation (either Mg²⁺ or Ca²⁺) to grow, reduces nitrate to nitrite and uses a large number of amino acids and organic acids (but no carbohydrates) as sole carbon sources. Enzymatic activities displayed in API ZYM tests are alkaline phosphatase, leucine arylamidase and acid phosphatase. The major cellular fatty acids were identified as C_18:1 ω7c and/or C_18:1 ω6c (67.1 %). The DNA G+C content was determined to be 54.27 mol%. Based on the genotypic and phenotypic data obtained, the name Roseovarius albus sp. nov. is proposed for this novel taxon, with the type strain 4SM10^T (=CECT 7450^T = KCTC 22653^T).