Tropicibacter multivorans sp. nov., an aerobic alphaproteobacterium isolated from surface seawater.

Strain MD5T, an aerobic marine alphaproteobacterium, was isolated from Mediterranean seawater at Malvarrosa beach, Valencia, Spain. The strain was characterized in a polyphasic study and was placed phylogenetically within the Roseobacter clade in the family Rhodobacteraceae. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain MD5T is related to Tropicibacter naphthalenivorans C02T, Phaeobacter inhibens T5T, P. gallaeciensis BS107T and P. daeponensis TF-218T, with 96.9, 96.2, 96.1 and 96.1 % sequence similarity, respectively. Phylogenetic analyses also showed that strain MD5T forms a stable clade only with T. naphthalenivorans C02T. Strain MD5T requires Na+ plus a divalent cation (either Mg2+ or Ca2+) to grow, does not reduce nitrate to nitrite and uses a large number of carbohydrates as sole carbon sources. It is positive for β-galactosidase and urease activities and aesculin hydrolysis. Enzyme activities displayed in the API ZYM strip were alkaline phosphatase, leucine arylamidase, acid phosphatase and α-glucosidase. Major cellular fatty acids were summed feature 8 (C18:1ω7c and/or C18:1ω6c; 70.9 %) and C16:0 (8.2 %). The results of physiological and biochemical tests allowed clear phenotypic differentiation of this isolate from the only described species of the genus Tropicibacter. It is evident from the genotypic and phenotypic data obtained that the strain should be classified in a novel species in the genus Tropicibacter. The name Tropicibacter multivorans sp. nov. is proposed, with the type strain MD5T (=CECT 7557T=KCTC 23350T).