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

Strain MD5(T), 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 MD5(T) is related to Tropicibacter naphthalenivorans C02(T), Phaeobacter inhibens T5(T), P. gallaeciensis BS107(T) and P. daeponensis TF-218(T), with 96.9, 96.2, 96.1 and 96.1% sequence similarity, respectively. Phylogenetic analyses also showed that strain MD5(T) forms a stable clade only with naphthalenivorans C02(T). Strain MD5(T) 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 beta-galactosidase and urease activities and aesculin hydrolysis. Enzyme activities displayed in the API ZYM strip were alkaline phosphatase, leucine arylamidase, acid phosphatase and alpha-glucosidase. Major cellular fatty acids were summed feature 8 (C-18:1 omega 7c and/or C-18:1 omega 6c; 70.9%) and C-16:0 (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 MD5(T) (=CECT 7557(T) =KCTC 23350(T)).