Pelagibacterium halotolerans gen. nov., sp. nov. and Pelagibacterium luteolum sp. nov., novel members of the family hyphomicrobiaceae

Two Gram-negative, motile, aerobic bacterial strains, designated B2 ^T and 1_C16_27 ^T, were respectively isolated from a seawater sample collected from the East China Sea and a semi-coke sample from north-eastern Estonia. Their genetic, phenotypic and chemotaxonomic properties were studied. The isolates were short rods with polar flagella and were positive for catalase and oxidase activities. Q-10 was the predominant respiratory ubiquinone. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol and two unidentified glycolipids. The major fatty acids were nonadecanoic (C _{19: 0} cyclo), octadecanoic (C _{18: 0} and C _{18: 0} 3-OH), octadecenoic (C _{18: 1}) and hexadecanoic (C _{16: 0}) acids. The G+C content of the genomic DNA was 58.1-59.3 mol%. 16S rRNA gene sequence analysis revealed that the two isolates represent a distinct lineage within the family Hyphomicrobiaceae. The phylogenetically closest relatives were Cucumibacter (92.7-93.7% 16S rRNA gene sequence similarity), Devosia (92.9-94.4%) and Zhangella (91.7-92.1%). Differential phenotypic properties, together with phylogenetic and genetic distinctiveness, revealed that strains B2 ^T and 1_C16_27 ^T could be differentiated from each other and from members of the genera Cucumibacter, Devosia and Zhangella. Therefore, it is proposed that strains B2 ^T and 1_C16_27 ^T represent two novel species in a new genus, for which the names Pelagibacterium halotolerans gen. nov., sp. nov. (the type species; type strain B2 ^T 5CGMCC 1.7692 ^T 5JCM 15775 ^T) and Pelagibacterium luteolum sp. nov. (type strain 1_C16_27 ^T 5CGMCC 1.10267 ^T 5JCM 16552 ^T 5CELMS EEUT 1C1627 ^T) are proposed.