Pelagimonas varians gen. nov., sp. nov., isolated from the southern North Sea.

A heterotrophic, Gram-stain-negative, aerobic bacterium, designated strain SH4-1(T), was obtained from a seawater sample collected from the southern North Sea during a phytoplankton bloom. The 16S rRNA gene sequence comparison revealed affiliation to the Roseobacter clade (class Alphaproteobacteria) with Sulfitobacter marinus SW-265(T) as the most closely related characterized strain, showing 97.2 % 16S rRNA gene sequence similarity. Calculation of phylogenetic trees based on 16S rRNA gene sequences indicated, however, that members of the genus Roseobacter, Roseobacter denitrificans Och 114(T) and Roseobacter litoralis Och 149(T) (95 % and 96 % sequence similarity, respectively) fall between strain SH4-1(T) and the Sulfitobacter cluster including Oceanibulbus indolifex HEL-45(T) (≥95.4 % sequence similarity). Cells of strain SH4-1(T) are irregular rods with at least one flagellum. Optimal growth occurred between 28 and 32 °C and at a pH between 7.0 and 8.5. Cells require the vitamin nicotinic acid amide as well as sodium ions for growth. The DNA G+C content was 55.1 mol%. The fatty acids (>1 %) comprised C10 : 0 3-OH, C12 : 1, C14 : 1 3-OH, C16 : 0, C18 : 0, C18 : 2, C18 : 1ω7c and 11-methyl C18 : 1ω7c. The polar lipid pattern indicated the presence of phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylmonomethylethanolamine, an unidentified aminolipid, one unidentified phospholipid and one other unidentified lipid. On the basis of phenotypic, chemotaxonomic and phylogenetic differences, strain SH4-1(T) represents a novel species in a new genus within the family Rhodobacteraceae, for which we propose the name Pelagimonas varians gen. nov., sp. nov. The type strain of the type species is SH4-1(T) ( = DSM 23678(T) = LMG 26343(T) = CIP 110297(T)).