Flavobacterium nitrogenifigens sp. nov., isolated from switchgrass (Panicum virgatum).

A yellow, nitrogen-fixing bacterial strain, NXU-44(T), isolated from the rhizosphere of switchgrass (Panicum virgatum) in Auburn, Alabama, USA, was studied to determine its taxonomic position. Cells of the isolate were rod-shaped and Gram-stain-negative. A comparison of the 16S rRNA gene sequence with the sequences of the type strains of the most closely related species showed that the strain belongs to the genus Flavobacterium with highest sequence similarities to the type strains of Flavobacterium ginsenosidimutans (97.9%), Flavobacterium phragmitis (97.6%) and Flavobacterium anhuiense (97.5%). The 16S rRNA gene sequence similarities to all other species of the genus Flavobacterium were below 97.5%. The fatty acid profile of strain NXU-44(T) consisted of the major fatty acids iso-C15 : 0, iso-C15 : 0 2-OH/C16 : 1ω7c and iso-C17 : 0 3-OH. The major compounds in the polar lipid profile were phosphatidylethanolamine, phosphatidylserine, one aminolipid and two polar lipids. The quinone system was composed exclusively of menaquinone MK-6. The polyamine pattern contained the major compound sym-homospermidine and only minor amounts of other polyamines. The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid. These data and the differential biochemical and chemotaxonomic properties show that strain NXU-44(T) represents a novel species of the genus Flavobacterium for which the name Flavobacterium nitrogenifigens sp. nov. is proposed. The type strain is NXU-44(T) ( = LMG 28694(T) = CIP 110894(T)).