A yellowish, flexirubin-pigment-producing strain I3-3T was isolated from river water in Iksan, the Republic of Korea. The strain was gram-negative, aerobic, non-motile, showed catalase and oxidase activities, and could grow at a temperature range of 10-35°C, pH 5.0-10 and 0-2.0% (w/v) of NaCl. The major fatty acids were iso-C15:0, iso-C17:0 3-OH and summed feature 3 (comprising C16:1ω7c and/or C16:1ω6c). The isolate contained phosphatidylethanolamine, one aminolipid, and two unidentified lipids as the major polar lipids. Menaquinone-6 (MK6) was the major respiratory quinone. The G+C content of the genomic DNA of strain I3-3T was 35.6%. Comparison of the 16S rRNA gene sequence with the sequences of the closely related type strains showed highest sequence similarity of 96.95% and 96.93% to Flavobacterium nitrogenifigens NXU-44T and Flavobacterium compostarboris 15C3T, respectively. Based on phenotypic and phylogenetic distinctiveness, strain I3-3T is considered as a member of novel species within the genus Flavobacterium, for which Flavobacterium amnigenum sp. nov. is proposed. The type strain is I3-3T (=KCTC 52884T =NBRC 112871T).
Keywords: Flavobacterium amnigenum; freshwater; polyphasic characterization.