Flavobacterium difficile sp. nov., isolated from a freshwater waterfall.

A bacterial strain designated KDG-16 T is isolated from a freshwater waterfall in Taiwan and characterized to determine its taxonomic affiliation. Cells of strain KDG-16 T are Gram-stain-negative, strictly aerobic, motile by gliding, rod-shaped and form light yellow colonies. Optimal growth occurs at 20-25 °C, pH 6-7, and with 0% NaCl. Phylogenetic analyses based on 16S rRNA gene sequences and an up-to-date bacterial core gene set reveal that strain KDG-16 T is affiliated with species in the genus Flavobacterium. Analysis of 16S rRNA gene sequences shows that strain KDG-16 T shares the highest similarity with Flavobacterium terrigena DSM 17934 T (97.7%). The average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization values between strain KDG-16 T and the closely related Flavobacterium species are below the cut-off values of 95-96, 90 and 70%, respectively, used for species demarcation. Strain KDG-16 T contains iso-C15:0, iso-C15:1 G and iso-C17:0 3-OH as the predominant fatty acids. The polar lipid profile consists of phosphatidylethanolamine, one uncharacterized aminophospholipid, one uncharacterized phospholipid, two uncharacterized aminolipids and two uncharacterized lipids. The major polyamine is homospermidine. The major isoprenoid quinone is MK-6. Genomic DNA G + C content of strain KDG-16 T is 31.6%. Based on the polyphasic taxonomic data obtained, strain KDG-16 T is considered to represent a novel species in the genus Flavobacterium, for which the name Flavobacterium difficile sp. nov. is proposed. The type strain is KDG-16 T (= BCRC 81194 T = LMG 31332 T).