A Gram-negative bacterium, designated strain EMB117T, was isolated from a municipal wastewater treatment plant and characterized by polyphasic taxonomy. The cells were non-spore-forming rods that showed gliding motility. Optimal growth occurred at 25-30 degrees C and pH 7.0-8.0. Strain EMB117T contained phosphatidylethanolamine as the predominant polar lipid, and the major fatty acids were iso-C(15 : 0), iso-C(17 : 0) 3-OH, iso-C(15 : 0) 3-OH and summed feature 3 (C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH). The G+C content of the genomic DNA was 33.5 mol% and the major isoprenoid quinone was MK-6. A phylogenetic analysis based on 16S rRNA gene sequences showed that strain EMB117T belonged to the genus Flavobacterium and was most closely related to Flavobacterium johnsoniae DSM 425(T) (97.8 % sequence similarity). The DNA-DNA relatedness between strain EMB117T and F. johnsoniae ATCC 17061T was about 18 %. On the basis of the phenotypic, chemotaxonomic and molecular data, strain EMB117T represents a novel species within the genus Flavobacterium, for which the name Flavobacterium defluvii sp. nov. is proposed. The type strain is EMB117T (=KCTC 12612T=DSM 17963T).