A Gram-negative bacterium, designated strain EMB34(T), was isolated from a wastewater treatment plant in Korea. Growth was observed between 10 and 40 degrees C (optimum, 25-35 degrees C) and between pH 6.0 and 9.5 (optimum, pH 7.5-8.0). The cells were non-motile rods, linked with extracellular fibrils. The predominant fatty acids of strain EMB34(T) were iso-C(15 : 0), C(15 : 0), iso-C(15 : 1) G, iso-C(16 : 0) 3-OH and iso-C(15 : 0) 3-OH and the strain contained phosphatidylethanolamine and phosphatidylinositol as the polar lipids. The G+C content of the genomic DNA was 34.2 mol% and the major quinone was menaquinone-6. Comparative 16S rRNA gene sequence analyses showed that strain EMB34(T) formed a distinct phyletic line within the genus Flavobacterium. The levels of 16S rRNA gene sequence similarity with other Flavobacterium species were less than 94.5 %. On the basis of phenotypic, chemotaxonomic and molecular data, it is clear that strain EMB34(T) represents a novel species within the genus Flavobacterium, for which the name Flavobacterium filum sp. nov. is proposed. The type strain is EMB34(T) (=KCTC 12610(T)=DSM 17961(T)).