A Gram-negative, non-spore-forming, non-motile bacterium, strain A8-7(T), was isolated from fresh water of a slightly alkaline lake, Longhu Lake, in Daqing, north-east China, and its taxonomic position was studied by using a polyphasic approach. Strain A8-7(T) was aerobic, heterotrophic and positive for catalase and oxidase. It grew at 20-37 degrees C (optimum 30 degrees C) and pH 5.5-10.5 (optimum pH 7.5) and in the presence of 0-3 % (w/v) NaCl. It formed pink-pigmented, smooth and circular colonies, 1-2 mm in diameter, on R3A-V agar plates after incubation at 30 degrees C for 3 days. Cells of strain A8-7(T) were rods, 0.2-0.4 mum wide and 1.6-4.0 mum long. The major fatty acids (>10 %) were iso-C(15 : 0) (40.3 %) and summed feature 3 (C(16 : 1)omega7c and/or iso-C(15 : 0) 2-OH; 12.1 %). The menaquinone was MK-7. The DNA G+C content was 43 mol% (T(m)). Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain A8-7(T) was phylogenetically related to members of the genus Algoriphagus, with sequence similarities of 92.6-95.2 %, the highest sequence similarity being to the sequence from Algoriphagus mannitolivorans IMSNU 14012(T). On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain A8-7(T) was considered to represent a novel species of the genus Algoriphagus, for which the name Algoriphagus aquatilis sp. nov. is proposed. The type strain is A8-7(T) (=CGMCC 1.7030(T) =NBRC 104237(T)).