A Gram-staining-negative, non-motile, catalase- and oxidase-positive strain, designated MS7(T), was isolated from freshwater of a river near Trabzon, Turkey. Its taxonomy was investigated using a polyphasic approach. The strain grew optimally at 28 degrees C and pH 7.5 and in the presence of 2.0% NaCl. 16S rRNA gene sequence analysis revealed that the strain belonged to the genus Algoriphagus; strain MS7(T) showed highest sequence similarity to the type strains of Algoriphagus alkaliphilus (97.3%), Algoriphagus terrigena (96.8%), Algoriphagus jejuensis (96.2 %), Algoriphagus boritolerans (96.1 %) and Algoriphagus aquatilis (95.8 %). The major fatty acids of strain MS7(T) were iso-C-15:0 (30.14%) and summed future 9 (10-methyl C-16:0 and/or iso-C(17:1)w9c 18.75%). Polar lipid analysis revealed phosphatidylethanolamine, a variety of unidentified lipids, an unidentified aminophospholipid, an unidentified phospholipid and an unidentified aminolipid. The major isoprenoid quinone was MK-7.The DNA G+C content of MS7(T) was 41.6 mol%, a value consistent with that of members of the genus Algoriphagus. The level of DNA-DNA relatedness between strain MS7(T) and A. alkaliphilus LMG 22694(T) was 41 %, which is clearly below the 70% threshold accepted for species delineation. Thus, our results support the placement of strain MS7(T) within a separate and previously unrecognized species. On the basis of these data, the strain is considered to represent a novel species of the genus Algoriphagus, for which the name Algoriphagus trabzonensis sp. nov. is proposed. The type strain is MS7(T) (=NCCB 100372(T)=LMG 26290(T)). An emended description of A. alkaliphilus is also provided.