The taxonomic position of three bacterial strains, Asr22-19T, NBRC 101035 and NBRC 101041, isolated from shellfish in Japan, was determined by using a polyphasic taxonomic approach. The strains were facultatively anaerobic, motile by gliding and Gram-staining-negative slender rods. Their major respiratory quinone was menaquinone-7 and their predominant cellular fatty acids were iso-C15:0, iso-C17:0 3-OH, iso-C15:0 3-OH, C16:0 3-OH, and C16:0. The G+C content of the genomic DNA was 42.0-42.7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strains clustered with the genus Persicobacter in the family 'Flammeovirgaceae'. DNA-DNA relatedness values were higher than 68% among strains Asr22-19T, NBRC 101035 and NBRC 101041, and were lower than 28% between strain Asr22-19T and Persicobacter diffluens NBRC 15940T. The three novel strains could be differentiated from Persicobacter diffluens by several phenotypic characteristics. On the basis of these results, the novel species Persicobacter psychrovividus sp. nov. (type strain Asr22-19T=NBRC 101262T=CIP 109100T) is proposed and emended descriptions are given for the genus Persicobacter and for Persicobacter diffluens.