Differentiation of Vibrionaceae Species by Their Cellular Fatty Acid Composition

The cellular fatty acid compositions of 10 Vibrio species, two Aeromoas species, three Photobacterium species, Plesiomonas shigelloides, and Escherichia coli Were determined by using capillary gas-liquid chromatography (GLC). The major fatty acids in all Vibrionaceae species and E. coli were hexadecenoic, hexadecanoic, and octadecenoic acids. Qualitative and quantitative differences in hydroxy, branched, and cyclopropane fatty acids and in isomers of unsaturated 16- and 18-carbon acids were used to divide the 29 strains belonging to 17 species tested into 13 GLC groups. Of the 13 groups, 10 contained one species, 2 contained two species, and 1 contained three species. All of the Vibrionaceae cultures were differentiated from E. coli (GLC group I) because the concentration of hexadecenoic acid was greater than the concentration of hexadecanoic acid; in E. coli, this ratio was reversed. Aeromonas hydrophila (GLC group II) and Aeromonas salmonicida (GLC group III) were differentiated from the Vibrio and Photobacterium species and from Plesiomonas shigelloides because the Aeromonas cultures did not contain 3-hydroxylauric acid. Seven of 10 Vibrio species, including Vibrio fluvialis (GLC group IV), Vibrio parahaemolyticus (GLC group V), Vibrio alginolyticus (GLC group V), Vibrio harveyi (GLC group V), Vibrio splendidus (GLC group VI), Vibrio vulnificus (GLC group VII), and Vibrio cholerae (GLC group VIII), contained both cis-9-hexadecenoic and cis-11-hexadecenoic acids. These seven species could be differentiated from Vibrio gazogenes (GLC group IX), Vibrio metschnikovii (GLC group XII), Vibrio anguillarum (GLC group XIII), Photobacterium leiognathi (GLC group XIII), Photobacterium phosphoreum (GLC group XI), Photobacterium angustum (GLC group XI), and Plesiomonas shigelloides (GLC group X) because these latter seven species did not contain cis-11-hexadecnoic acid. The only Vibrionaceae cultures which contained cyclopropane acids were Photobacterium phosphoreum, Photobacterium angustum, and one of the two strains of Plesiomonas shigelloides examined. Branched-chain acids were found in all species tested, and their concentrations ranged from less than 1 to 22%. Although the 16 Vibrionaceae species tested had many similarities in their cellular fatty acid compositions, there were differences which could be used for differentiation of members of this family at the genus and species levels.