CELLULAR FATTY-ACID COMPOSITION AS A CHEMOTAXONOMIC MARKER FOR THE DIFFERENTIATION OF PHENOSPECIES AND HYBRIDIZATION GROUPS IN THE GENUS AEROMONAS

Ninety genotypically characterized Aeromonas strains, including member s of all 14 currently established genospecies, were studied by perform ing gas-liquid chromatographic analysis of their cellular fatty acid m ethyl esters (FAMEs). A total of 44 fatty acids and two alcohols were found in members of the genus Aeromonas. All 90 strains contained 12:0 , 13:0 iso, 14:0, 15:0 iso 30H, 16:0, 16:1 omega 7c, 17:0 iso, iso 17: 1 omega 9c, summed feature 3 (16:1 iso I and/or 14:0 30H), and summed feature 7 (18:1 omega 7c, 18:1 omega 9t, and/or 18:1 omega 12t), where as all but one strain (99%) also contained 15:0 iso. Although the FAME profiles were very similar, minor quantitative variations could be us ed to differentiate phenospecies and/or hybridization groups. A cluste r analysis of the mean data revealed five FAME clusters, which were co mpared with phenotypic and genotypic groups identified in the genus Ae romonas. Hybridization groups that constituted the Aeromonas hydrophil a complex, the Aeromonas caviae complex, and the Aeromonas sobria comp lex were basically grouped into distinct FAME clusters. The taxonomic positions of hybridization groups 7 and 11 in these clusters, however, remained unclear. All of our results were highly reproducible. A new database of Aeromonas FAME fingerprints was generated, and this databa se can be used for rapid identification of unknown aeromonads. Using a large set of well-characterized aeromonads, we demonstrated for the f irst time that gas-liquid chromatographic FAME analysis can be used to differentiate the majority of the phenospecies and/or hybridization g roups in the genus Aeromonas.