CELLULAR FATTY-ACID COMPOSITION OF DESULFOVIBRIO SPECIES AND ITS USE IN CLASSIFICATION OF SULFATE-REDUCING BACTERIA

Forty strains of non-sporeforming sulfate-reducing bacteria including eighteen type strains of the genus Desulfovibrio and six type strains of other genera have been analysed for their cellular fatty acid (FA) composition. Iso-branched 17:1 FA, regarded as a biomarker FA for the genus Desulfovibrio, and, in many cases, also iso-15:0 FA predominated in most Desulfovibrio species, in Desulfomicrobium and Desulfomonas, but their proportions were significantly lower (1.6-9.5%) in D. alcoholovorans, D. carbinolicus, D. fructosovorans, D. giganteus, D. gigas DSM 496 and D. sulfodismutans. The latter species had anteiso-15:0 FA (30-54%) as the major FA. Iso-17:1 FA was absent in D. baarsii, D. gigas DSM 1382 T, D. sapovorans and D. thermophilus. The overall FA composition of D. baarsii, D. thermophilus, Desulfobacter curvatus, Desulfobacterium autotrophicum, Desulfuromonas acetoxidans and Thermodesulfobacterium commune was very distinct from those of what may be called 'true'' desulfovibrios. Surprisingly, Desulfobacterium autotrophicum did not contain iso or anteiso FA, but contained 10-methyl 16:0 FA which is reported for the first time in a member of this genus. The structure of the dendrogram produced by numerical cluster analysis of the FA composition of all strains studied was in good agreement with the phylogenetic relationships of the organisms. Most desulfovibrios clustered in two separate groups reflecting the different distribution of iso-17:1 FA. Some desulfovibrios, e.g. D. gigas DSM 496, and salt requiring strains D. desulfuricans El Agheila Z and D. vulgaris DSM 1744, did not cluster with the respective type strain indicating that they might have been incorrectly classified. On the other hand, transfer of D. baculatus to Desulfomicrobium and of D. thermophilus to Thermodesulfobacterium, as recently suggested, is clearly supported by our FA data.