Isolation of Desulfomicrobium orale sp nov and Desulfovibrio strain NY682,oral sulfate-reducing bacteria involved in human periodontal disease

The species of sulfate-reducing bacteria that prevail in sites affected by periodontal disease may be different from those commonly occurring in the d igestive tracts of healthy individuals. Ten strains of mesophilic sulfate-r educing bacteria (SRB) were isolated from subgingival plaque in periodontal lesions of ten patients with periodontitis. Characterization on the basis of morphological, physiological and phylogenetic properties demonstrated tw o distinct types of oral SRB, One strain was a curved rod with high motilit y. For dissimilatory sulfate reduction, lactate or pyruvate was oxidized in completely to equimolar amounts of acetate. Desulfoviridin and cytochrome c (3) were present in this mesophilic vibrio and the cellular lipid profile w as similar to that from members of the genus Desulfovibrio. The 16S rDNA se quence was similar to that of the proposed 'Desulfovibrio fairfieldensis'. Cells of the nine other strains were straight, rod-shaped, exhibited a low growth rate and oxidized substrates incompletely to acetate. These SRB, lik e members of the genus Desulfomicrobium, lacked desulfoviridin. Analysis of the 16S rDNA sequences of seven of the nine isolates showed a high degree of similarity among these oral strains, forming a distinct lineage within t he genus Desulfomicrobium, The cellular lipid profile of a representative o ral strain, NY678(T), was in accordance with that of other Desulfomicrobium species, but also showed dissimilar features. The phenotypic and phylogene tic analyses indicate that these rod-shaped SRB from the oral cavity could be regarded as a new species, for which the designation Desulfomicrobium or ale sp. nov. is proposed.