Taxonomic characterization of denitrifying bacteria that degrade aromatic compounds and description of Azoarcus toluvorans sp nov and Azoarcus toluclasticus sp nov.

A taxonomic characterization of twenty-one strains capable of degrading aro matic compounds under denitrifying conditions, isolated from ten different geographical locations, was performed on the basis of general morphological and physiological characteristics, cellular fatty acids, DNA base composit ion, small ribosomal (16S) subunit DNA sequences, whole-cell protein patter ns and genomic DNA fragmentation analysis, in addition to DNA similarity es timations using hybridization methods. The collection of strains was subdiv ided into a number of different groups. A first group, consisting of four s trains, could be assigned to the previously described species Azoarcus tolu lyticus. A second group (five strains) had DNA which reannealed highly to t hat of strains of the first group, and it is considered to represent a geno movar of A. tolulyticus. The third and fourth groups, composed of a total o f five strains, represent a new species of Azoarcus, Azoarcus toluclasticus (group 3) and a genomovar of this species (group 4), respectively, Finally , the fifth group, with two strains, corresponds to another new species of the genus Azoarcus. Azoarcus toluvorans. In addition to these five groups, the collection includes five individual strains perhaps representing as man y different new species. The above classification is partially consistent w ith the results of approaches other than DNA-DNA hybridization (electrophor etic patterns of whole-cell proteins and of the fragments obtained after di gestion of total DNA with infrequently cutting restriction enzymes). On the other hand, no correlation of these groupings was found in terms of the ce llular fatty acid composition. It is also unfortunate that no simple sets o f easily determinable phenotypic properties could be defined as being chara cteristic of each of the groups.