PHYLOGENETIC ANALYSES OF A NEW GROUP OF DENITRIFIERS CAPABLE OF ANAEROBIC GROWTH ON TOLUENE AND DESCRIPTION OF AZOARCUS-TOLULYTICUS SP-NOV

To understand the phylogeny and taxonomy of eight new toluene-degradin g denitrifying isolates, we performed a 16S rRNA sequence analysis and a gas chromatographic analysis of their cellular fatty acids and exam ined some of their biochemical and physiological features, These isola tes had 16S rRNA sequence signatures identical to those of members of the beta subclass of the Proteobacteria. The levels of similarity were as follows: 97.9 to 99.9% among the new isolates; 91.2 to 92.4% betwe en the new isolates and Azoarcus sp, strain S5b2; 95.3 to 96.2% betwee n the new isolates and Azoarcus sp, strain BH72; and 94.8 to 95.3% bet ween the new isolates and Azoarcus indigens VB32(T) (T = type strain), Phylogenetic trees constructed by using the distance matrix, maximum- parsimony, and maximum-likelihood methods showed that our eight denitr ifying isolates form a phylogenetically coherent cluster which represe nts a sister lineage of the previously described Azoarcus species, Fur thermore, the fatty acid profiles, the cell morphology, and several ph ysiological and nutritional characteristics of the eight isolates and the previously described members of the genus Azoarcus were also simil ar, In contrast to the previously described members of the genus Azoar cus, the eight new isolates were capable of degrading toluene under de nitrifying conditions, We concluded that these toluene-degrading denit riflers are members of a new species of the novel nitrogen-fixing genu s Azoarcus, We propose the name Azoarcus tolulyticus for these toluene -degrading denitrifying isolates and designate strain Tol-4 the type s train.