Characterization of halobenzoate-degrading, denitrifying Azoarcus and Thauera isolates and description of Thauera chlorobenzoica sp. nov.

The taxonomic relationships of Azoarcus and Thauera isolates in the beta-subclass of the Proteobacteria capable of degrading fluoro-, chloro- or bromobenzoate under denitrifying conditions were analysed. A detailed classification of these strains was performed using a polyphasic approach, which included studies on morphology, phenotypic characterization, fatty acid analysis, 16S rRNA gene sequence analysis, 16S rRNA gene mapping (ribotyping) and DNA-DNA hybridization. The analyses of fatty acids and 16S rRNA gene sequencing differentiated strains 2FB2, 2FB6 and 4FB10 as new members of the genus Azoarcus and strains 4FB1, 4FB2, 3CB2, 3CB3 and 3BB1 as new members of the genus Thauera. DNA-DNA hybridization experiments established that strains 2FB2, 2FB6 and 4FB10 belong to the species Azoarcus tolulyticus. Strains 3CB2 and 3CB3 were assigned to the species Thauera aromatica on the basis of DNA-DNA hybridization and ribotyping experiments. Strains 4FB1, 4FB2 and 3BB1 showed close relatedness with strain 3CB-1T, previously described as T. aromatica genomovar chlorobenzoica. This group of strains is clearly differentiated from the species T. aromatica on the basis of 16S rRNA sequence analysis, DNA homology and ribotyping analysis. Strains 3CB-1T, 4FB1, 4FB2 and 3BB1 are proposed as members of the new species Thauera chlorobenzoica sp. nov., strain 3CB-1T (= ATCC 700723T) being the type strain.