Abstract：Phenol is a key chemical engineering material, which is detrimental to the agroecological environment. In Thauera aromatica strain K172, a denitrifying bacterium, phenol undergoes phosphorylation and carboxylation and is converted into 4-hydroxybenzoic acid, which is less toxic. Phenylphosphate carboxylase, consists of α, δ, β and γ subunits, is a key enzyme of phenol degradation process. This study used the open reading frames, orf 5 and orf 12, which encode the δ and γ subunits, as the templates of DNA probes to analyze the diversity of related genes in strains of T. aromatica and Azoarcus evansii by Southern blot. The results indicated that these strains all contained several orf 5 homologs. The hybridization map showed there was no genus specificity of the gene. By contrast, orf 12 was only present in T. aromatica K172, S100 and A. evansii T and the gene cluster related to phenol degradation had a single copy in the genome. The gene was mapped to a PstⅠ digest fragment whose size was consistent among the bacterial strains. While in the bacterial culture experiments, only these 3 strains grew steadily on phenol as the only carbon source under the condition of denitrification. Therefore, our results suggested that T. aromatica K172, S100 and A. evansii T possessed the ability of phenol degradation through the same pathway. It is possible that the bacteria acquired the identical genes or gene cluster during evolution. This study provids new evidence of previous research that γ protein encoded by orf 12 is one subunit of phenylphosphate carboxylase. Meanwhile this work offers available scientific evidences for further studies of phenol degradation.
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