Genes Involved in the Benzoate Catabolic Pathway in Acinetobacter calcoaceticus PHEA-2
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A putative benM gene encoding a LysR-type regulator located upstream from the benA gene was found in Acinetobacter calcoaceticus PHEA-2. Disruption of benM or benA destroyed the ability of PHEA-2 to utilize benzoate. The benM mutant was used to construct a genomic library for isolation of the complete gene cluster responsible for benzoate degradation. Sequence analysis showed that the cluster has three putative operons: benM, benABCDE, and benKP. Unlike many well-characterized benzoate-degrading bacteria, muconate is unable to induce in vivo transcription of the PHEA-2 ben cluster. Reverse transcriptase-polymerase chain reaction (RT-PCR) results showed that the benABCDE operon is activated by the BenM protein in the presence of benzoate. Moreover, a gel-retardation assay demonstrated that BenM binds to the promotor region of the benA gene. The activities of catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O) showed that PHEA-2 converted benzoate to catechol for further degradation, possibly via an ortho-cleavage pathway.
KeywordsCatechol Ethylene Diamine Tetraacetic Acid Ethylene Diamine Tetraacetic Acid benA Muconate
We thank Dr. Masahiro Takeo (Hyogo University, Japan) for helpful comments. This work was supported by the Ministry of Science and Technology of China (National Basic Research Program 2007CB707805 and 2007CB109203, and National High-Tech Program 2007AA021304 and 2006AA020101) and the National Natural Science Foundation of China (30470047 and 30770076).
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