Precise Regulation of Differential Transcriptions of Various Catabolic Genes by OdcR via a Single Nucleotide Mutation in the Promoter Ensures the Safety of Metabolic Flux.

Synergistic regulation of the expression of various genes in a catabolic pathway is crucial for the degradation, survival, and adaptation of microorganisms in polluted environments. However, how a single regulator accurately regulates and controls differential transcriptions of various catabolic genes to ensure metabolic safety remains largely unknown. Here, a LysR-type transcriptional regulator (LTTR), OdcR, encoded by the regulator gene , was confirmed to be essential for 3,5-dibromo-4-hydroxybenozate (DBHB) catabolism and simultaneously activated the transcriptions of a gene with unknown function, , and three genes, , , and , involved in the DBHB catabolism in sp. strain H8. OdcB further metabolized the highly toxic intermediate 2,6-dibromohydroquinone, which was produced from DBHB by OdcA. The upregulated transcriptional level of was 7- to 9-fold higher than that of , , or in response to DBHB. Through an electrophoretic mobility shift assay and DNase I footprinting assay, DBHB was found to be the effector and essential for OdcR binding to all four promoters of , , and . A single nucleotide mutation in the regulatory binding site (RBS) of the promoter of (AT-N-ATG), compared to those of / (AT-N-ATG) and (AT-N-ATT), was identified and shown to enable the significantly higher transcription of . The precise regulation of these genes by OdcR via a single nucleotide mutation in the promoter avoided the accumulation of 2,6-dibromohydroquinone, ensuring the metabolic safety of DBHB. Prokaryotes use various mechanisms, including improvement of the activity of detoxification enzymes, to cope with toxic intermediates produced during catabolism. However, studies on how bacteria accurately regulate differential transcriptions of various catabolic genes via a single regulator to ensure metabolic safety are scarce. This study revealed a LysR-type transcriptional activator, OdcR, which strongly activated transcription for the detoxification of the toxic intermediate 2,6-dibromohydroquinone and slightly activated the transcriptions of other genes (, , and ) for 3,5-dibromo-4-hydroxybenozate (DBHB) catabolism in sp. strain H8. Interestingly, the differential transcription/expression of the four genes, which ensured the metabolic safety of DBHB in cells, was determined by a single nucleotide mutation in the regulatory binding sites of the four promoters. This study describes a new and ingenious regulatory mode of ensuring metabolic safety in bacteria, expanding our understanding of synergistic transcriptional regulation in prokaryotes.