Ralstonia pickettii DTP0602 utilizes 2,4,6-trichlorophenol (2,4,6-TCP) as sole source of carbon and energy. We have characterized
hadABC which is involved in the degradation of 2,4,6-TCP. To identify the other genes involved in 2,4,6-TCP degradation, the DNA sequence around
hadABC was determined. A regulatory gene,
hadR, homologous to the LysR-type transcriptional regulator was located upstream of
hadA, but no maleylacetate (MA) reductase gene was located near
hadABC. An 8.4-kb DNA fragment containing a MA reductase gene,
hadD, was cloned using a DNA probe designed from the N-terminal sequence of purified MA reductase.
hadD was located upstream of an open reading frame,
hadS, which codes for a homolog of the LysR-type transcriptional regulator. A
hadS insertion mutant, DTP62S, constitutively expressed MA reductase when grown on aspartate in the absence of 2,4,6-TCP. MA reductase was repressed in DTP62S supplemented with
hadS. HadR and HadS are proposed to be a positive and a negative regulator, respectively. A draft genome sequence analysis revealed that the
hadRXABC and
hadSYD clusters were separated by 146-kb on the 8.1-Mb chromosome.
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