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Dual two-component regulatory systems are involved in aromatic compound degradation in a polychlorinated-biphenyl degrader, Rhodococcus jostii RHA1.

ABSTRACT: A Gram-positive polychlorinated-biphenyl (PCB) degrader, Rhodococcus jostii RHA1, degrades PCBs by cometabolism with biphenyl. A two-component BphS1T1 system encoded by bphS1 and bphT1 (formerly bphS and bphT) is responsible for the transcription induction of the five gene clusters, bphAaAbAcAdC1B1, etbAa1Ab1CbphD1, etbAa2Ab2AcD2, etbAdbphB2, and etbD1, which constitute multiple enzyme systems for biphenyl/PCB degradation. The bphS2 and bphT2 genes, which encode BphS2 and BphT2, virtually identical to BphS1 (92%) and BphT1 (97%), respectively, were characterized. BphS2T2 induced the activation of the bphAa promoter in a host, Rhodococcus erythropolis IAM1399, in the presence of a variety of aromatics, including benzene, toluene, ethylbenzene, xylenes, isopropylbenzene, and chlorinated benzenes, as effectively as BphS1T1. The substrate spectrum of BphS2T2 was the same as that of BphS1T1, except for biphenyl, which is a substrate only for BphS1T1. BphS2T2 activated transcription from the five promoters of biphenyl/PCB degradation enzyme gene clusters as effectively as BphS1T1. The targeted disruptions of the bphS1, bphS2, bphT1, and bphT2 genes indicated that all these genes are involved in the growth of RHA1 on aromatic compounds. The hybrid system with bphS1 and bphT2 and that with bphS2 and bphT1 were constructed, and both systems conducted induced activation of the bphAa promoter, indicating cross-communication. These results indicated that RHA1 employs not only multiple enzyme systems, but also dual regulatory systems for biphenyl/PCB degradation. Comparison of the sequences, including bphS2T2, with the bphS1T1-containing sequences and the corresponding sequences in other rhodococcal degraders suggests that bphS2T2 might have originated from bphS1T1.

SUBMITTER: Takeda H

PROVIDER: S-EPMC2937422 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Dual two-component regulatory systems are involved in aromatic compound degradation in a polychlorinated-biphenyl degrader, Rhodococcus jostii RHA1.

Takeda Hisashi H Shimodaira Jun J Yukawa Kiyoshi K Hara Naho N Kasai Daisuke D Miyauchi Keisuke K Masai Eiji E Fukuda Masao M

Journal of bacteriology 20100709 18

A Gram-positive polychlorinated-biphenyl (PCB) degrader, Rhodococcus jostii RHA1, degrades PCBs by cometabolism with biphenyl. A two-component BphS1T1 system encoded by bphS1 and bphT1 (formerly bphS and bphT) is responsible for the transcription induction of the five gene clusters, bphAaAbAcAdC1B1, etbAa1Ab1CbphD1, etbAa2Ab2AcD2, etbAdbphB2, and etbD1, which constitute multiple enzyme systems for biphenyl/PCB degradation. The bphS2 and bphT2 genes, which encode BphS2 and BphT2, virtually identi ...[more]

PMID: 20622058

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Project description:The two 2-hydroxy-6-oxohepta-2,4-dienoate (HOHD) hydrolase genes, etbD1 and etbD2, were cloned from a strong polychlorinated biphenyl (PCB) degrader, Rhodococcus sp. strain RHA1, and their nucleotide sequences were determined. The etbD2 gene was located in the vicinity of bphA gene homologs and encoded an enzyme whose amino-terminal sequence was very similar to the amino-terminal sequence of the HOHD hydrolase which was purified from RHA1. Using the etbD2 gene fragment as a probe, we cloned the etbD1 gene encoding the purified HOHD hydrolase by colony hybridization. Both genes encode a product having 274 amino acid residues and containing the nucleophile motif conserved in alpha/beta hydrolase fold enzymes. The deduced amino acid sequences were quite similar to the amino acid sequences of the products of the single-ring aromatic hydrolase genes, such as dmpD, cumD, todF, and xylF, and not very similar to the amino acid sequences of the products of bphD genes from PCB degraders, including RHA1. The two HOHD hydrolase genes and the RHA1 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate (HPDA) hydrolase gene, bphD, were expressed in Escherichia coli, and their relative enzymatic activities were examined. The product of bphD was very specific to HPDA, and the products of etbD1 and etbD2 were specific to HOHD. All of the gene products exhibited poor activities against the meta-cleavage product of catechol. These results agreed with the results obtained for BphD and EtbD1 hydrolases purified from RHA1. The three hydrolase genes exhibited similar induction patterns both in an RNA slot blot hybridization analysis and in a reporter gene assay when a promoter probe vector was used. They were induced by biphenyl, ethylbenzene, benzene, toluene, and ortho-xylene. Strain RCD1, an RHA1 mutant strain lacking both the bphD gene and the etbD2 gene, grew well on ethylbenzene. This result suggested that the etbD1 gene product is involved in the meta-cleavage metabolic pathway of ethylbenzene.

Dataset Information

Dual two-component regulatory systems are involved in aromatic compound degradation in a polychlorinated-biphenyl degrader, Rhodococcus jostii RHA1.

Publications

Dual two-component regulatory systems are involved in aromatic compound degradation in a polychlorinated-biphenyl degrader, Rhodococcus jostii RHA1.

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