Pathways of 3-Chlorobenzoate Degradation by Rhodococcus opacus strains 1CP and 6a


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Abstract

3-Chlorobenzoic acid (3-CBA) is widely used as a precursor/preservative in industry and agriculture and is therefore a known environmental contaminant. The key stages of 3-CBA decomposition by Rhodococcus opacus strains 1CP and 6a were studied. Comparative characterization of the substrate specificity of 3-chlorobenzoate 1,2-dioxygenase (3-CBA 1,2-DO), induced in the strains grown in the presence of 3‑CBA, was carried out. These enzymes were established to have a wider substrate specificity than the benzoate 1,2-dioxygenase (1,2-BDO) of R. opacus strain 1CP, which is induced during growth of R. opacus strain 1CP in the presence of benzoate. Benzoate, 3-CBA, and 3,4-dihydroxybenzoate served as substrates for 3‑CBA 1,2-DO. During the degradation of 3-CBA by R. opacus 1CP cells, both 3-chloro- and 4-chlorocatechol (3-CCat and 4-CCat) were detected. R. opacus 6a efficiently degraded 3-CBA without accumulation of intermediates. The difference in the pathways of 3-CBA degradation by these strains was shown: via the pathway of ortho-cleavage of 3-chlorocatechol in R. opacus 1CP and of 4-chlorocatechol in R. opacus 6a. In the genome of the strain R. opacus 6a, the genes encoding chlorocatechol 1,2-dioxygenase and chloromuconate cycloisomerase were found, which were 98-99% identical to the genes of R. opacus 1CP encoding 4‑chlorocatechol 1,2-dioxygenase (4-CCat 1,2-DO) and 3-chloromuconate cycloisomerase (3-CMCI) of the modified ortho-cleavage pathway for conversion of 4-chlorocatechol (the intermediate of 4-chlorophenol degradation). It was shown for the strains under study that implementation of different pathways for 3-CBA decomposition was predestined not by the metabolic capabilities of bacteria, but by the substrate specificity of 3-CBA 1,2-DO, the enzyme that initiates 3-CBA degradation.

About the authors

I. P. Solyanikova

Skryabin Institute of Biochemistry and Physiology of Microorganisms, FRC “Pushchino Scientific Centre
of Biological Research”, Russian Academy of Sciences

Author for correspondence.
Email: innas@IBPM.Pushchino.ru
Russian Federation, Pushchino, 142290

E. V. Emelyanova

Skryabin Institute of Biochemistry and Physiology of Microorganisms, FRC “Pushchino Scientific Centre
of Biological Research”, Russian Academy of Sciences

Email: innas@IBPM.Pushchino.ru
Russian Federation, Pushchino, 142290

E. S. Shumkova

Bach Institute of Biochemistry, Research Center for Biotechnology, Russian Academy of Sciences

Email: innas@IBPM.Pushchino.ru
Russian Federation, Moscow, 119071

V. M. Travkin

Gorin Belgorod State Agrarian University

Email: innas@IBPM.Pushchino.ru
Russian Federation, May, 308503

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