Abstract
Phenol- and naphthalene-degrading indigenous Pseudomonas pseudoalcaligenes strain C70 has great potential for the bioremediation of polluted areas. It harbours two chromosomally located catechol meta pathways, one of which is structurally and phylogenetically very similar to the Pseudomonas sp. CF600 dmp operon and the other to the P. stutzeri AN10 nah lower operon. The key enzymes of the catechol meta pathway, catechol 2,3-dioxygenase (C23O) from strain C70, PheB and NahH, have an amino acid identity of 85%. The metabolic and regulatory phenotypes of the wild-type and the mutant strain C70ΔpheB lacking pheB were evaluated. qRT-PCR data showed that in C70, the expression of pheB- and nahH-encoded C23O was induced by phenol and salicylate, respectively. We demonstrate that strain C70 is more effective in the degradation of phenol and salicylate, especially at higher substrate concentrations, when these compounds are present as a mixture; i.e., when both pathways are expressed. Moreover, NahH is able to substitute for the deleted PheB in phenol degradation when salicylate is also present in the growth medium. The appearance of a yellow intermediate 2-hydroxymuconic semialdehyde was followed by the accumulation of catechol in salicylate-containing growth medium, and lower expression levels and specific activities of the C23O of the sal operon were detected. However, the excretion of the toxic intermediate catechol to the growth medium was avoided when the growth medium was supplemented with phenol, seemingly due to the contribution of the second meta pathway encoded by the phe genes.
Highlights
In nature, aromatics are an extensively distributed class of organic compounds
The aim of the present research was to identify the physiological role of C23Os in P. pseudoalcaligenes strain C70 and to evaluate their potential to degrade a mixture of phenol and salicylate
One of them is a part of the phenol degradation operon pheRKLMNOPQBCDEFGHI, which is structurally similar to the dmp operon of Pseudomonas sp
Summary
Aromatics are an extensively distributed class of organic compounds. Xenobiotic aromatic pollutants are usually the major concern because of their environmental persistence and toxicity to living organisms. Microorganisms possess biochemical pathways enabling them to use these compounds as sole carbon and energy sources [1,2,3,4]. Redundant catechol degradation meta pathways of P. pseudoalcaligenes C70
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