| Title |
Molecular Characterization of Chloranilic Acid Degradation in Pseudomonas putida TQ07 |
| Author |
Luis G. Treviño-Quintanilla1*, Julio A. Freyre-González2, Rosa A. Guillén-Garcés1, and Clarita Olvera3 |
| Address |
1Departamento de Tecnología Ambiental, Universidad Politécnica del Estado de Morelos. Blvd. Cuauhnáhuac 566, Col. Lomas del Texcal, 62550. Jiutepec, Morelos, México, 2Programa de Dinámica Genómica, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México. Av. Universidad s/n, Col. Chamilpa, 62210. Cuernavaca, Morelos, México, 3Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apartado postal 510-3. C. P. 62250, Cuernavaca, Morelos, México |
| Bibliography |
Journal of Microbiology, 49(6),974-980, 2011,
|
| DOI |
|
| Key Words |
pentachlorophenol, chloranilic acid, biodegradation, Pseudomonas putida, pyrone dicarboxylic acid hydrolase, LysR regulator |
| Abstract |
Pentachlorophenol is the most toxic and recalcitrant chlorophenol because both aspects are directly proportional to the halogenation degree. Biological and abiotic pentachlorophenol degradation generates p-chloranil, which in neutral to lightly alkaline environmental conditions is hydrolyzed to chloranilic acid that present a violet-reddish coloration in aqueous solution. Several genes of the degradation pathway, cadR-cadCDX, as well as other uncharacterized genes (ORF5 and 6), were isolated from a chloranilic acid degrading bacterium, Pseudomonas putida strain TQ07. The disruption by random mutagenesis of the cadR and cadC genes in TQ07 resulted in a growth deficiency in the presence of chloranilic acid, indicating that these genes are essential for TQ07 growth with chloranilic acid as the sole carbon source. Complementation assays demonstrated that a transposon insertion in mutant CAD82 (cadC) had a polar effect on other genes contained in cosmid pLG3562. These results suggest that at least one of these genes, cadD and cadX, also takes part in chloranilic acid degradation. Based on molecular modeling and function prediction, we strongly suggest that CadC is a pyrone dicarboxylic acid hydrolase and CadD is an aldolase enzyme like dihydrodipicolinate synthase. The results of this study allowed us to propose a novel pathway that offers hypotheses on chloranilic acid degradation (an abiotic by-product of pentachlorophenol) by means of a very clear phenotype that is narrowly related to the capability of Pseudomonas putida strain TQ07 to degrade this benzoquinone. |
