Degradative Plasmid and Heavy Metal Resistance Plasmid Naturally Coexist in Phenol and Cyanide Assimilating Bacteria

Abstract

Problem statement: Heavy metals are known to be powerful inhibitors of xenobiotics biodegradation activities. Alleviation the inhibitory effect of these metals on the phenol biodegradation activities in presence of heavy metals resistant plasmid was investigated. Approach: Combination of genetic systems of degradation of xenobiotic compound and heavy metal resistance was one of the approaches to the creation of polyfunctional strains for bioremediation of soil after co-contamination with organic pollutants and heavy metals. Results: A bacterial strain Pseudomonas putida PhCN (pPhCN1, pPhCN2) had been obtained. This bacterium contained two plasmids, a 120 Kb catabolic plasmid that encode for breakdown of phenol (pPhCN1) and pPhCN2 plasmid (100 Kb) that code for cadmium and copper resistant. Cyanide assimilation by this bacterium was encoded by chromosomal genes. The inhibitory effect of cadmium (Cd²⁺) or copper (Cu²⁺) on the degradation of phenol and cyanide by P. putida strains PhCN and PhCN1 (contained pPhCN1) were investigated. The resistant strain PhCN showed high ability to degrade phenol and cyanide in presence of Cd²⁺ or Cu²⁺ comparing with the sensitive strain PhCN1. In addition, Cd²⁺ or Cu²⁺ was also found to exert a strong inhibitory effect on the C23O dioxygenase enzyme activity in the presence of cyanide as a nitrogen source. Conclusion: The presence of heavy metal resistance plasmid alleviated the inhibitory effect of metals on the phenol and cyanide assimilation by resistant strain.