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.
Highlights
Forty percent of hazardous wastes on the Environmental Protection Agency's (EPA) National Priority List (NPL) are co-contaminated with organic and heavy metals pollutants that pose healthy hazards to humans and wildlife[12,23]
The Minimal Inhibitory Concentration (MIC) of Cd2+, Zn2+, Cu2+ and Ni2+ in presence of phenol and cyanide analysis of P. putida strain PhCN cultures grown on as sole carbon and nitrogen sources, respectively, for phenol and cyanide indicated the presence of two large tested strains were lower than those observed in the plasmid elements[9]
Based on the fact that strains in the presence of aromatic compounds as the subsequent plasmid curing experiments demonstrated only source of carbon are only slightly lower than those that the ability to utilize phenol was encoded by the evaluated in the presence of glucose or malate
Summary
Forty percent of hazardous wastes on the Environmental Protection Agency's (EPA) National Priority List (NPL) are co-contaminated with organic and heavy metals pollutants that pose healthy hazards to humans and wildlife[12,23]. Isolation of bacterial strains that are able to degrade more than one organic pollutants such as phenol and cyanide, is becoming increasingly important for decontaminating polluted soil, sledges and ground water[7,13]. The use of these microorganisms may face various problems, including poor survival, substrate accessibility[16], or the presence of inhibitory compounds. Situations where simultaneous contamination by heavy metals and organic compounds are present can be expected and have been detected in industrial areas[1] For this reason, there is increasing interest[33] in bacterial strains that degrade aromatic compounds and tolerate toxic metals. To date, there have been no data on the interaction of genetic systems of aromatic compounds degradation, cyanide assimilation and metal resistance and their effect on physiology, biodegradation efficiency and the activity of the key enzyme in multifunctional strains
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