Carbon Catabolite Repression of Methyl Parathion Degradation in a Bacterial Isolate Characterized as a Cupriavidus sp. LMGR1

Abstract

Among the mixture of carbon compounds, bacteria have the ability to select energetically efficient substrate as a preferred carbon source. This specific behavior often limits the use of pollutants as a secondary carbon source by bacteria grown with preferred carbon source and the pollutants. Therefore, to develop an efficient bioremediation technology for removal/degradation of organophosphorus pesticide methyl parathion (MP) from agricultural soils, a soil bacterial strain (LMGR1) capable of degrading MP and p-nitrophenol was isolated and identified as a Cupriavidus oxalaticus based on biochemical (carbon utilization pattern) and molecular analysis (16S rRNA gene sequence), but the phylogenetic analysis revealed a distinct position, and the name was designated as Cupriavidus sp. LMGR1. The effect of preferred carbon source on degradation was also investigated. The bacterium assimilated the pesticide as a sole source of carbon and consumes about 100 mg L−1 of MP within 6 to 7 h of incubation. Furthermore, the methyl parathion hydrolase (MPH) enzyme (localized in the periplasm of bacterium) activity was induced by the carbon deficiency instead of substrate. Determination of kinetic parameters, i.e., Vmax and Km for MPH enzyme in the extracted periplasmic protein indicated significant higher affinity towards the substrate. The reduced MPH activity in the bacterium grown in presence of preferred carbon source indicated the role of carbon catabolite repression in regulation of pesticide degradation. Thus, the bacterium has prodigious capability to be used as a bioremediation agent, but the availability of preferred carbon source may affect its potential in field application.