Bioremediation of Methomyl by Soil Isolate – Pseudomonas Aeruginosa

Abstract

Bioremediation is emerging as one of the most promising technology for the removal of xenobiotics. Bioremediation of xenobiotic compounds by microorganisms is a crucial phenomenon by which these compounds can be detoxified or removed from the environment, thus preventing pollution, where screening of the potential degrading organism is one of the key step. Methomyl belonging to N-methyl carbamate group of insecticide is the most commonly used pesticide on fruits and vegetables. It is classified as a toxic, hazardous and restricted use pesticide by the World Health Organization (WHO), European Commission (EC) and Environmental Protection Act (EPA). The present study is therefore aimed to isolate a soil bacterium, characterize the most potential degrader of methomyl and further determine the role of plasmid in bioremediation. Soil samples were collected from different areas around Karnatak University campus, Dharwad and inoculated in minimal medium containing methomyl (10-3 M). Morphological characteristics of ten isolates were studied and subjected to HPLC analysis where methomyl degradation (%) was observed. The most potential strain with the ability to degrade methomyl was inoculated in synthetic medium containing methomyl (10-3 M) for 96 hrs. This strain was further identified morphologically, biochemically and genetically. The results indicated that the isolated strain was gram -ve rods and biochemical characteristics showed that indole, methyl red, vogues prauskauer and H2S test was negative and citrate, catalase, gelatin hydrolysis and oxidase test was positive. The 16Sr DNA reports revealed that the accession number was G01801181 and showed 99% similarity to Pseudomonas aeruginosa. The present study on HPLC analysis at regular intervals of 24 hrs of the soil isolate - Pseudomonas aeruginosa in synthetic medium containing methomyl (10-3 M) incubated for 96 hrs revealed that there was a significant decrease in the methomyl content in the treated group when compared with the initial control demonstrating its potential use in bioremediation. The plasmid isolation and curing study confirmed that the genes of the plasmid of Pseudomonas aeruginosa are involved in the methomyl degradation and such plasmids could be used as recombinant DNA technology for bioremediation.