G. Manigandan and R. Nelson
Soil samples contaminated with pesticides were collected from agricultural fields in and around Pudukkottai district, TamilNadu. Samples were inoculated into mineral salts medium with Lambda cyhalothrin as the sole source of carbon and incubated for 12 days. Intermittent addition of pesticide was carried out for enrichment of cultures. Bacteria capable of degrading lambda cyhalothrin were isolated on mineral salts agar medium. From the 6 samples collected, 52 isolates capable of degrading lambda cyhalothrin was obtained, majority of them being gram negative in nature. Out of these, 3 were capable of showing good growth in mineral salts medium. Screening of the isolates for their efficiencies in degrading lambda cyhalothrin was carried out based on enrichment technique, spectrometric analysis and HPLC studies. Strains JJC1, JJC2 and JJC3 showed the highest tolerance to the pesticide. JJC1 and JJC2 were identified as Stenotrophomonas maltophilia and Enterococcus faecalis respectively based on 16S rRNA and phylogenetic tree analysis. JJC3 was identified as Pseudomonas fluorescens based on cell morphology and various biochemical tests. Of the 3 isolates, Stenotrophomonas maltophilia was found to be effective in tolerating and degrading lambda cyhalothrin. Hence it was used in further studies. The biomass and cell growth were determined initially for three consecutive days for Stenotrophomonas maltophilia. The percentage of residual pesticide remaining was determined by HPLC. The residual level of pesticide decreased with the prolonged incubation of microorganisms along with the pesticide and simultaneously the percentage of degradation also increased gradually indicating that the selected microorganisms were capable of degrading the pesticide, lambda cyhalothrin. Due to their high biodegradation activity, the bacteria isolated from this work merit further study as potent biological agents for the remediation of soil or water contaminated with the pesticide Lambda cyhalothrin
