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Paper No. 349-6
Presentation Time: 9:00 AM-6:30 PM
BIOREMEDIATION OF TWO NEONICOTINOID INSECTICIDES, THIAMETHOXAM AND IMIDACLOPRID, USING SELECT BACTERIAL SPECIES
Neonicotinoid insecticides, thiamethoxam (THM) and imidacloprid (IMI), have become popular in the past decade since these show lower toxicity to birds and mammals compared to previously used insecticides. However, these appear to have detrimental effects, colony collapse disorder (CCD) in bees as well as developmental neurotoxicity in some species (Hyalella azteca, ostracod, and Chironomus riparius). Environmental persistence of these insecticides establishes the need to develop innovative and sustainable remediation techniques. The present study aims to fully characterize the comparative bioremediation potential of THM/IMI using Pseudomonas aeruginosa, Pseudomonas putida, Pseudomonas fluorescens, Alcaligenes faecalis, and Escherichia coli, Streptococcus lactis was used as a negative control. Phase I evaluated the utilization of THM and IMI (10-90mg/L) as the sole carbon (C) or nitrogen (N) source by P. aeruginosa, P. putida, and P. fluorescens. All three species used THM, but not IMI, as the sole C and N sources, and better growth was noted when THM was used as the sole N source. Phase II characterized the kinetics of THM removal from aqueous media by all six species. Results showed significant (p<0.0001) THM removal by E. coli (T50=12d), P. fluorescens (T50=18d), P. putida (T50=19d), and P. aeruginosa (T50=23d). Removal by A. faecalis (T25=17d) was slower, and S. lactis was minimal. THM removal showed a strong negative correlation (r2=0.98) with an unidentified metabolite in P. putida and P. fluorescens cultures. Ongoing phase III aims to identify the THM metabolites with E. coli, P. fluorescens, and P. putida, which were found to be most effective in THM removal to determine their relative toxicity compared to THM and to understand the true potential of THM bioremediation using these bacterial species. Results so far have shown two metabolites, one found in all three bacterial species (after 6days) and the other in P. fluorescens (after 14days).