Identification and Characterization of Bacterial Isolates and their Role in the Degradation of Neonicotinoid Insecticide Thiamethoxam

Abstract

Thiamethoxam (THIA) degrading bacterial colonies were isolated from soil obtained from different ecosystems such as cotton, cabbage and paddy tolerating high concentrations of the insecticide followed by enrichment technique. Eight colonies were isolated and were morphologically and biochemically tested. Among eight bacterial isolates, three isolates named as THIA-3, THIA-4 and THIA-7 were found to be superior and recorded maximum growth in the medium supplemented with thiamethoxam as sole carbon source. Highest dissipation of thiamethoxam was recorded in the artificial medium inoculated with THIA-3 (94.72 %) followed by THIA-4 (90.78 %) and THIA-7 (82.06 %) compared to 53.85 percent in the control. In the thiamethoxam bioremediation study by using sterilized soil, half-life of thiamethoxam was reduced to 7.60 days in THIA-3 inoculation followed by THIA-4 (8.75 days) and THIA-7 (10.52 days) compared to 17.91 days in the control. The bacterial isolates viz., THIA-3, THIA-4 and THIA-7 were later identified as Acinetobacter sp., Enterobacter sp. and Bacillus sp., respectively through molecular characterization by 16S rRNA gene sequencing. These results highlight the potential of bacterial cultures to be used in the cleanup of pesticide contaminated sites in the environment.

Keywords

• enrichment
• dissipation
• 16s rrna
• acinetobacter sp.