Prospects of Plant Growth Promoting Bacteria, Bacillus megaterium for the Biodegradation of Selected Novel Pesticides

Abstract

Thiamethoxam and chlorantraniliprole, the systemic novel insecticides, are applied as granular, and foliar formulations for insect pest control. The present study evaluated the potential of Bacillus megaterium for bioremediation of these novel pesticides in natural and amended soils. The survivability of B. megaterium was studied in liquid half-strength nutrient broth supplemented with thiamethoxam or chlorantraniliprole in the concentration range of 5-100 mg/L. In addition, soil microcosm studies were conducted (21 days) to explore the bio-stimulating effect on degradability in pesticide-treated soils (@ 10 mg/kg) when B. megaterium is used along with organic amendments viz., vermicompost and Vesicular Arbuscular Mycorrhiza (VAM) and degradation half-lives were estimated based on their residual concentrations using an HPLC-PDA.

B. megaterium could grow in half-strength nutrient broth supplemented with thiamethoxam or chlorantraniliprole with maximum optical density of 0.734 AU and 0.965 AU observed at 100 mg/kg for thiamethoxam and chlorantraniliprole, respectively and also exhibited colony-forming units (20-40 x 10⁵) when plated on the nutrient agar indicating its survivability. Soil application of B. megaterium combined with vermicompost or VAM has reduced the half-life for both thiamethoxam and chlorantraniliprole (11 to 18 days) compared to natural attenuation (29 - 35 days). The enzymatic activity was negatively impacted for all the enzymes under study in treatments compared to the control