Degradation of Imidacloprid in Liquid by Enterobacter sp. Strain ATA1 Using Co-Metabolism

Imidacloprid (IMI), a potent insecticide, belongs to the neonicotinoid family and is of great concern due to the fact that its persistence in the soil is a threat to both plants and vertebrates. The present study was aimed at the isolation and characterization of a bacterial strain from paddy field soil at Punjab (India), which has a history of 9–10 years of imidacloprid contamination. Among the various isolates, a soil bacterium was selected and identified by 16S rRNA gene sequencing as Enterobacter sp. strain ATA1. It grew well in pH ranging from 6.0 to 7.0 at 37°C, and it was found to be a competent bacterium for the degradation of IMI. The presence of glucose in minimal salt medium (MMG; 0.1% w/v) as compared with any other co-substrate provokes the dissipation of IMI as a co-metabolite. Initially, incubation of IMI for 72 h in the MMG resulted in 30–40% degradation; thereafter, no significant change in its amount was found until 15 days of incubation, which explains the disappearance of any viable cells in the medium. Among the various identified metabolites, imidacloprid urea (m/z = 212) and imidacloprid guanidine (m/z = 211) were found to be the end products of IMI degradation, whereas others remained unidentified (m/z = 99 and m/z = 119).