Co-metabolic transformation of the neonicotinoid insecticide imidacloprid by the new soil isolate Pseudoxanthomonas indica CGMCC 6648
A new imidacloprid (IMI) degrading bacterium Z-9 (deposited number CGMCC 6648) was isolated and identified as Pseudoxanthomonas indica by 16S rRNA gene analysis. Two metabolites were identified as olefin and 5-hydroxy IMI by liquid chromatography-mass spectrometry and nuclear magnetic resonance analysis. P. indica CGMCC 6648 degraded 70.1% of IMI (1.22 mmol L−1) and formed 0.93 mmol L−1 5-hydroxy IMI and 0.05 mmol L−1 olefin IMI in 6 days and in the presence of 100 mmol L−1 glucose. The half-life of IMI degradation was 3.6 days. P. indica CGMCC 6648 transforms IMI via a co-metabolism mechanism and different carbohydrates have significant effects on 5-hydroxy IMI formation, whereas different organic acids have substantial effects on olefin IMI production. Lactose is the best co-substrate for IMI degradation and 5-hydroxy IMI formation with 0.77 mmol L−1 degraded and 0.67 mmol L−1 formed in 48 h, respectively. Pyruvate is the best co-substrate for olefin IMI formation with 0.17 mmol L−1 produced in 96 h for all carbon sources tested. Pyruvate significantly stimulates the conversion of 5-hydroxy IMI to olefin IMI, whereas glucose slightly inhibits this reaction. P. indica CGMCC 6648 rapidly degrades IMI and forms olefin IMI, which may enhance its potential for biodegradation of IMI and increase its insecticidal activity, which can decrease the IMI dosage required.