Abstract
The intensive and extensive application of imidacloprid in agriculture has resulted in water pollution and risks to aquatic invertebrates. However, pure bacteria remediation of imidacloprid in surface water environments has not been studied. Here, we isolated an imidacloprid-degrading bacterium from a water environment, examined its imidacloprid degradation in pure culture and surface water, sequenced its genome, and compared its Clusters of Orthologous Groups (COG) protein categorization with that for another imidacloprid-degrading bacterium. The isolate was an obligate oligotrophic bacterium, Hymenobacter latericoloratus CGMCC 16346, which degraded imidacloprid via hydroxylation by co-metabolism in pure culture. Resting cells degraded 64.4% of 100 mg/L imidacloprid in 6 days in the presence of co-substrate maltose, and growing culture degraded 40.8% of imidacloprid in 10 days. H. latericoloratus CGMCC 16346 degraded imidacloprid in surface water without co-substrate supplementation and retained imidacloprid-degrading activity after 30 days. The half-life of imidacloprid in surface water was decreased from 173.3 days in the control to 57.8 days by CGMCC 16346 inoculation. Genome sequencing and COG analysis indicated that carbohydrate metabolism and transport, cell wall/membrane biogenesis, and defense mechanisms are enriched in H. latericoloratus CGMCC 16346 compared with the copiotrophic imidacloprid-degrading Pseudoxanthomonas indica CGMCC 6648, indicating that H. latericoloratus CGMCC 16346 is adapted to live in oligotrophic water environments and biofilms. H. latericoloratus CGMCC 16346 is a promising bioremediation agent for elimination of imidacloprid contamination from surface water.
Highlights
Imidacloprid (N-{1-[(6-chloro-3-pyridyl)methyl]-4,5-dihydroimidazol-2-yl}nitramide) is a systemic neonicotinoid insecticide that acts on the central nervous system of pest insects
Isolation of imidacloprid‐degrading microbe and taxonomic identification About 200 colonies grown on Mineral salt medium (MSM) agar were streaked onto Reasoner’s 2A (R2A) plates and eight different bacterial morphologies were observed among the growing colonies
Addition of 1% co-substrate maltose did not enhance imidacloprid degradation compared with the control without maltose addition. These results indicated that H. latericoloratus CGMCC 16346 could degrade imidacloprid in surface water and co-substrate had no effect on the imidacloprid remediation
Summary
Imidacloprid (N-{1-[(6-chloro-3-pyridyl)methyl]-4,5-dihydroimidazol-2-yl}nitramide) is a systemic neonicotinoid insecticide that acts on the central nervous system of pest insects. Recent surveys of imidacloprid detection from the USA, Netherlands, Australia, Sweden, Vietnam and China have confirmed water contamination by imidacloprid (Lamers et al 2011; van Dijk et al 2013; Morrissey et al 2015). In these surveys, imidacloprid residues were detected in 78–100% of cases in surface waters at concentrations often exceeding the benchmarks for protection of aquatic organisms in the respective countries. Klarich et al (2017) found the presence of imidacloprid in finished drinking water, demonstrating its persistence during conventional water treatment
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