The gut bacterium Serratia marcescens mediates detoxification of organophosphate pesticide in Riptortus pedestris by microbial degradation

Abstract Organophosphate insecticides have been widely used in agriculture to control insect pests and raised growing problems including insecticide resistance. According to recent studies, microbial symbionts play important roles in developing insecticide resistance. The bean bug Riptortus pedestris is a notorious pest of leguminous crops, harbouring diverse microorganisms in their insect midguts. However, the potential biological roles of many gut‐associated bacteria are largely unknown. In this study, we isolated a bacterial strain from the midgut of R. pedestris and identified it as Serratia marcescens based on its morphological characteristics and the phylogenetic analysis of the 16S rRNA gene sequence. A halo of phosphorus‐solubilizing bacteria was observed on a medium containing lecithin and an organophosphorus insecticide dimethoate. Subsequently, the microbial degradation of dimethoate was determined using Gas Chromatography with Mass Spectroscopy (GC–MS). Further analysis indicated that the S. marcescens contained organophosphorus‐degrading MBL‐fold metallo‐hydrolase gene. Additionally, we discovered that the bacterium could colonize the insect midgut stably and enhance the host survivorship when exposed to dimethoate. Our results revealed that an insect gut‐associated bacterium could degrade organophosphorus compounds, thereby reducing related insecticide toxicity to the insect hosts. These findings provided further insights into the host‐microbiota interactions underpinning the development of insecticide resistance.