Abstract
Development of resistance in major stored grain pests to the key fumigant phosphine across the globe has threatened its status as a reliable fumigant. It is urgent to find alternative approaches to control stored grain pests. Knowledge about the mechanism of phosphine resistance will help develop novel pest control strategies. Many studies have shown that symbiotic microbes have positive impacts on host pesticide resistance. As Escherichia coli was isolated from the gut of one strain of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in our previous study, here we isolated E. coli from phosphine-resistant T. castaneum in order to clarify its relationship with phosphine resistance of T. castaneum. A strain of E. coli isolated from the gut of phosphine-resistant adult T. castaneum significantly increased phosphine resistance of adult T. castaneum. Phosphine exposure had negative transgenerational effects on population fitness and decreased the content of phosphocholine (PC) and phosphatidylethanolamine (PE) of T. castaneum. Inoculation of sterile beetles with E. coli improved population fitness and increased the content of PC, PE, and total lipids of T. castaneum, especially in the presence of phosphine. These results suggest that E. coli increases phosphine resistance of T. castaneum by improving its population fitness, and lipid metabolism regulated by E. coli may play a very important role in it. Further study on the physiological mechanisms that underlie how E. coli regulates host lipid metabolism will help reveal the mechanism of phosphine resistance of T. castaneum.
