Pseudomonas aeruginosa Y12 play positive roles regulating larval gut communities when housefly encountered copper stress

Heavy metal contamination has become a global concern that threatens the lives of animals and insects throughout the food chain. Pseudomonas is a commonly found genus of bacteria that colonizes the intestines of insects and constitutes a necessary part of the insect gut microbiota. This research analyzed the influence of different concentrations of Cu2+ on housefly larval development, gut microbial structure and antioxidant defense system, and investigated the regulatory mechanism of P. aeruginosa Y12 on the gut microbiota when houseflies were exposed to Cu2+. We found that adding Cu2+ to the larval diet inhibited larval growth, while the mixed addition of P. aeruginosa Y12 and Cu2+ to the diet reduced the inhibitory effects of Cu2+ on larval growth. Oral administration of Cu2+ significantly changed the gut community structure and increased larval gut bacterial diversity. In vitro analysis revealed that P. aeruginosa Y12 showed Cu2+ adsorption effects and increased Cu2+ aggregation. The mixed addition of low concentrations of P. aeruginosa Y12 and Cu2+ to the larval diet caused a dynamic shift in the gut microbiota and resulted in a novel gut community structure with an increase in beneficial bacteria and a decrease in pathogenic bacteria. Furthermore, P. aeruginosa Y12 treatment influenced the activity of antioxidant enzymes in housefly larvae, indicating that the addition of P. aeruginosa Y12 to the larval diet could further influence the antioxidant system through P. aeruginosa Y12-Cu2+ interactions. In conclusion, our research revealed that intestinal flora dysbiosis was the essential reason why copper inhibits housefly larval growth. However, proper supplementation with P. aeruginosa Y12 played positive roles in regulating larval gut communities and protecting insects from toxic heavy metals.