Diversity and functional profile of gut symbiotic bacteria between Lysinibacillus sphaericus C(3)-41 susceptible and resistant Culex quinquefasciatus Say as revealed by 16S rRNA gene high-throughput sequencing

Previous studies have demonstrated that symbiotic gut bacteria in insects are involved in the development of insecticide resistance, but the relationship between the symbiotic gut bacteria and resistance to Lysinibacillus sphaericus C(3)-41 in Culex pipiens quinquefasciatus remains unclear. In this study, the abundance and diversity of gut symbionts of Cx. quinquefasciatus that were resistant (RLCql) or susceptible (SLCql) to L. sphaericus C(3)-41 were analyzed by high-throughput 16S rRNA sequencing. The main phyla among the symbiotic gut bacterial communities of Cx. quinquefasciatus were Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes. However, the relative abundance of Firmicutes, Proteobacteria, and unidentified Bacteria in the gut of the resistant strain of Cx. quequinfasciatus (RLCql colony) was higher compared to the susceptible strain (SLCql colony). The NMDS (Non-Metric Multi-Dimensional Scaling) and unweighted unifrac PCoA analyses also revealed significant differences between the symbiotic gut bacterial communities from the resistant and susceptible strains, suggesting that bacterial insecticides can alter bacterial composition. Ultimately, the changes in the bacterial community likely occurred after the development of resistance to L. sphaericus C(3)-41. These results provide guidance for further research into the mechanisms of gut symbionts involved in resistance against L. sphaericus C(3)-41 in Cx. quinquefasciatus.