Comparison of the co-occurrence patterns of the gut microbial community between Bt-susceptible and Bt-resistant strains of the rice stem borer, Chilo suppressalis

Bacillus thuringiensis (Bt), an effective entomopathogen, has been widely used for pest control. However, insect resistance risk threatens the sustainable utility of Bt products. Previous findings suggest the interactions between gut microbiota and the host probably influence the evolution of insect resistance. To understand how the microbiota affects the development of insect resistance and manage the resistance, we characterized the gut microbiota of Chilo suppressalis from five Bt-resistant or Bt-susceptible strains by 16S rRNA sequencing. The diversity, richness, and composition of gut microbial community were analyzed among these five strains by alpha and beta analyses. Gut microbiota diversity was significantly higher in Bt-resistant (BJ1Ab-R and FZ1Ca-R) than that in Bt-susceptible strains (BJ-S and FZ-S). A significantly higher abundance of the genus Enterococcus were found in BJ-S- and FZ-S-susceptible strains than that in BJ1Ab-R- and FZ1Ca-R-resistant strains. The genus Bifidobacterium significantly dominated in the FZ1Ca-R-resistant strain, compared with the other four strains. Moreover, the gut microbial community displayed significantly more complex cooccurrence patterns in Bt-resistant than in Bt-susceptible strains by network analysis. Furthermore, the BJ-S, FZ-S and FZ1Ca-R strains had significantly reduced larval mortalities in bioassays with Bt toxin after larval pretreatment with antibiotics to remove gut bacteria. This study suggests that the gut microbiota participates in regulating the Bt-induced killing mechanism in C. suppressalis, and provides insights into the impact of Bt selective pressure on microbiome composition and potential insect resistance induced by microbiome alterations. [GRAPHICS] .