Differential Characterization of Midgut Microbiota Between Bt-Resistant and Bt-Susceptible Populations of Ostrinia furnacalis

<i>Bacillus thuringiensis</i> (Bt) is an efficacious biocontrol bacterium known for producing various toxins, such as crystal toxins, which disrupt the midgut epithelium of pest larvae, leading to larval mortality. However, the development of resistance to <i>Bacillus thuringiensis</i> in pests poses a significant threat to the widespread application of Bt corn. Consequently, we employed high-throughput sequencing of the midgut bacterial 16S ribosomal RNA to characterize the midgut bacteria in four Bt-resistant strains. Specifically, Bt-resistant strains (ACB-FR and ACB-AcR) exhibited lower bacterial diversity compared to ACB-AbR and ACB-IeR. Multivariate analyses and statistical evaluations further demonstrated that the microbiota communities in Bt-resistant pests (AbR, AcR, IeR, and FR) were distinct from those in Bt-susceptible strains. Notably, the genus <i>Klebsiella</i> predominated in BtS, whereas <i>Enterococcus</i> was the genus with peak enrichment in AbR, AcR, IeR, and FR. Bioassays subsequently revealed that <i>Enterococcus</i> enhances the Cry1Ab resistance of ACB larvae. Our investigations indicate that treatment with Bt protein alters the midgut microbiota community of <i>O. furnacalis</i>, and these microbiota differences may potentially modulate the Bt-induced lethality mechanism.