A Biofilm-State Bacillus thuringiensis Formulation Drives Midgut Structural Disruption and Transcriptomic...

Area of Science:

• Microbial Insecticides
• Bacterial Physiology
• Insect Pathology

Background:

• Bacillus thuringiensis (Bt) is a widely used microbial insecticide targeting insect midgut epithelium via Cry toxins.
• Bt's efficacy is influenced by its physiological state and host gut environment, with biofilm formation being a key adaptive strategy.
• The impact of Bt's biofilm state on host responses at structural and transcriptomic levels remains poorly understood.

Purpose of the Study:

• To evaluate the insecticidal efficacy of biofilm-state Bt formulations.
• To investigate the synergistic effects of biofilm inducers with Bt.
• To elucidate the structural and transcriptomic alterations in the host insect midgut upon exposure to biofilm-state Bt.

Main Methods:

• Bioassays were conducted using Ectropis grisescens neonate larvae exposed to biofilm-state Bt and planktonic Bt.
• A biofilm inducer system (Tween-80, tea saponin, matrine, tea polyphenols) was employed.
• Histopathological, biochemical, and transcriptomic analyses were performed on insect midguts.

Main Results:

• Biofilm-state Bt with composite inducers significantly increased corrected mortality and reduced LC50 by 2.88-fold compared to planktonic Bt.
• Histopathological analysis revealed more severe midgut damage caused by biofilm-state Bt.
• Transcriptomic analysis indicated extensive remodeling of detoxification and stress-response pathways in the host.

Conclusions:

• Bacterial physiological state, specifically biofilm formation, is a critical factor determining Bt formulation efficacy.
• Optimizing Bt formulations through microbial physiological regulation, such as promoting biofilm formation, offers a novel strategy for enhanced pest control.
• This study provides a framework for developing more effective microbial insecticides by manipulating bacterial physiology.