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Alteration in Bacillus thuringiensis toxicity by curing gut flora: novel approach for mosquito resistance management
Chandrashekhar D Patil1, Hemant P Borase, Bipinchandra K Salunke
1School of Life Sciences, North Maharashtra University, Post Box 80, Jalgaon, 425001, Maharashtra, India.
Abstract:
Mosquitoes are known for acquiring resistance against insecticides in many ways, namely target side mutation, enzyme modification, sequestration, quick elimination, etc. But, the role of microflora present in abundance in the larval midgut is less explored with respect to their role in insecticide resistance. During the course of their development, mosquitoes are continuously exposed to microbes and have naturally acquired midgut microbial flora. This midgut flora can modulate the mosquito's susceptibility to Bacillus thuringiensis (Bt) infection by degrading toxic Bt protein forms through an unknown mechanism. In this study, we show that microbe-free aseptic mosquito larvae displayed an increased susceptibility to Bt toxicity compared to larvae harboring natural microbial flora. Fourth instar larvae of Anopheles stephensi were treated separately with penicillin, streptomycin, erythromycin (100 μg/ml), and mixtures of all three antibiotics and then analyzed for Bt toxicity. We have also examined the influence of the mosquito's midgut microbial flora under microaerophilic condition on the Bt protein degradation through plate, broth, TLC, and UV-vis spectrophotometric assay. A better understanding of the roles of microbiota in preventing Bt toxicity to mosquitoes could potentially lead to the development of new sustainable mosquito control strategies.
Insights
Mosquito gut microbes protect larvae from Bacillus thuringiensis (Bt) toxicity. Removing these microbes increases mosquito susceptibility to Bt, suggesting a novel avenue for mosquito control strategies.
Area of Science:
- Entomology
- Microbiology
- Toxicology
Background:
- Mosquitoes develop insecticide resistance through various mechanisms.
- The role of larval midgut microflora in insecticide resistance is underexplored.
- Midgut microbes may influence mosquito susceptibility to Bacillus thuringiensis (Bt).
Purpose of the Study:
- To investigate the role of mosquito midgut microbial flora in modulating susceptibility to Bacillus thuringiensis (Bt) toxicity.
- To explore the mechanism of Bt protein degradation by midgut microbiota.
Main Methods:
- Aseptic rearing of Anopheles stephensi larvae.
- Antibiotic treatment (penicillin, streptomycin, erythromycin) to deplete midgut flora.
- Assessment of Bt toxicity in microbe-free vs. naturally colonized larvae.
- Microbial degradation assays (plate, broth, TLC, UV-vis spectrophotometry) under microaerophilic conditions.
Main Results:
- Microbe-free larvae showed significantly increased susceptibility to Bt toxicity compared to larvae with natural flora.
- Evidence suggests midgut microbes degrade Bt proteins, reducing toxicity.
- Specific microbial degradation of Bt toxins was confirmed through various assays.
Conclusions:
- Larval midgut microbiota plays a crucial protective role against Bacillus thuringiensis toxicity in mosquitoes.
- The degradation of Bt toxins by gut microbes is a key mechanism of this protection.
- Harnessing mosquito microbiota could lead to innovative and sustainable mosquito control strategies.
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