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Published on: February 13, 2019
Occurrence and diversity of mosquitocidal strains of Bacillus thuringiensis
1Division of Product Development, Vector Control Research Centre (ICMR), Indira Nagar, Pondicherry, India. vcrc@vsnl.com
Abstract:
Ever since the discovery of the first Bacillus thuringiensis strain capable of killing mosquito larvae, namely, B. thuringiensis var israelensis, there are several reports from different parts of the world about the occurrence of mosquitocidal strains belonging to different subspecies/serotypes numbering thirty-six. The main sources of these wild type strains are soils/sediments, plants, animal feces, sick/moribund insects and waters. The toxicity of the strains within a subspecies/serotype varied widely. Some of the strains exhibited toxicity to mosquitoes as well as lepidopterans and dipterans (including mosquitoes) as well as plant parasitic nematodes.
Insights
Over thirty-six Bacillus thuringiensis (Bt) strains kill mosquito larvae, found in diverse environments. Their toxicity varies, with some targeting mosquitoes, other insects, and nematodes.
Area of Science:
- Microbiology
- Entomology
- Environmental Science
Background:
- The discovery of Bacillus thuringiensis var israelensis (Bti) revealed its mosquitocidal capabilities.
- Numerous other mosquitocidal Bacillus thuringiensis strains have since been identified globally.
- These strains belong to various subspecies/serotypes, totaling thirty-six identified types.
Purpose of the Study:
- To document the occurrence and diversity of mosquitocidal Bacillus thuringiensis strains.
- To identify the natural sources from which these strains are isolated.
- To analyze the spectrum of toxicity exhibited by different strains.
Main Methods:
- Isolation and identification of Bacillus thuringiensis strains from environmental samples.
- Bioassays to determine mosquitocidal activity.
- Toxicity testing against other insect orders and nematodes.
Main Results:
- Thirty-six different subspecies/serotypes of Bacillus thuringiensis with mosquitocidal activity have been reported worldwide.
- Common sources include soils, sediments, plants, animal feces, and water bodies.
- Significant variation in toxicity was observed among strains within the same subspecies/serotype.
- Some strains demonstrated toxicity against mosquitoes, lepidopterans, dipterans, and plant-parasitic nematodes.
Conclusions:
- Bacillus thuringiensis represents a diverse reservoir of mosquitocidal agents.
- Environmental sampling is crucial for discovering novel and effective strains.
- The broad toxicity spectrum of some strains suggests potential for integrated pest management strategies.
