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Isolation and curing of plasmid DNA from Bacillus thuringiensis israelensis strains showing variable insecticidal
1Department of Entomology, Faculty of Science, Ain Shams University, Cairo.
Abstract:
Bacillus thuringiensis israelensis 4Q1-WT (B.t.i.) have 9 plasmids. Fourteen mutates of this wild type were prepared with cured plasmids. The wild bacterial strain the mutants and fourteen industrial strains were compared according to the number, size of plasmids and their potential to induce mortality to Aedes caspius larvae. The 108 Kb plasmid is essential for B.t israelensis to induce insect kill.
Insights
Bacillus thuringiensis israelensis (B.t.i.) requires a specific 108 Kb plasmid to effectively kill Aedes caspius mosquito larvae. Researchers compared wild strains, mutants, and industrial strains to identify this essential genetic component for insecticidal activity.
Area of Science:
- Microbiology
- Molecular Biology
- Insecticide Development
Background:
- Bacillus thuringiensis israelensis (B.t.i.) is a bacterium utilized as a biological larvicide.
- The insecticidal properties of B.t.i. are attributed to plasmids encoding toxic proteins.
- Understanding the role of specific plasmids is crucial for optimizing B.t.i. efficacy.
Purpose of the Study:
- To investigate the role of plasmids in the insecticidal activity of Bacillus thuringiensis israelensis against Aedes caspius larvae.
- To compare wild-type B.t.i. strains, plasmid-cured mutants, and industrial strains.
- To identify the specific plasmid essential for B.t.i. larvicidal activity.
Main Methods:
- Generation of fourteen plasmid-cured mutants from the wild-type B.t.i. 4Q1-WT strain.
- Analysis of plasmid profiles (number and size) in wild-type, mutant, and industrial B.t.i. strains.
- Bioassays to determine the mortality rate induced in Aedes caspius larvae by different strains.
Main Results:
- The wild-type B.t.i. 4Q1-WT strain possesses 9 plasmids.
- Plasmid profiles varied among the wild-type, mutant, and industrial strains.
- The 108 Kb plasmid was identified as indispensable for B.t.i. to induce mortality in Aedes caspius larvae.
Conclusions:
- A specific 108 Kb plasmid is essential for the larvicidal activity of Bacillus thuringiensis israelensis.
- The presence and characteristics of plasmids significantly influence the insecticidal potential of B.t.i.
- This finding aids in the development of more effective microbial insecticides.