Related Experiment Videos
Localization of a mosquito-larval toxin of Bacillus sphaericus 1593
Abstract:
Cell-free wall, membrane, and cytoplasmic fractions were prepared from Bacillus sphaericus 1593, which exhibited toxic activity against larvae of the mosquito Culex pipiens var. quinquefasciatus. Breakage of 12- to 14-h cells by sonication or French pressure cell yielded toxic material which could be assayed in a standard mosquito larva bioassay. When sporulating cells of strain 1593 were fractionated, the majority of the toxic activity was localized in the cell wall rather than in the plasma membrane or cytoplasm. The toxin located in the bacterial cell wall was relatively stable, in that activity was unaffected by treatment with trypsin, pronase, CHCl3-CH3OH-water, Triton X-100, 8 M urea (30 min), heat (80 degrees C, 12 min), sonication, refrigeration, lyophilization, or freezing. Activity was destroyed by boiling for 10 min or by 0.01 N NaOH. Only about 1.0% of the activity present in purified cell walls could be recovered by a 2-h extraction with 8 M urea or 3 M guanidine hydrochloride. A comparison of the toxicity of a cell-free cell wall fraction with that of a sample consisting entirely of heat-stable spores indicated that the spore preparation was about 10 times more active.
Insights
Bacillus sphaericus 1593 cell walls contain a mosquito larvicide. This bacterial toxin is stable but less potent than heat-stable spores, offering potential for mosquito control.
Area of Science:
- Microbiology
- Insect Toxicology
- Biochemistry
Background:
- Bacillus sphaericus produces toxins targeting mosquito larvae.
- Understanding toxin localization and stability is crucial for developing effective biocontrol agents.
Purpose of the Study:
- To investigate the cellular localization and stability of the toxic activity in Bacillus sphaericus 1593 against Culex pipiens var. quinquefasciatus larvae.
Main Methods:
- Preparation of cell-free fractions (cell wall, membrane, cytoplasm) from Bacillus sphaericus 1593.
- Mosquito larva bioassay to determine toxic activity.
- Stability assays involving various chemical and physical treatments (enzymes, detergents, solvents, heat, pH).
Main Results:
- The majority of toxic activity was localized in the cell wall fraction.
- The cell wall-associated toxin exhibited remarkable stability against trypsin, pronase, organic solvents, detergents, 8 M urea, heat (80°C), sonication, and freezing.
- Toxin activity was lost upon boiling or treatment with 0.01 N NaOH.
- Extraction with 8 M urea or 3 M guanidine hydrochloride yielded minimal toxin recovery.
- Heat-stable spores were approximately 10 times more toxic than the cell wall fraction.
Conclusions:
- The cell wall of Bacillus sphaericus 1593 harbors a relatively stable insecticidal toxin.
- The toxin's stability suggests potential for formulation and application in mosquito control programs.
- Further research may focus on enhancing the potency of the cell wall-derived toxin or utilizing spore-based formulations.