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Survival and conjugation of Bacillus thuringiensis in a soil microcosm
Vilas-Bôas1, Vilas-Bôas, Saridakis
1Bio/CCB, Universidade Estadual de Londrina 86051-970, Londrina, Brazil
Abstract:
The survival and conjugation ability of sporogenic and asporogenic Bacillus thuringiensis strains were investigated in broth, in non-amended sterile clay soil monoculture and in mixed soil culture. The 75 kb pHT73 plasmid carrying an erythromycin resistance determinant and a cry1Ac gene was transferred in mating broth and soil microcosm. Survival of strains was assessed in soil monoculture and in mixed soil culture for up to 20 days. Sporogenic strains rapidly formed viable spores which were maintained until the end of the experiment. The asporogenic strains were no longer recovered after 8 days of incubation. This study shows that the environmental impact of asporogenic B. thuringiensis strains is lower than that of sporogenic B. thuringiensis strains. Thus, the use of asporogenic strains may significantly reduce any potential risk (gene transfer, soil and plant contamination) due to the dissemination of B. thuringiensis-based biopesticides in the environment.
Insights
Asporogenic Bacillus thuringiensis strains have a lower environmental impact than sporogenic strains. Using asporogenic strains can reduce risks associated with biopesticide use, such as gene transfer and contamination.
Area of Science:
- Environmental microbiology
- Agricultural biotechnology
- Bacterial genetics
Background:
- Bacillus thuringiensis (Bt) is widely used as a biopesticide.
- Understanding the environmental fate of Bt strains is crucial for risk assessment.
- Sporogenic and asporogenic Bt strains differ in their survival and ecological behavior.
Purpose of the Study:
- To compare the survival and conjugation ability of sporogenic and asporogenic Bt strains in soil.
- To assess the environmental persistence and gene transfer potential of different Bt strains.
- To evaluate the ecological impact of using asporogenic Bt strains in biopesticides.
Main Methods:
- Investigated survival of sporogenic and asporogenic Bt strains in broth, sterile clay soil monoculture, and mixed soil.
- Assessed plasmid transfer (75 kb pHT73 with erythromycin resistance and cry1Ac gene) in broth and soil microcosms.
- Monitored strain recovery over 20 days in soil environments.
Main Results:
- Sporogenic Bt strains formed persistent, viable spores in soil.
- Asporogenic Bt strains were not recovered after 8 days of incubation.
- Plasmid transfer was observed in both broth and soil microcosms.
Conclusions:
- Asporogenic Bt strains exhibit significantly lower environmental persistence compared to sporogenic strains.
- The use of asporogenic Bt strains may mitigate environmental risks associated with biopesticide dissemination.
- Reduced survival of asporogenic strains lowers the potential for gene transfer and soil/plant contamination.