Evaluation of different methods for isolation of Bacillus thuringiensis from soil samples

Background and Aim : Bacillus thuringiensis is the most known environment-friendly biopesticide. Various methods were performed for the isolation of Bt from different types of samples. High-performance methods with different principles are needed because a single method is not suitable for isolating organisms from various environments. Currently, obtaining an effective isolation method is a challenge.Methods : In this study, ۶۰ soil samples from the south of Iran were collected. The efficiency of four methods in isolation of Bt was evaluated. The number of samples in which Bt colonies were found was used to determine each method’s efficiency. Four methods were the dry heat pretreatment method, heat shock method, sodium acetate selection method, and the isolation of Bt using the M۹ medium supplemented with L-serine.Results : Bt was isolated from ۲۳, ۱۸, ۱۲, and ۳۵ samples using the dry heat pretreatment method, heat shock method, sodium acetate selection method, and M۹ medium supplemented with L-serine method, respectively. Conclusion : In this research, the efficiency of standard methods in isolation of Bt was examined. The results reveal that the M۹ medium supplemented with L-serine has minor errors and a higher rate of Bt isolation. This method showed ۳۴%, ۴۹%, and ۶۹% more efficiency than the dry heat pretreatment method, heat shock method, and sodium acetate selection method isolation of Bt colonies, respectively. Despite its limitations, the finding has important results for future practices to optimize and devise methods to improve the isolation of Bt from various samples.

کلیدواژه ها:

Bacillus thuringiensis ، Soil ، Isolation ، Biopesticide ، Biocontrol