روش انتخابي براي جدا نمودنBacillus thuringiensis از خاك و اثر توكسين توليدي آن بر روي Musca Domestica

Selective process for efficient isolation of soil Bacillus thuringiensis and measurment of its toxin effect on common Musca domestica

Bacillus thuringiensis , which was shown to have a great potential for pest control, have been subjected to many studies , because of its toxin production. The aim of this research was to consider if a biological product can be used as an insecticide. We were able to isolate Bacillus thuringiensis from environmental soil samples 20 different isolates were identified on the basis of the results of characterization and antibiotic sensitivity tests, with plasmid sizes differed from 1.8 to 74.6 kbp . In our process , germination of Bacillus thuringiensis spores was selectively inhibited by sodium acetate, while most of undesired sporeformers germinated .Next, all of the nonsporulated microbes were eliminated by heat treatment on 80 0C for 3 minutes .The surviving spores were then plated on a rich agar medium, and allowed to grow until sporulation. Of random colonies picked from agar , 96% were crystal forming Bacillus thuringiensis. At the final step, toxins were extracted from Bacillus thuringiensis and effects of the toxins were examined on larvae of common Musca Domestica .According to the results of this assay, Bacillus thuringiensis and its endotoxin was shown to be effective on larvae of the tested insect,and so can be used as an insecticide.