Biotoxicity assay of Bacillus thuringiensis (spores) against Tribolium castaneum

Bacillus thuringiensis spore forming, gram positive aerobic bacteria whose spores consist of the crystal proteins, are found to have the insecticidal activity to the specific insect orders. B. thuringiensis are considered to be cosmopolitan in nature and a great difference occurs between the two strains from different habitat. The present study was conducted on the collection of samples and isolation of the B. thuringiensis from different samples. These isolates were identified on the basis of microscopic and staining techniques. Culturing of these isolates was made on the specific media such as T3. Culturing of these bacteria was done to get enough amount of the B. thuringiensis spore cell. Rearing of the Tribolium castaneum a flour beetle was done by understanding the physiology of the beetles. Then biotoxic effect of these bacteria was determined by the process of Biotoxicity assay of the B. thuringiensis spores against T. castaneum in glass vials in triplicates. The seven day repeated observation of these isolates was presented in the tabular form and LC50 was calculated by the Probit analysis programme. LC50 vary from isolate to isolate for the insect under consideration, giving different mortality rates.