Expression and synergistic effect of three types of crystal protein genes in Bacillus thuringiensis.

Bacillus thuringiensis NT0423 newly isolated from sericultural farms in Korea produces quite atypical bipyramidal crystals of a common major band of ca. 130 kDa, and has dual specificity against Lepidoptera and Diptera. To enforce the Diptera toxicity of B. thuringiensis NT0423, cryIVD and cytA genes were transformed into B. thuringiensis NT0423. The transformant B. thuringiensis PT0529 was obtained from introduction of pCG5 into B. thuringiensis NT0423 by electroporation. The expression of crystal proteins in B. thuringiensis PT0529 was characterized by SDS-PAGE and electron microscopy. The results showed that crystalline inclusions of host, CryIVD and CytA were clearly observed in B. thuringiensis PT0529. Furthermore, the toxicity of B. thuringiensis PT0529 against Diptera was highly enforced by synergistic effect.