Expression of Bacillus thuringiensis mosquitocidal toxin in an antimicrobial Bacillus brevis strain

Brown blotch is a common disease of many mushrooms, especially oyster mushrooms, in Korea. Recently, we isolated a promising Bacillus brevis strain which has antimicrobial activity against Pseudomonas tolaasii, a serious mushroom pathogen. In this study, in order to confer insecticidal activity, a recombinant B. brevis strain was constructed via the expression of Bacillus thuringiensis mosquitocidal crystal protein. A B. thuringiensis expression vector (pPro11A), which contained the cry11Aa gene under the control of cry1Ac promoter, was introduced into this B. brevis strain. The recombinant B. brevis strain successfully expressed and produced rhomboidal shaped Cry11A protein, although the initiation time of expression was slower than that of B. thuringiensis Cry-B transformant. The insecticidal and antimicrobial activities of the transformant were verified using two dipteran larvae, Aedes aegypti and Culex pipiens, and four bacteria, including P. tolaasii, respectively. These results demonstrate that the introduction of B. thuringiensis insecticidal activity to antimicrobial Bacillus strains might be a useful tool to construct dual functional Bacillus strains.