Bacillus sphaericus is an ubiquitous, cosmopolitan, aerobic, spore-forming bacteria. Nine serotype strains among them are pathogenic for mosquito larvae. The most active strains produce a crystal toxin which is composed of two proteins of 51.4 and 41.9kD during sporulation. After larvae ingest the spore/crystal complex, the crystal toxin is hydrolyzed into active toxins and bind to a specific receptor on midgut brush-border membranes. The resulting damage of the midgut cells leads to the death of mosquitoes. During the vegetative growth, the low toxic and some high toxic strains synthesize mosquito-larvicidal proteins of 100, 31.5 and 35.8kD(Mtx toxins). It is proved that these toxins have no homology with the crystal toxin and other insecticidal toxins. For better control of mosquito larvae, cloning and expressing of the crystal and Mtx toxin genes in different hosts have been studied. In this paper, the recent progress and development on mosquito-larvicidal toxins of B.sphaericus and their genetic manipulation for mosquito control are reviewed.
展开▼
