Nematicidal Bacillus
thuringiensis Proteins?
Crystal proteins from the Gram-positive soil bacterium, Bacillus thuringiensis (Bt), are pore-forming toxins used extensively to control insect pests, but their effect on the invertebrate phylum Nematoda, which includes many soil dwelling species, has been under- investigated. However, researchers at the University of California, San Diego, are demonstrating that Bt crystal proteins are also toxic to nematodes. The group expressed seven different crystal toxin proteins from two largely unstudied Bt protein subfamilies and measured their toxicity on diverse free-living nematode species. They observed that four of these crystal proteins are active against multiple nematode species. Toxicity in nematodes correlated with damage to the intestine, consistent with the mechanism of crystal toxin action in insects. In addition, they showed that one novel nematicidal crystal protein can be engineered to a small 43-kDa active core. "Given the very low toxicity of Bt crystal proteins in general toward vertebrates, Bt crystal proteins may one day provide safe, cost-effective control of nematode parasites, such as those that infect over one quarter of the human population," conclude the researchers. (The Scientist, 2/18/03).
