Abstract：Caenorhabditis elegance is one of the model organisms that could be raised with Escherichia coli in lab. Crystal proteins from B. thuringiensis are pore-forming toxins used as insecticides around the world . A collection of Bt strains were screened for toxic activity against the nematodes .Six strains were identified with significant toxicity to the adult nematodes in vitro. By assaying their toxicity on free-living nematodes ， within 36 hours ， the LC50 of the nematicidal toxins achieved 0.498 µg/ml . It’s concluded that Bt crystal proteins have potential in controlling nematodes . Toxic proteins were purified crudely by sulfate and the sizes were estimated by comparison with protein standards. DNA ladder survey showed that the toxic protein did not damage the DNA of nematodes as chemical pesticides.
