The crystal proteins - created by some strains of Bacillus thuringiensis, more commonly known as Bt - thwart the development of some nematodes and kill others outright. The findings raise the possibility that these proteins might one day be used to combat parasitic worms that infect nearly one-fourth of the world's human population. Nematodes - unsegmented, long, round worms pointed at both ends - are responsible for illnesses that can lead to elephantiasis of the limbs, intestinal lesions, a type of meningitis and "river blindness."

Led by biologist Raffi V. Aroian of the University of California San Diego, a team of researchers examined the impact of seven different Bt toxins upon six different nematode species, including one intestinal parasite. Funded by the National Science Foundation (NSF), the research appears in the March 4 journal Proceedings of the National Academy of Sciences (PNAS) and is available in the journal's online "early edition" at www.pnas.org.

The crystals, of which there are many variations, form from the aggregation of proteins that are produced as the bacillus makes spores. Individually, their toxicity is very species-specific, and more than 150 insect species are known to be susceptible to one type of Bt crystal or another. However, the crystals are harmless to humans and to natural enemies of many crop pests.

(For more about Bacillus thuringiensis, visit the Aroian lab's web site at www.btcrystal.org.)

Nematodes, relatively simple anatomically and genetically, are found in nearly every environment. Among the more than 100,000 known species are plant parasites, such as roundworms; animal parasites, such as hookworms
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Contact: Sean Kearns
skearns@nsf.gov
703-292-8070
National Science Foundation
6-Mar-2003