Egyptian researchers discovered a powerful strain of the pesticide Bt in the dead larvae of the pink boll weevil. Egyptian scientists have discovered a strain of the popular bio-pesticide Bacillus thuringiensis, which they say will be able to kill more pests than any other strain of the bacterium without harming beneficial insects.

The new strain of Bacillus thuringiensis, commonly called Bt, was found in the dead larvae of the pink boll worm, the most harmful insect to cotton crops. The research, which was conducted at the Agricultural Genetic Engineering Research Institute in Giza, Egypt, is being reported in the June 19 issue of New Scientist.

Until now, each strain of Bt produced toxins that affected a certain insect. For instance, Bt strains developed for mosquito larvae do not affect caterpillars. The multi-talented Egyptian strain produces 18 toxins that has been shown to kill moths, coleopteran beetles, two-winged insects like mosquitoes and nematode worms.

"We were amazed and very happy when we stumbled on it," Yehia Osman, head of the research team that isolated the bacterium at told New Scientist. "This is the most potent Bt strain yet found and it has the most diversified host range."

Osman presented his findings earlier this month at the annual meeting of the Society for Microbiology in Chicago.

Bt is a soil-based naturally occurring bacterium that has been used as an organic pesticide by farmers for the past 30 years. Bt kills insects by producing proteins that react with cells that line the gut of susceptible insects. These proteins arrest the insects' digestive system and it stops feeding within hours.

Occasionally, Bt enters the blood stream and reproduces inside the insect. Scientists found that the dead bacteria contained the proteins and remained effective as insecticides.

The safety of Bt has been a recent topic of concern. French researchers found that mice contracted fatal lung infections after inhaling the bacteria. And Azam Tayabali of the Canadian health ministry reported at the same Chicago meeting results of a study that showed bacterial spores in some commercial Bt strains can kill human cells. He suggested farmers wear protective gear when spraying the pesticide.

Osman and his colleagues refute these reports and insist their studies show Bt is safe for organic farming. "We've done toxicity tests in rats and fish and didn't get any adverse effects at all," Osman told New Scientist.

The institute patented some of the important genes that make the toxin and has an agreement with Pioneer Hi-Bred, a seed company in Iowa, to potentially license use of the genes in genetically modified crops.

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