The bacterium Bacillus anthracis (Ba) causes the deadly disease anthrax. Bacillus cereus (Bc) causes food poisoning. Bacillus thuriengiensis (Bt) is a natural pesticide. The three closely related bacteria all live in the soil and may be considered a single species. They readily crossbreed, swapping viruses and genetic material. Previous warnings from the Institute of Science in Society that dangerous recombinants (hybrids) may emerge have now been realised.

In 2003 Claire M. Fraser and colleagues at the US Centers for Disease Control and Prevention identified a recombinant between Ba and Bc when two hospital patients in Texas died of severe pneumonia. It appeared to have been caused by inhaling anthrax, but neither patient was infected with Ba. Instead, DNA tests showed that both patients were infected by a strain of Bc that normally causes mild food poisoning, but had somehow acquired lethal anthrax genes. What sort of disease agent might emerge from Bc if it acquired genes either from natural Bt or from GM Bt crop debris in the soil? GM Bt genes are significantly different from natural Bt and are completely untested for toxicity.

Dr Mae-Wan Ho and Prof Joe Cummins caution against growing GM Bt crops, especially in less industrially developed countries, where their use is increasing.