Researchers at the Biotechnology Centre at the University of Oslo, led by Anne-Brit Kolstø, have determined that what were thought to be three separate bacterial species are actually three strains of the same species (Appl. Environ. Microbiol. 66, 2627–2630, 2000). This team had previously found evidence that Bacillus thuringiensis, the sire of Bt toxin, and B. cereus, a common cause of food poisoning found ubiquitously in the soil, appear to be the same species, exhibiting low degrees of clonality and frequent exchange of genetic material. Through multilocus enzyme electrophoresis (MEE) and sequence analysis of nine chromosomal genes, the Kolstø group now has found that B. anthracis, the cause of anthrax, belongs to the same species as well. The difference in phenotype is due to virulent plasmids harbored within B. anthracis. With B. anthracis currently undergoing complete sequencing, Kolstø plans to sequence genes in the closest B. cereus relatives to determine what exactly allows B. anthracis to retrieve and retain virulent plasmids. Although researchers should not be overly concerned by these findings, she says, they could have implications for “organic” pest control methods: “We do not know whether it would be dangerous to use B. thuringiensis as a whole bacterium for pesticidal reasons due to possible genetic transfer,” warns Kolstø.