One for All and All for One

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Science  16 Jun 2000:
Vol. 288, Issue 5473, pp. 1933
DOI: 10.1126/science.288.5473.1933c

Remarkably, it appears that the ubiquitous soil-living bacterium and occasional food-poisoning culprit Bacillus cereus, the widely used insect biocontrol pathogen Bacillus thuringiensis, and the life-threatening biological warfare agent Bacillus anthracis are the same species, despite the striking differences in phenotype. The secret appears to lie in the plasmids harboured by B. anthracis and B. thuringiensis.

When ten B. cereus-like strains were isolated for biochemical and genetic analysis from soil taken from anthrax outbreak sites, they were found by Helgason et al. to have the same chromosomal marker as the implicated B. anthracis strains, but no plasmids. In their natural environments these species have a relatively low rate of clone formation, and it is known that all three Bacillus species are naturally able to take up plasmids. Indeed, plasmid exchange between B. cereus and B. anthracis has been verified experimentally. However, before sounding a general alarm, it cannot be ruled out that there is some other special, but as yet undetected, feature of the B. anthracis genome that makes it alone of the three species particularly adept at retrieving and retaining virulence plasmids.—CA

Appl. Environ. Microbiol.66, 2627 (2000).

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