A standard character in science fiction is the foe that continually changes shape, so that a protagonist's victories are always temporary. To biomedical researchers studying human pathogens, this scenario is depressingly familiar.

Escherichia coli bacteria are generally harmless, but can
become dangerous by acquiring new bits of
DNA from other
organisms.

"Bacteria are constantly changing," says B. Brett Finlay, an HHMI international research scholar at the University of British Columbia, who studies pathogenic strains of the common intestinal microbes Escherichia coli and Salmonella. "And when they find something that works, they hang onto it—at least until their enemies develop new weapons and the bacteria need to change again." continued...

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Reprinted from the HHMI Bulletin,
March 2002, pages 26-29.
©2002 Howard Hughes Medical Institute