The toxin, produced by different types of bacteria in different hosts, is known as tracheal cytotoxin. And the astonishing discovery that it can be either good or bad - depending on its biological context - promises to rattle long-held perceptions of microbes and their role as pathogens.

The new work, funded by the National Institutes of Health, was reported this week (Nov. 12) in the journal Science.

That the same toxic molecule produced by different bacteria in different host animals plays such disparate roles - disease and massive tissue damage on the one hand, and critical organ development on the other - may force biologists to rethink the relationship between the world's many microorganisms and their host plants and animals, according to Margaret McFall-Ngai, a University of Wisconsin-Madison professor of medical microbiology and the corresponding author of the Science paper.

"It is all context dependent," says McFall-Ngai. "It has to be that we have mechanisms to use these molecules in different ways. Until now, molecules of a virulent nature have not been recognized as having essential roles in development."

In the diminutive Hawaiian bobtail squid, the toxin was found to spur the development of a structure, a light-producing organ that acts as a sort of "Klingon cloaking device," mimicking starlight to confuse hungry predators lurking in the depths. In humans, the same toxic molecule, produced by different species of bacteria, causes massive tissue damage in the lungs in the case of whooping cough, and in the fallopian tubes in the case of gonorrhea.

When the squid are born, they are about half the size of a grain of rice, and they must acquire the toxin-producing bacteria from their oc
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Contact: Margaret McFall-Ngai
mjmcfallngai@wisc.edu
608-262-2393
University of Wisconsin-Madison
11-Nov-2004