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"The significance of the microbial community has been overlooked," Broderick asserts. "Ultimately, this is a toxin-mediated septicemia (blood poisoning) modulated by the gut community."

The exact role played by the microbes to promote the Bt toxin's lethal effects remains unknown.

The upshot of the new work may have immediate application in designing strategies to manage insect pests by enhancing the killing effects of BT using indigenous insect gut microbes or other bacteria known to promote blood poisoning.

"The work also raises the possibility that the genes encoding the (Bt) toxins could be deployed more effectively in transgenic crops by exploiting the role of insect-borne bacteria that enhance insecticidal activity," the Wisconsin team writes in its PNAS report.

What's more, the insight that gut microbes mediate the effects of bacterial toxins could have application in human and animal medicine as the roles of those bacteria become better understood. Bacterial infections in humans may account for as much as 10 percent of mortality in the United States.

"It is thought that the gut is the source of bacteria for a large portion of cases of human septicemia, so if this mechanism is shared by Bt and toxins produced by human pathogens, the implications could be far greater in medicine than in agriculture," Handelsman says.
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Source:University of Wisconsin-Madison