Harnessing Commensals

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Science  16 Jul 2010:
Vol. 329, Issue 5989, pp. 258
DOI: 10.1126/science.329.5989.258-a

Our gastrointestinal tracts contain a variety of commensal bacteria that digest our food, kill harmful microorganisms, and help us function. Investigators are beginning to engineer such bacteria to make them even more beneficial. Duan and March have augmented a signaling pathway that enables a model probiotic bacterium, Escherichia coli Nissle 1917 (Nissle), to ward off cholera. The pathogenic bacterium Vibrio cholerae contains a signaling pathway that is sensitive to secreted autoinducers whose environmental concentration increases as the population density increases. At high cell densities, these autoinducers inhibit the expression of virulence genes (for cholera toxin and the intestinal attachment pilus). The authors transformed Nissle with a construct containing the gene cqsA, which is required for synthesis of the autoinducer. When infant mice were fed with transformed Nissle 8 hours before challenge with V. cholerae, 92% survived. Protection was less at shorter pretreatment times and at lower doses of transformed bacteria and was associated with a decrease in the numbers of V. cholerae in the intestines of infected mice. Although much further work needs to be done, the authors speculate that this might be an important preventive approach in regions where natural disaster increases the probability of an outbreak or even as part of the diet in impoverished areas.

Proc. Natl. Acad. Sci. U.S.A. 107, 11260 (2010).

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