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Tiny toxic proteins help gut bacteria defeat rivals

Microcins attack pathogens involved in gut inflammation

10:00am, November 28, 2016

GERM WARFARE  When iron gets scarce, a bacterium called E. coli Nissle deploys molecules called microsins that kill some other types of bacteria, including other strains of E. coli.

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Bacterial proteins that kill rival bacteria

Competition is cutthroat in the crowded world of the intestines, so bacteria have evolved ways to kill rivals for a survival advantage. One strain of bacteria, called Escherichia coli Nissle 1917, has tiny proteins called microcins that may help E. coli’s host fight pathogens that cause gut inflammation, researchers at the University of California, Irvine report online October 31 in Nature.

Microcins take action only when bacteria are starved for iron, which happens in an inflamed gut. The proteins go after bacteria, many of them pathogens, that make iron-scavenging proteins, the researchers found. E. coli Nissle’s microcins killed diarrhea-inducing bacteria called Salmonella enterica in the guts of infected mice. Microcins also helped Nissle outcompete a different, nasty strain of E. coli.


M. Sassone-Corsi et al. Microcins mediate competition among Enterobacteriaceae in the inflamed gut. Nature. Published online October 31, 2016. doi:10.1038/nature20557.

Further Reading

T.H. Saey. How one scientist’s gut microbes changed over a year.Science News. Vol. 190, October 1, 2016, p. 32.

E. Landhuis. Genes that control toxin production in C. difficile ID’d. Science News Online. August 16, 2016.

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