There are both good and bad bacteria in our bodies. The balance of the intestinal bacteria group is essential for health. Now, a new research from University of California Irvine has identified that the beneficial bacterium Escherichia coli Nissle 1917 (EcN) secretes small proteins called microcins that limit the growth of harmful gut bacteria during intestinal inflammation. Described in the prestigious journal Nature, the work may help treat inflammatory bowel disease (IBD).
In a healthy intestine, Enterobacteriaceae only accounts for a small percentage of the gut microbiota. But in the inflamed gut, some strains of the bacteria can bloom. In fact, overpopulation of enterobacteria is a sign of intestinal flora imbalance. Scientists have known for a while that microcins possess antimicrobial activity in vitro. However, their effect in vivo remains elusive till the present moment.
To better understand the role of microcins, senior researcher Manuela Raffatellu and colleagues conducted this research. They induced bowel inflammation in mice, and investigated the effect of microcin-producing EcN on the bacterial populations in the gut, especially the bacteria that become unbalanced in IBD.
Results showed that with the help of microcins, the probiotic bacterium EcN was able to inhibit the growth of competitors in an inflamed gut, including some pathogenic strains of E. coli and Salmonella species. When Salmonella-infected mice were given the wild-type, microcin-producing EcN, the researchers found a significant decrease in the amount of Salmonella in the mice's gut. Together, microcins help EcN to compete with harmful bacteria in the gut.
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