Researchers Discover a Clever Strategy That Allows Enteric Pathogens to Survive in Anaerobic Environments

Researchers have discovered that certain pathogens manipulate the environment of the gut in order to boost their own growth. Enteric bacteria cause damage to encourage the proliferation of new cells, providing the pathogens with a consistent source of oxygen. The details are in a paper that was just published in the journal Science.

The gut contains beneficial microbes that play roles in metabolism, vitamin synthesis, and defense. These bacteria and other microorganisms are well-adapted to life in the digestive system. Most of the organisms found in the gut are anaerobic, requiring little or no oxygen to survive. Common enteric pathogens, including Escherichia coli, need oxygen yet are capable of outcompeting the digestive system microbiota.

To investigate how common enteric pathogens manage to thrive in a low oxygen environment, a team of researchers studied Citrobacter rodentium bacteria. C.rodentium infects mice and is comparable to pathogenic E.coli in humans; both invade the gut but need oxygen to survive. The team hoped to gain insight into how C.rodentium bacteria manage to compete with the natural microbiota present in the digestive system.

The research team found that the bacteria were using a type III secretion system to inject virulence factors into the intestinal lining. The body, in an effort to repair the damage, would begin to generate more epithelial cells. The new cells contained more oxygen, increasing overall oxygen levels in the gut. This allowed C.rodentium to thrive and easily compete with the anaerobic microbes already present in the digestive system.

The findings show that enteric bacteria strategically cause damage to force the production of new cells. These cells contain oxygen, allowing gut pathogens to survive and compete with beneficial microbes. The team used C.rodentium in mice as a model but the results can be applied to other enteric bacteria, including E.coli in humans. The authors believe that their research will lead to the development of treatments for dangerous antibiotic-resistant bacteria.  One such strategy would be to limit the bacteria’s ability to produce damaging virulence factors. Another possible treatment would involve giving the resident microbiota a boost. Treatment strategies that don’t rely on antibiotics are becoming more important as bacteria begin to resist common medications.

REFERENCE

A. Lopez et al. Virulence factors enhance Citrobacter rodentium expansion through aerobic respiration. Science (2016).

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