Killer ‘Smart Bacteria’ Found to Wreak Havoc on the Gut


Scientists have unlocked some mysteries about a deadly diarrhea that kills more than two million babies each year in developing nations.

In what is described as a “touchdown for gut pathogen virulence” in the prestigious academic journal Science, professor Ilan Rosenshine and colleagues from The Hebrew University of Jerusalem have determined how E. coli wreaks havoc in the intestines after finding their way there via contaminated food.

The researchers figured out that the bacteria can somehow sense they have become attached to intestinal cells inside a human and begin to express their genes.

Credit: Ryan Kitko/Flickr, CC BY 2.0

The scientists made their discovery by engineering one of the genes to express a protein that would stain expressing bacteria green. “Under microscopic examination, the researchers observed that only the attached bacteria fluoresce in bright green, whereas non-attached bacteria remain dark,” The Hebrew University of Jerusalem explained in a news release.

“The researchers also deciphered how upon sensing that it has attached to intestinal cells, the pathogen reorganizes its gene expression, including genes involved in virulence and metabolism, to exploit the host cell. These findings may lead to development of new strategies to combat bacterial infection.”

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Calling the pathogens that cause the killer diarrhea “smart bacteria,” the researchers explained that they essentially “remodel” their genes to upset the balance in the gut. “Enteropathogenic E. coli (EPEC) first sticks to the host by means of pili,” Science explains. Pili are like hairs on bacterium. The bacteria then inject damaging “effectors” into the host cell.  But not all the disruptors delivered to the cells are injected directly. Others come to the cell via “bacterial chaperones” known as CesT first.

“Then, with the bacterial cytoplasm, it interacts with a gene repressor called CsrA, which reprograms bacterial gene expression to help the bacteria to adapt to epithelial (intestinal) cell-associated life,” Science editors explain.

While it sounds highly technical, this knowledge may lead to cures and prevention of this widespread diarrhea that kills so many without warning.

Earlier this month, Rosenshine and colleagues made another significant discovery about deadly bacteria. That paper was published in the journal eLife.

This petri dish holds E. coli bacteria. Credit: VeeDunn/Flickr, CC BY 2.0

“Ronin et al. show that cells in enteropathogenic E. coli spontaneously form into two groups when exposed to conditions that mimic the environment inside the human body,” eLife explains in an editor’s summary. “Once triggered, one of these groups is particularly dangerous and this ‘hypervirulent’ state is remembered for an extremely long time meaning that the bacteria remain hypervirulent for many generations.”

In addition, Ronin et al. identified the specific genes that control the switch to the hypervirulent state.

“These findings have uncovered the existence of groups of enteropathogenic E. coli that are pre-adapted to invading human hosts. Finding out more about how the switching mechanism works and its relevance in other bacteria may help researchers to develop new therapies that can help fight bacterial infections.”

Related: Balancing Gut Bacteria Could Be the Key to Solving Chronic Stomach Problems