UO study looks at the gut’s defense against bad bacteria

University of Oregon researchers are helping to uncover the mechanisms at work when one ingests contaminated food or water.
EUGENE, Ore. — With the holidays over and all the rich and fatty foods behind us, if your gut still is feeling a bit off, it could be bad bacteria.
Bad bacteria from a questionable meal or contaminated water can “send your digestive tract into overdrive,” according to University of Oregon researchers who studied the mechanisms that drive our digestive track.
The good news is that with spasms and contractions, the intestines will expel everything in the gut, including bad bacteria — but the damage may already be done.
“When there’s damage, (the gut) has this fail-safe measure of just flushing the contents of the gut out by having these much stronger contractions,” said Karen Guillemin, a microbiologist and professor from the University of Oregon and collaborator on the study.
The new UO study showed that one kind of bacteria, Vibrio cholerae, triggers painful contractions by activating the immune system.
The research also found a more general explanation for how the gut rids itself of unwanted intruders, which could help scientists better understand chronic conditions, including inflammatory bowel disease.
“This isn’t a specific nefarious activity of the Vibrio bacteria,” stated Guillemin. “The gut is a system where the default is, when there’s damage, you flush.”
Vibrio cholerae is best known for causing cholera, which is typically associated with contaminated water. According to researchers, cholera infects millions of people per year.
In past work, study collaborator and physics professor Raghu Parthasarathy and his team demonstrated that Vibrio cholerae bacteria increased the strength of gut contractions in zebrafish.
The fish are transparent, so scientists observed what happened during digestion in real time.
“These days, we think of a lot of fancy molecular tools, but there’s still a great amount one can learn by taking a system and just carefully watching it,” he said.
The key player in the new research is a type of immune cell called a macrophage, which is known to calm neurons in the gut. When bacteria cause tissue damage, the macrophages tend to flock to the site of the problem, leaving their normal posts.
“Certain bacteria can poke at the gut and cause damage of different sorts,” said Parthasarathy, “and cause immune cells to move from one place to another.”
Guillemin said this relocation of immune cells sends the neurons into overdrive and triggers strong contractions. The researchers found enhanced gut contractions are beneficial for the host, whether zebrafish or human, since gut flushing is a swift way to remove bad bacteria.
The study also highlighted how the immune and nervous systems work together in gut health and how “cross talk” between systems might offer scientists insights into certain puzzling diseases.
They say the research offered a more general explanation of how our guts get rid of unwanted intruders, which could help scientists understand certain conditions like inflammatory bowel disease.
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