gut Bacteria’s role in Ulcerative Colitis Unveiled: A Bacterial Toxin Disrupts Immune Defense
Ulcerative colitis (UC) is one of the most common inflammatory bowel diseases, a lifelong condition that can cause chronic inflammation and ulcers in the lining of the large intestine. This can lead to symptoms such as rectal pain and bleeding, and persistent diarrhea. It is indeed thought to be an autoimmune disease, but exactly what triggers it remains unclear.
However, a team of researchers led by Fangyu Wang, Xuena Zhang, and Minsheng Zhu at Nanjing University has discovered a bacterial toxin that destroys key immune cells that protect the gut, which may explain how the disease takes hold. The study is published in the journal science.
Previous research has shown that macrophages, a type of immune cell that helps eliminate foreign substances (like pathogens and debris), are crucial for protecting the gut barrier and preventing inflammation. The team’s analysis of tissue samples revealed that these defenders were largely absent from the protective layer just beneath the colon’s surface in UC patients.
Identifying the culprit
To test their theory that something must be actively destroying gut macrophages, the scientists frist studied fecal s
Gut Bacteria Linked to Ulcerative Colitis
New research suggests a specific type of bacteria, Aeromonas, might play a key role in causing ulcerative colitis. Scientists have discovered a version of this bacteria that produces a toxin called aerolysin. This toxin seems to weaken the gut’s natural defenses, making it easier for the disease to develop.
Ulcerative colitis is a chronic inflammatory bowel disease that causes inflammation and ulcers in the large intestine. Symptoms can include abdominal pain, bloody stool, and urgent bowel movements. Currently,treatments focus on managing symptoms,but a cure remains elusive.
The study, published in the journal Science, found that aerolysin disables a protective layer in the gut. This layer normally prevents harmful bacteria from damaging the intestinal lining. When this layer is compromised, inflammation can occur, perhaps leading to ulcerative colitis.
Researchers tested this by introducing the aerolysin-producing Aeromonas to mice. The mice became more susceptible to developing colitis. They also found higher levels of this bacteria in the guts of people with ulcerative colitis compared to healthy individuals.
“This finding opens up new avenues for potential treatments,” says Zhihui jiang, a lead author of the study. “If we can find ways to block the effects of aerolysin or reduce the amount of this bacteria in the gut, we might be able to prevent or treat ulcerative colitis.”
Further research is needed to fully understand the connection between Aeromonas, aerolysin, and ulcerative colitis. Though, these findings offer a promising new target for developing more effective therapies.
More information: Zhihui Jiang et al,An Aeromonas variant that produces aerolysin promotes susceptibility to ulcerative colitis,Science (2025). DOI: 10.1126/science.adz4712
Sonia Modilevsky et al, A bacterial toxin disarms gut defenses against inflammation, Science (2025).DOI: 10.1126/science.adh3448