About a hundred trillion bacteria are living in the pit of a human’s stomach. But that’s not necessarily a bad thing.
With the help of some fish, University researchers found that the body tolerates the bacteria, and they found the bacteria help digest food in the gut.
The research marks another study using zebrafish at the University, which is recognized as the center for zebrafish research in the science community. Scientists say zebrafish could help find treatments for inherited diseases because the fish make for ideal experiment specimens.
University researcher Karen Guillemin found that a common enzyme, called intestinal alkaline phosphatase, in the intestines of all fish and humans plays a role in detoxifying a component of the cell wall of many bacteria that reside in the intestine as symbionts. University graduate student Jennifer Bates, undergraduate researcher Janie Akerlund and research assistant Erika Mittge helped Guillemin in the study.
“This finding helps answer a long-standing puzzle, which is why our bodies don’t undergo a massive inflammatory response to these symbiotic bacteria,” Guillemin said in an e-mail. She is currently at home with a newborn son.
The research also provides a better understanding of interactions with the bacterial symbionts in the gut. These interactions are thought to at least partly cause some diseases, including some inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis.
“Our studies demonstrate one way in which the body deals with the potential inflammatory nature of these bacteria by detoxifying the bacterial molecule that normally stimulates the inflammatory response,” Guillemin said.

This same method could be used to prevent or treat intestinal inflammation in the case of certain inflammatory bowel diseases, Guillemin said.
The research was published in the journal Cell Host & Microbe and Science magazine.
Although Guillemin’s work veers slightly from the University’s approach of using zebrafish in genomics studies, Guillemin said zebrafish were used because they’re similar to humans in the development and physiology of their digestive and immune systems.
Bill Trevarrow, the former director of the University Zebrafish Facility, describes zebrafish as an “aquarium shop fish with horizontal stripes,” and he said they’re easy to breed and care for.
“That alone makes them well-suited for labs,” Trevarrow said.
The zebrafish’s eggs develop outside the mother’s body, and scientists can watch an egg grow under a microscope because the embryo is clear, Trevarrow said.
“You can see what all of the cells are doing in the first few days of development,” he said.
The zebrafish is ideal for studying vertebrate development, biology professor Monte Westerfield said. “The only other major vertebrae organism for studying genetics is the mouse, and to some extent the rat,” Westerfield said. “Compared to mice, fish are much cheaper and easier to maintain in a laboratory setting. They develop rapidly.”
The University is regarded as a pioneer in zebrafish research. Millions of zebrafish researchers across the world still look to the University for information and use the University’s online zebrafish database systems.
Zebrafish research began with the late George Streisinger more than 30 years ago, Westerfield said, adding Streisinger wanted to apply the studies of genetics to vertebrates.
Streisinger’s research has been carried on by the likes of Westerfield, biology professor Charles Kimmel and biology professor Judith Eisen. The University has also showed strong support in zebrafish research – President Dave Frohnmayer even devoted an entire convocation speech to the topic in 2003.
Today, about 5,000 researchers in 450 labs throughout 31 countries study zebrafish, Westerfield said.
Many of those labs are staffed with researchers who studied at the University.
Westerfield said he’s excited about the study of zebrafish because the field is working its way toward treating human diseases. Researchers are able to mutate genes in a fish to mimic a disease, study the response and figure out how to treat it.
Zebrafish could be used to treat genetic diseases in humans, Westerfield said.
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