Credit: David M. Phillips/Photo Researchers, Inc.

There's more than bacteria to the intestinal flora. According to a report in Science (336, 1314–1317), the gut contains indigenous fungi that interact with the immune system and may influence the course of bowel disease.

Previous studies had hinted at the existence of fungi in the gut flora. Following that lead, Iliyan Iliev et al. looked for fungal genetic material in the gut of mice and found evidence for the existence of over 100 different species.

As many fungal species interact with the innate immune receptor dectin-1, the team went on to study mice lacking this receptor to see whether they were differentially susceptible to inflammatory disease. In a model of chemically induced colitis, mice deficient for dectin-1 had worse disease, probably owing to an inability to keep the indigenous fungi in check.

These observations may be also relevant to humans, as the researchers identified a polymorphism in the gene for dectin-1 that is associated with a severe form of ulcerative colitis.