Recent research has generated intense interest in the bacterial ecology of the human digestive tract. The ability to analyze the collected DNA of gut denizens has allowed scientists to recognize how complex this microbiome can be.
In most cases, complexity is a good thing; various beneficial or at least neutral microbes can keep the more harmful ones from wreaking havoc. When the gut flora get wiped out, for example by antibiotics, less salutary species such as Clostridium difficile can take over and make life miserable. Some people have found that the best way to fight off such an infection is by re-introducing normal microbes through fecal transplantation.
Changes in the microbiome have been liked to a range of health conditions, including autoimmune diseases, allergy and even obesity. Inflammatory bowel disease seems to be associated with reduced diversity in the bacteria of the gut.
Now scientists have found evidence that viruses also play a role. A study of patients with Crohn’s disease and ulcerative colitis turned up DNA from previously unknown viruses that will warrant more research. Because some of these viruses are bacteriophages that attack bacteria, they might be responsible for the decreased diversity of bacteria in the colon in these conditions. It is unknown at this point how such viruses might colonize the digestive tract or how they could possibly be brought under control.