( For the first time scientists have def...)Gut reaction: Researchers define the colon's genome

In a study published in the June 2 issue of Science, scientists at The Institute for Genomic Research (TIGR) and their colleagues describe and analyze the colon microbiome, which includes more than 60,000 genes--twice as many as found in the human genome. Some of these microbial genes code for enzymes that humans need to digest food, suggesting that bacteria in the colon co-evolved with their human host, to mutual benefit.

"The GI tract has the most abundant, diverse population of bacteria in the human body," remarks lead author Steven Gill, a molecular biologist formerly at TIGR and now at the State University of New York in Buffalo. "We're entirely dependent on this microbial population for our well-being. A shift within this population, often leading to the absence or presence of beneficial microbes, can trigger defects in metabolism and development of diseases such as inflammatory bowel disease."

As in studies of other animals, the scientists began by collecting droppings. They collected fecal samples from two anonymous, healthy adults who'd gone without antibiotics or other medications for a year prior to the study. The researchers created DNA libraries based on the samples, generating a total of 65,059 and 74,462 sequence reads, respectively, from the two subjects. They found evidence for several hundred bacterial phylotypes, most falling into two divisions of bacteria known as Firmicutes and Actinobacteria. In addition, a microbial organism known as a methanogenic archaeon, Methanobrevibacter smithii, was prominent.

To assess the diversity of the colon microbiome, the researchers used two strategies. First, they matched their gut mi
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Source:The Institute for Genomic Research