GI Microbiota and Regulation of the Immune System

The idea that the microbial communities within the GI tract have a profound influence on general human health actually originated with Russian scientist Elie Metchnikov at the turn of the last century. Also known as the "father of immunology", Metchnikov believed that putrefactive bacteria in the gut were responsible for enhancing the aging process. He theorized that ingestion of healthy bacteria found in fermented foods could counteract toxic bacteria and was the key to good health. His theories concerning good bacteria and health can be found in his treatise "The Prolongation of Life: Optimistic Studies". These writings prompted Japanese scientist Minoru Shirota to begin investigation of how fermentative bacteria improve health. He succeeded in isolating a strain of Lactobacillus that could survive passage through the intestine, while promoting a healthy balance of microbes. The "Shirota strain" is still used today in the fermented beverage Yakult. It is clear from a commercial standpoint that these ideas have inspired the development of a probiotic industry, which has expanded greatly in the U.S. over the past 5-10 years. Likewise, scientific studies investigating the microbiota and the immune system have increased significantly in recent years. This increase in research is also due to advances in technologies that enable the investigation of large microbial communities, a resurgence in gnotobiotic animal research, and improved methods for molecular analysis of probiotic bacterial species. Our interest in this area stems from our laboratory observations indicating that antibiotics and fungi can skew microbiota composition and systemic immune responses. Our initial base of references upon which to develop further hypotheses concerning the mechanisms involved in microbiota regulation of immune responses was limited. However, in presenting the research at national scientific meetings and at universities across the country, the feedb