Microbes and colorectal cancer: is there a relationship?

The human colon plays host to as many as 15,000–36,000 bacterial species, amounting to more than 100 trillion bacteria 1,2. The microbiota and their associated prokaryotic genome is an integral part of the host and uniquely contributes to various biologic processes such as maturation and development of the mucosal immune system, metabolic capacity, and intestinal epithelial cell proliferation and differentiation 3. An international effort is currently underway to catalogue the repertoire of microorganisms present in the intestines of healthy humans and of those with pathologic conditions. The human microbiome project—for which the U.S. National Institutes of Health has contributed more than $110 million—is aiming to determine the structure of the microbial community associated with the human body and the functions thereby served in health and disease 3,4