Last update:
15-Jul-2013

The study of the human commensal micro-flora has recently regained the interest of the scientific community, particularly after the development of genomics and bio-informatics. The genes of the microbes found in the various different cavities of the human organism are collectively called the human microbiome (HM). This is a complex system, which is estimated to consist of approximately 1014 bacterial cells, thus being 10 times larger than the total of human cells. Almost 400−500 different types of microbes form the intestinal flora of the HM. The commensal bacteria in the gut microbiota interact with each other and with the host immune system, contributing to the homeostasis of the organism. The intestinal microbiome has been shown to differ among individuals of the same sex, between sexes and between individuals of different ages. Εach individual human can be characterized by his/her own intestinal microbial fingerprint, which may be useful in the future for individualized medicine. Alteration in the composition and function of the commensal gut microbiota has been associated with complex diseases such as inflammatory bowel diseases (IBD), colorectal cancer, allergies and obesity. Manipulation of the gut microbiota by fecal microbiota transplantation is an effective and safe treatment of IBD and infection with C. difficile, but the use of pre- and pro-biotics for the manipulation of microbiota should be reconsidered in the light of the new information now available. This is a review of recent findings concerning the role of the enteric HM in the development of the immune system, and its connection to gut-related and non-gastroenterological diseases.

Key words: Gut microbiota, Human microbiome, Metagenomics.