Our digestive tract hosts more than 1014 micro-organisms divided into several hundreds of different bacteria, viruses and yeasts. If these bacteria have a weight of approximately 1Kg for an adult, they are ten times more numerous than the number of human cells and represent more than 95% of genes present in our organism. This intestinal flora is exclusive to each individual, is controlled by human genes, nutrition, age, ways of life and geographical place. One can thus consider each human as a superorganism able to host bacteria which enable him to increase the diversity of its genome of more than 100 times.
In order to properly characterize, on a molecular level, the bacteria of the intestinal flora and their functions, several American, European, Chinese, Canadian and Australian research organizations provided funds devoted to calls for proposals on the microbiome. Particularly, the purpose of the MetaHit European program, granted with 31 million USD, is to better understand the functions of bacteria present in the digestive flora and among others during chronic inflammatory bowel diseases. Complementarity of all these projects and the level of their grant should make it possible, in a near future, to better understand function of these micro-organisms, to analyze the criteria causing the bacteria colonization in our digestive tract, to seek the characteristics of the human microbiome, and the means of modulating it to extract the therapeutic properties.
(Mullard A. Nature 2008 ; 453 : 578-80)