published in life
In the human body, 500 to 1000 different species of microorganisms can be found. Among these, 99% are strict anaerobes (i.e. they survive in absence of oxygen). The intestinal bacterium that is best known in man is Escherichia coli. Intestinal flora develops during the course of the first days of life and survives, except in case of diseases, for a surprisingly long time . In an adult man, the intestinal flora consist of approximately 1014 cells (i.e. 100,000 billion bacteria, a number that is more or less analogous to that of human cells in the body) for a total weight of 1.5 kg.