It was thought until very recently that the human intestinal tract harbored anywhere from 400 to 500 different species of mostly friendly bacteria. These bacteria play a very important role in maintaining our health. They function as a first line of defense against potentially invasive pathogenic bacteria, an immune system response. There are 10 times more bacteria in the digestive system than there are cells in the human body. These good guys also play a vital role in digestion and the manufacture of certain bacteria such as vitamin b12. We as a species have co-evolved with thes micro-organisms over thousands if not millions of years. We need them, they need us, plain and simple. Now the latest Science indicates that our inner ecosystem is even more complex than was ever imagined. Through the latest genetic dna sequencing it has been shown that the average person has anywhere from 3500 to 5700 different or distinct bacterial species or stains. "In sheer numbers, the mammalian colon harbors one of the densest microbial communities found on earth". To make an analogy, think of the human colon as rich and diverse as the amazonian rainforest.