Nearly 400 Types of Bacteria Living in Human Intestines

I've read that our intestines contain several pounds of bacteria, responsible for digestion, vitamin metabolism, and immune functions. Now -- if you'll pardon a pun -- colonoscopies are shedding more light on the mysterious workings of gut bacteria.

A Stanford University study headed by Paul Eckburg, seeking to find links between intestinal bacteria and bowel diseases like Crohn's and ulcerative colitis, has identified 395 different species present in the colons of three Canadian subjects. About 80 percent had never been raised in the lab before.

There are more than 300 samples remaining to be analyzed, so the bacteria census is likely to grow in number and understanding.