Each person shelters about 100 trillion microbes

Interesting NY Times article:http://www.nytimes.com/2011/04/21/science/21gut.html In the early 1900s, scientists discovered that each person belonged to one of four blood types. Now they have discovered a new way to classify humanity: by bacteria. 

It turns out that we only have 10 trillion cells, but ten times as many microbes in us! If you find this sort of stuff interesting, here is some must viewing: Dr. Kiki's Science Hour 89: Bacteria, Viruses And Parasites,  This is "nerd" internet TV and the production quality is not indicative of the content,  The guest is an expert science writer. It starts slow, but ramps up ...  I posted this review:

This provocative video is important for all scientists and theologians and farmers alike. In ordinary language, it has implications for everyone. I won't explain the relevance to all disciplines but it is must viewing. The meat starts about 7-8 minutes in ... but the introductory humor "A virus walks into a bar ..." shouldn't be off-putting. I learned more and thought more from this relaxed production than I ever did from any slick piece of NOVA work. Kudos and 5 plus stars. Watch it!