10% human and 90% bacterial

You'd be nothing without the trillions of microbial minions toiling in your large intestine, performing crucial physiological functions that your highfalutin human cells wouldn't have a clue how to do.

That's one of the humbling truths emerging from the most thorough census yet of the bacterial tenants homesteading in our bodies. The new view, made possible by cutting-edge DNA screening methods, shows that the vaunted human genome -- all the genes in our cells -- is but a fraction of what it takes to make a human.

In fact, it's time to stop thinking of yourself as a single living thing at all, say the scientists behind the new work. Better to see yourself as a "super-organism," they say: a hybrid creature consisting of about 10 percent human cells and 90 percent bacterial cells.

...as it turns out, no small number of [the biological functions many of these microbes are performing] are crucial to human survival.