22 July 2009

The typical human is home to a vast array of microbes. If you were to count them, you’d find that microbial cells outnumber your own by a factor of 10. On a cell-by-cell basis, then, you are only 10 percent human. For the rest, you are microbial. (Why don’t you see this when you look in the mirror? Because most of the microbes are bacteria, and bacterial cells are generally much smaller than animal cells. They may make up 90 percent of the cells, but they’re not 90 percent of your bulk.)

This much has been known for a long time. Yet it’s only now, with the revolution in biotechnology, that we’re able to do detailed studies of which microbes are there, which genes they have, and what they’re doing. We’re just at the start, and there are far more questions than answers. But already, the results are astonishing, and the implications profound.

Even on your skin, the diversity of bacteria is prodigious. If you were to have your hands sampled, you’d probably find that each fingertip has a distinct set of residents; your palms probably also differ markedly from each other, each home to more than 150 species, but with fewer than 20 percent of the species the same. And if you’re a woman, odds are you’ll have more species than the man next to you. Why should this be? So far, no one knows.

via Microbes ‘R’ Us - Olivia Judson Blog - NYTimes.com.

An interesting article on the continuing discoveries of the inner life of the human body.  Of particular interest:

Moreover, whereas humans are extremely similar to one another at the level of the genome, the microbiome appears to differ markedly from one person to the next.


Diet has some effect: a diet rich in sugars and fats reduces the diversity of gut bacteria, and shifts the balance towards those that are more efficient at extracting energy. Start eating more plants and you can shift the balance back, and increase the diversity of your gut microbes.


First, during your lifetime, your bacteria can change their genes even though you cannot change yours….It may be that gut bacteria evolve in response to short-term changes in the environment, especially exposure to food-borne diseases. They may thus act as an evolving supplement to the immune system.

…Because bacteria can evolve so fast, it may be that some of what we think of as human evolution — like the ability to digest new diets that accompanied the invention of agriculture — is actually bacterial evolution.

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