Bugs are Us

Here are some fascinating snippets from an article by Carl Zimmer in his Discover magazine blog. I've bolded the key bits:

There are probably 100 trillion microbes inside each of us, such that our bodies are ten microbes for every one human cell. Those tenants probably belong to several thousand species, with a collection of genes that’s perhaps a 100 times bigger than the human genome. These microbes live in our guts, lungs, mouths, noses, skin, and many other nooks and crannies. Far from making us sick, they help us in many ways, making food for us, defending us from invaders, and nurturing our immune systems.

These bacteria are also hosts to viruses. In World War I, the Canadian doctor Felix d’Herelle discovered the first virus infecting bacteria while studying the stool of French soldiers sick with dysentery. Once he isolated the bacteria-attacking virus, he could use it to destroy cultures of the dysentery-causing bacteria. He dubbed them bacteriophages (eaters of bacteria). In the decades since his discovery, scientists have discovered a mind-boggling number of bacteriophages in the ground, the oceans, and even in deep caves. They are, in fact, the most abundant form of life on Earth. Now researchers are turning the tools for identifying bacteriophages back to our own body.

Last year, Jeffrey Gordon and his colleagues looked in the guts of four pairs of identical twins and their mothers and discovered over 4,000 different kinds of viruses among them. Each person had several hundred kinds apiece. Most of these viruses were not predators, like the viruses that attack dysentery-causing bacteria, or the ones the give us a cold. Instead, the viruses merge with their host cell. They can be passed down from one generation to the next; only if they sense danger do these viruses break out of their host.

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It’s astonishing for most people to learn there are between 500 and 1000 species of bacteria in their mouths. But now we must begin to get used to the fact that those bacteria are in a constant battle with hundreds–perhaps even thousands–of different viruses. One reason it’s such a big surprise is that these battles take place without any noticeable effect on ourselves. But it would be a mistake to think that they have no effect at all. The state of our mouth’s ecosystem plays a big role in our overall health.

Go read the whole thing to get all the dirty little details!