A Short History of Nearly Everything (Bryson) by Bill Bryson

Author:Bill Bryson [Bryson, Bill]
Language: eng
Format: azw3
ISBN: 9781409095484
Publisher: Transworld
Published: 2010-01-23T05:00:00+00:00

20

SMALL WORLD

It’s probably not a good idea to take too personal an interest in your microbes. Louis Pasteur, the great French chemist and bacteriologist, became so preoccupied with his that he took to peering critically at every dish placed before him with a magnifying glass1, a habit that presumably did not win him many repeat invitations to dinner.

In fact, there is no point in trying to hide from your bacteria, for they are on and around you always, in numbers you can’t conceive of. If you are in good health and averagely diligent about hygiene, you will have a herd of about one trillion bacteria grazing on your fleshy plains2 – about a hundred thousand of them on every square centimetre of skin. They are there to dine off the ten billion or so flakes of skin you shed every day, plus all the tasty oils and fortifying minerals that seep out from every pore and fissure. You are for them the ultimate buffet, with the convenience of warmth and constant mobility thrown in. By way of thanks, they give you B.O.

And those are just the bacteria that inhabit your skin. There are trillions more tucked away in your gut and nasal passages, clinging to your hair and eyelashes, swimming over the surface of your eyes, drilling through the enamel of your teeth. Your digestive system alone is host to more than a hundred trillion microbes, of at least four hundred types3. Some deal with sugars, some with starches, some attack other bacteria. A surprising number, like the ubiquitous intestinal spirochetes, have no detectable function at all4. They just seem to like to be with you. Every human body consists of about ten quadrillion cells, but is host to about a hundred quadrillion bacterial cells5. They are, in short, a big part of us. From the bacteria’s point of view, of course, we are a rather small part of them.

Because we humans are big and clever enough to produce and use antibiotics and disinfectants, it is easy to convince ourselves that we have banished bacteria to the fringes of existence. Don’t you believe it. Bacteria may not build cities or have interesting social lives, but they will be here when the Sun explodes. This is their planet, and we are on it only because they allow us to be.

Bacteria, never forget, got along for billions of years without us. We couldn’t survive a day without them6. They process our wastes and make them usable again; without their diligent munching nothing would rot. They purify our water and keep our soils productive. Bacteria synthesize vitamins in our gut, convert the things we eat into useful sugars and polysaccharides, and go to war on alien microbes that slip down our gullet.

We depend totally on bacteria to pluck nitrogen from the air and convert it into useful nucleotides and amino acids for us. It is a prodigious and gratifying feat. As Margulis and Sagan note, to do the same thing industrially (as when

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