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[Michaelangelica]

maikeru did you watch the video? The guy was basically fired because he wanted to reseach soil bacteria-- in Australia's premier science organisation.

Plants are not the only life forms that depend on bacteria for food!

We are more microbe than man

It is said 'you are what you eat'. But Dr Karl says that when you eat you are feeding more than your appetite.

By Karl S. Kruszelnicki
Examining an x-ray scan

(Source: iStockphoto)
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* Audio: We are more microbe than man (ABC Science)

When you look at yourself in the mirror, it would be perfectly reasonable for you to assume that what you are looking at is mostly you.

Sure, there might be some bacteria living on your skin, maybe a flea that might have jumped off a passing dog, perhaps even some lice from a friendly neighbourhood preschool lice plague, but by and large, you should be mostly you.

But it turns out that hardly any of you is actually you.

Surprisingly, a lot of the science in this story comes from nursery rhymes.

You probably remember the one in which little girls are described as being made of "sugar and spice and all things nice". This is totally correct, because they are indeed made of sugars, fats and proteins.

But, would you believe it, another line from the same rhyme is also kind of correct when it says that little boys are made of "slugs and snails and puppy dogs' tails".

Yep, it's true. We humans are mostly made from other life forms.

So here's the really weird part.

Only about 10 per cent of the cells in your body actually belong to you. These add up to about 1–10 trillion cells.

The other 90 per cent of the cells in your body belong to other living creatures. The vast majority of these other living creatures are the 10–100 trillion single-celled beasties (such as bacteria) living in your gut.

In total, these bacteria and their little friends weigh about 1.5kg. The reason that they weigh so little, even though there are so many of them, is that these cells are much smaller than human cells.

The result is that each of us is a strange bacterial-human hybrid. On a cellular level, we are more microbe than man.

The bacteria started colonising your gut as you came down the birth canal, and were pretty well established by the time you were two years old.

Your gut is surprisingly large. If you rolled it out it would be as long as a bus, and if you flattened it out, it has the surface area of a football field.

There are at least 1000 different species of these single-celled critters colonising your gut.

It's quite a fair and reasonable relationship that we have with them.

On one hand, they do their own thing, in the comfort and safety of the human gut. They make little baby copies of themselves, and they communicate with each other.

And when we eat, they eat. They store and redistribute energy, and they maintain and repair themselves.

We are more microbe than man › Dr Karl's Great Moments In Science (ABC Science)