A Son of the Rock

As an SF reader and writer I was of course intrigued by the recent report in Science that a bacterium has been found that uses arsenic instead of phosphorus in its cell mechanisms. As a chemist, though, I was reasonably underwhelmed. While it is true that carbon, hydrogen, nitrogen, oxygen, sulphur and phosphorus are the six elements whose atoms are needed by most living things on Earth – trace quantities of other elements’ atoms are of course necessary for the full range of operation, iron in the haemoglobin of red blood cells for example – it wasn’t beyond the bounds of possibility that a particular organism would be able to substitute atoms of a similar element for one or other of these for certain purposes; especially if that organism lived in an extreme environment. Arsenic for phosphorus is not such a big jump. They are both in the same group of the Periodic Table, one directly above the other, and while arsenic is usually poisonous, cells working in an arsenic rich environment might be thought to be able to develop tolerance. It’s only a step from that to actually utilising the stuff. The reseachers seem to have given the organism concerned little choice in the matter, as the BBC report makes clear.

In all other respects it seems the biology of the bacterium is entirely on a par with the rest of life on Earth, some of which can live in all sorts of weird places.

So not alien, then, despite some of the hype. See Wired.

What would be really interesting would be if someone found a non-carbon based organism.

Don’t hold your breath.

Apart from anything else I don’t know if anyone’s looking – or what to look for if they did.