h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

What I mean is, is this bacterium a fluke? Or is it one of a group that are deliberately adapted to be able to survive for milions of years?

Because, if it was, then they could survive almost anything, for example all the stuff that was going on when the Solar System was young - which could mean that life is older than we thought.

They could also - I think this is a little unlikely - travel through space.

I think the scientists believe similar things could travel through space on cometary material.

I don't think a bacteria can be said to adapt in an evolutionary sense to such an unusual occurance. There would be no significant selection pressure from such rare events.

That is not so say that the features which allow it to survive for so long are not adaptations - but they would be selected for other reasons (surviving a hot summer on a dessicated lake bed, for instance) - long term survival wasn't what was being aimed at.

Of course, having fortuitously inherited adaptations which incidentally allow it to survive in space, or 'death' for 250 million years, then it *could* be transported by comet perhaps.

Cheers

Konrad

For the individual there is unlikley to be an evolutionary pressure towards superlongevity - but for the survival of a species it would be very useful. Thus with periodic catastrophic events all those bacteria which can't go in to suspended animation will be killed off - leaving only those that can to exploit the post event planet.

Indeed, it would be beneficial, but not an adaptation. The word implies selection; a fortuitous mutation is just that - a fortuitous mutation, not an adaptation.

It could only be an adaptation to superlongevity if evolved *in order* to exploit catastrophic events by long term suspended animation. It could not be an adaptation to cometary transportation or eons in desicated beds because the possibility of this happening to the species more than once is infinitesimal - and if only one generation has been exposed to that selection pressure it isn't evolution.

The most likely explanation is an adaptation to periodic desication over frequent dry summers, which incidentally allows superlongevity.

Konrad

What I still don't understand is why the bacterium didn't suffer damage at the atomic level - through radiation, cosmic rays etc. The effects in any given year are tiny - but over a period of 250 million years I would expect them to have made the bacterium non viable.
Did/does the bacterium have some sort of repair mechanism? If so - where did that derive its energy?

There are probably three factors at work.

Firstly, most penetrating non-ionising radiation does virtually no damage to a cell, so provided the cell is kept away from alpha and beta sources the chance of damage would be small.

Secondly, there is probably a quantity of DNA that does not usefully code for anything in bacteria, as there is for mamals. Damage that and it won't have an effect.

Thirdly, I'm not sure how many cells were found, it could be that the ones which had been damaged were unviable, but there was a big enough population to save some of them.

Just speculating here, mind you.

Konrad

Apparently it is quite similar to other modern bacilli in the Dead Sea. Makes sense really, given the salt factor.