[dentstudent (OP)]

This may have been covered before, but I heard on another pod (traiter!) that "life does not exist anywhere without water".

Is this really true?

[another_someone]

I think the only thing we can really say is that we have not found life without water.

A lot of it comes back to having a clear definition of what life is.

I think it reasonable to say that DNA/RNA could not function without water, and we have not yet extended the concept of 'life' to anything that does not have DNA or RNA as a core component.

[JimBob]

There are extremophiles that can live in and feed from rocks. They are call lithoautotroph, deriving their carbon from the breakdown of minerals such as pyrite in limestone. Some of these do not need water to survive. They can derive the hydrogen and oxygen from the rocks.

[another_someone]

There are extremophiles that can live in and feed from rocks. They are call lithoautotroph, deriving their carbon from the breakdown of minerals such as pyrite in limestone. Some of these do not need water to survive. They can derive the hydrogen and oxygen from the rocks.

Are you saying that these organisms do not need water at all, or only that they can synthesise sufficient water to meet their needs?

[JimBob]

There are extremophiles that can live in and feed from rocks. They are call lithoautotroph, deriving their carbon from the breakdown of minerals such as pyrite in limestone. Some of these do not need water to survive. They can derive the hydrogen and oxygen from the rocks.

Are you saying that these organisms do not need water at all, or only that they can synthesise sufficient water to meet their needs?

They synthesize their own. The important thing here is that although, yes, water is used in their metabolism, it is not necessary to have an outside source - they are unlike all other organism in this.

OK, I can hear it now, "But they use water."  I acknowledge that. I am merely bringing up this rather obtuse fact. That is all.

 

 

[dentstudent (OP)]

Perhaps I could clarify the question. "In the absence of water" might better suit. If the organisms can create their own, then that qualifies. I really want to know if there HAS to be water first, rather than as a metabolic by-product.

George, you were saying that DNA needs water? Please can you explain this, and whether the lithoautotrophs described by JimBob therefore need water in the first instance.

Wasn't there was a short piece recently on TNS about organisms that fed on radioactivity?

[paul.fr]

Wasn't there was a short piece recently on TNS about organisms that fed on radioactivity?

There was, Stuart.

i am way too tired to think too straight, but i think they lived in or around Chernobyl. i seem to remember another one that lived deep in the ocean that fed of heat or something from volcanoes!

that last one could be wrong, but i think i am right with the first.

[paul.fr]

http://www.thenakedscientists.com/HTML/content/news/news/743/

http://www.thenakedscientists.com/HTML/podcasts/show/2007.06.10-1/

[impaul]

Maybe sometimes we should review the concept of what is "life".

[another_someone]

George, you were saying that DNA needs water? Please can you explain this, and whether the lithoautotrophs described by JimBob therefore need water in the first instance.

OK, probably I should have said more accurately that organic enzymes (proteins and RNA) require to be suspended in water in order to work (in order to create the shapes they need to do their job).  Dehydrated proteins simply don't work - they will not be folded correctly.

Since DNA translates into RNA and proteins, and the translation process itself requires enzymes, thus DNA in the absence of proteins is non-functional.

[another_someone]

Maybe sometimes we should review the concept of what is "life".

http://www.thenakedscientists.com/forum/index.php?topic=2701.msg21842#msg21842
http://www.thenakedscientists.com/forum/index.php?topic=5620.msg55431#msg55431
http://www.thenakedscientists.com/forum/index.php?topic=3765.msg30138#msg30138
http://www.thenakedscientists.com/forum/index.php?topic=5396.msg53699#msg53699
http://www.thenakedscientists.com/forum/index.php?topic=7216.msg74910#msg74910