Life At -196°C

[Admiral Valdemar]

This week's New Scientist has a nice article I've just finished reading on the prospect of life at temperatures thought originally to be too low for life to exist, even dormant. According to the paper published in Cyrobiology, there has been measured energy dependant enzymatic activity in a species of arctic bacteria known Colwellia 34H even in liquid nitrogen.

Now, they may not be doing a whole lot there, but if this is the shape of things, it means that there is no minimum temperature for psychrophiles to live in. This means you can imagine life existing on Mars, Titan, Europa, Phobos, wherever really. And, what's more, they may be able to live forever at this rate given biological repair mechanisms need not work as hard with such low energy states because damage itself is directly proportional to temperature too.

I find this quite fascinating, since it means even the most frigid world could one day get warmed up by a growing star and thrive thanks to normally inactive bacteria in the ice caps.

[Lord of the Abyss]

And, what's more, they may be able to live forever at this rate given biological repair mechanisms need not work as hard with such low energy states because damage itself is directly proportional to temperature too.

Not true; cosmic rays and local background radiation constantly cause damage; if they can't keep up with that damage they will perish. I saw that pointed out in an article about the bacteria that live under the surface of rocks in Antarctica; they live so slow that they can be killed that way.

[Admiral Valdemar]

Not true; cosmic rays and local background radiation constantly cause damage; if they can't keep up with that damage they will perish. I saw that pointed out in an article about the bacteria that live under the surface of rocks in Antarctica; they live so slow that they can be killed that way.

Explain how these cosmic rays penetrate several klicks of ice and permafrost in sufficient density then and how samples of live bacteria over 200,000 years old from Lake Vostok also disprove this nonsense? The cell isn't replicating, so no DNA damage will manifest as lethal mutations anyway, not to mention the structure of a cell at that temperature is pretty much immutable to all but hard X-rays or above. If what you say is true, then NO bacteria should be alive from such a cold slumber.

Yet, the bugs swimming in several vials across the globe show otherwise.

[Lord of the Abyss]

Explain how these cosmic rays penetrate several klicks of ice and permafrost in sufficient density then and how samples of live bacteria over 200,000 years old from Lake Vostok also disprove this nonsense?

"Several klicks" ? The rocks are on the surface in the Dry Valleys, not under the ice. The bacteria themselves a just beneath the surface of the rocks as well. Besides which, there's the background radiation in the rocks themselves.

The cell isn't replicating, so no DNA damage will manifest as lethal mutations anyway, not to mention the structure of a cell at that temperature is pretty much immutable to all but hard X-rays or above. If what you say is true, then NO bacteria should be alive from such a cold slumber.

First, the radiation damages all parts of the cell, not just DNA; with a metabolism that slow, the damage matters. Second, they are not "slumbering"; they just have a very, very slow metabolism. Third, I never said they all died; just that it was a cause of mortality.

[Admiral Valdemar]

"Several klicks" ? The rocks are on the surface in the Dry Valleys, not under the ice. The bacteria themselves a just beneath the surface of the rocks as well. Besides which, there's the background radiation in the rocks themselves.

I'm talking about extremes from the North Pole to the surface of Europa here. There are even shallower excavations of far greater age, such as 60 metres into the permafrost in Siberia which would be around 3 million years old. Besides, if the bacteria can survive under a glacier in Antarctic, then they'll have even better chances below ice several klicks beneath the surface, far from all but the most penetrating (and thus least harmful) radiation.

First, the radiation damages all parts of the cell, not just DNA; with a metabolism that slow, the damage matters. Second, they are not "slumbering"; they just have a very, very slow metabolism. Third, I never said they all died; just that it was a cause of mortality.

At that temperature and depth, the radiation will do jack to anything but the most sensitive parts of the cell. You're talking massive damage here, like decimating the ribosomes, plasmalemma and nucleus etc. That would be far more likely to happen closer to the surface, yet we see that bacteria a fraction of the age of some being looked for in new expeditions have survived easily enough. They can, to a limited degree, repair at low temperatures, but it tends to not matter since the extreme cold and ice or other frozen material helps absorb damaging rays. Background radiation would be negligible here unless near a hotspot of radon or uranium.

[spikenigma]

it's a shame the Jupiter Icy Moon Orbiter was cancelled

how knows what is under the ice

[Admiral Valdemar]

I'm pretty sure ESA has something in the works, though NASA is going to go and explore some of the oceanic planets and moons, as it were, as soon as we get a decent nuke powered craft and submersible and remove the bean counters currently in.

[Ravencrow]

Have they managed to study the properties of the enzymes in these bacteria? I'll be interested in finding out how they work at these low temperatures and what sort of rates.

[Admiral Valdemar]

The secreted enzyme compound is an exopolymer similar to xanthum gum in how it keeps the freezing point of water down well below -50 or so degrees, probably around -200.

[Kwizard]

Not to go off on a tangent, but could that exopolymer be mass produced in the same way insulin is? It sounds pretty useful unless it's got toxic or corrosive properties. Or is it already being used?

[Admiral Valdemar]

I don't see why not. But if it does the same thing as a gum already used in the food industry, it's of little use to us. I can't recall any other properties of the substance other than simply lowering the freezing point of water by a significant degree.

[CaptainChewbacca]

If they want to explore an icy, undiscovered, underwater world they could start with Lake Vostok. Good for practice.