THE idea that a person could be cryogenically frozen and then revived tens or hundreds of years later is still in the realm of science fiction. For some microbes, however, it is reality. Known as psychrophiles – literally, lovers of ice – they can survive at extremely cold temperatures for hundreds of thousands of years. Though frozen parts of the world such as Antarctica and Siberia appear comatose and desolate, they are actually vast reservoirs of creatures in a state of suspended animation, and in some cases they are not suspended at all, but fully functioning living organisms.
In fact, it appears these things can actually thrive in such conditions. Researchers have found evidence – in the form of methane, for instance – that bacteria and other microbes metabolise while buried deep in ice and permafrost. Down to about -20 °C, thin films of unfrozen salty water remain, and these allow cells to take in nutrients and expel waste products by diffusion. Below -20 °C, there is no unfrozen water and metabolism is impossible. You can find more details in Life in Ancient Ice, edited by John D. Castello and Scott O. Rogers (Princeton University Press, 2005).
Just how extreme does it get for psychrophiles? There seems to be no limit. Biologists have found living fungi, bacteria, viruses, prokaryotes, green algae and yeasts buried up to 4 kilometres deep in solid ice. What is really amazing is how long they can live. Microbes more than 400,000 years old have been discovered in Antarctic ice, and several million years old in permafrost.
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What happens when the ice melts? The more gradual the thaw, the more likely it is that microbes will survive. As global warming causes glaciers to melt, the number of microbes flooding back into the environment is mind-boggling, estimated at 1017 to 1021 organisms a year.
The big question is, what happens to these things when they re-enter the world? Do they die because they cannot adjust to their new surroundings, or do they reproduce and spread, pouring ancient genes back into the gene pool? No one knows. But here’s a scary thought: if viruses that we thought had disappeared, such as those causing smallpox or the Spanish flu, have been frozen in the ice and re-emerge one day, they could in theory trigger an epidemic – to say nothing of other pathogens that we’ve had no contact with for millennia, and to which we would have no immunity. According to researchers, we shouldn’t rule it out.
