Arctic microbes spend 100 million years in frozen sleep before waking up again

Bacteria found on the bottom of the Arctic Ocean might have the longest life-cycle on Earth, surviving for as much as 100 million years in hibernation while waiting for the ice to thaw enough for them to be viable again.

These remarkable creatures were discovered when researchers at the UK's Newcastle University were testing sediment samples taken from the sea floor near the Arctic island Svalbard. Based on previous experiments, they expected gradual heating of the sediment to reveal a spike of microbe activity at the colder temperatures, but none at anything much hotter than 70 degrees Fahrenheit.

As expected, there was a spike of microbial activity at around that temperature, then a drop-off as the temperature increased. But then something shocking happened: microbe activity picked up again as the sediment hit 100 degrees, reaching a highpoint of activity at 125 degrees. What were these bacteria that thrived at such scorching temperatures - known as thermophiles - doing on the Arctic sea floor?

Analysis of the microbes' DNA revealed they were closely related to bacteria found in the hot, almost oxygen-free regions of the ocean's crust. Casey Hubert, one of the leaders of the research team, hypothesizes that changing sea currents might have carried them away from their tiny niches and into the wider Arctic Ocean, where they were forced to enter a period of dormancy in order to survive. At that point, the microbes had to just wait for temperatures to increase enough for them to wake up.

Here's the really crazy part - it might have taken 100 million years for that to happen. The microbes that became active when the researchers warmed the sediment samples were the exact same microbes that went into hibernation all those millions of years ago.

It's difficult to know precisely how long those microbes were frozen in the Arctic sediment, but if they were even in the ballpark of 100 million years, then they might be the longest-lived creatures on Earth. (Although it's worth mentioning the credible but disputed claim that 250 million year old bacteria were revived from New Mexico salt deposits.)

And it's worth remembering that the only reason the microbes were revived at all is humans happened to dig them up - who knows how long it will take their fellow bacteria still buried in the sediment to find the right conditions to wake up. If they're going to need the bottom of the Arctic Ocean to reach temperatures near 125 degrees, then they could be in for a wait that makes 100 million years look like a catnap.

[Environmental Microbiology via New Scientist]