The 100-Million-Year Sleep –Earth’s Longest Hibernation Cycle (Today’s Most Popular)

Bacteria in arctic With a hibernation period of up to 100 million years, bacteria discovered on the Arctic sea floor may have longest life cycle of any known Earthly organism. Casey Hubert from the Geosciences Group at Newcastle University, UK, and colleagues discovered the bacteria while studying biological activity in sediment samples from the sea floor off the Norwegian island of Svalbard.

Hubert's theory proposed that rising currents thrust some cells out of their deep hot niche and into the cold Arctic seawater, where they lie dormant. The sediment buries them until the temperature rises enough for them to germinate –- a bio-cycle that could take up to a 100 million years.

The team expected to find organisms that flourish in the cold, but are killed at higher temperatures. While there was a peak of microbial activity in the sediment at a warm 20 °C, they found to their surprise that the graph began to pick up again beyond 40 °C, and there was a second peak of biological activity at around 55 °C. A completely unexpected class of heat-loving microbes, thermophiles, had been embedded in the sediment as spores and only germinated as the temperature approached 50°C.

A look at the genetic sequences of the thermophiles revealed that they are most closely related to bacteria from ecosystems in the warm, oxygen-depleted depths of oceanic crust or subsurface petroleum reservoirs. 

"It's like there's a seed bank in the sediment of diverse thermophiles," says Hubert. These spores can remain viable for millions of years, he says, and so might wait-out the burial period and long migration down into the warmer subsurface. "This could explain how thermophiles colonise these subsurface niches and populate the deep biosphere," he says.

Geomicrobiologist John Parkes of Cardiff University, UK, offered an alternative explanation in an interview with New Scientist. "The entire ocean is circulated through deep oceanic crust about every million years," he says, "so buried sediments could be inoculated as this fluid flows through them on its return to the ocean."


Casey Kazan via New Scientist

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