Arctic bacteria may have the longest life cycle on Earth

Bacteria discovered on the Arctic sea floor may have longest life cycle of any known organism, as it has a hibernation period of up to 100 million years.

Casey Hubert from the Geosciences Group at Newcastle University, UK, and colleagues came across the bacteria while studying biological activity in sediment samples from the sea floor off the Norwegian island of Svalbard. What the team expected to find were organisms that flourish in the cold, but are killed at higher temperatures.

Sure enough there was a peak of microbial activity in the sediment at a warm 20 degree C, but then the graph began to pick up again beyond 40 degree C, and there was a second peak of biological activity at around 55 degree 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 degree C.

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

Hubert's theory, presented earlier this month at a Society for General Microbiology meeting in Nottingham, UK, proposes that rising currents thrust some cells out of their deep hot niche and into the cold Arctic seawater, where they lie dormant.

Sediment buries them until the temperature rises enough for them to germinate - but this could take up to a 100 million years. 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.