Deepest-living lifeform discovered

Microbes have been discovered thriving more than 5,000 feet below the ocean floor, making them the deepest living life forms known.

The primitive organisms inhabit a place where temperatures reach 100C.

They are thought to be archaea, a distinct family of non-bacterial microbe.

Scientists found the organisms in 100 million-year-old sediment samples drilled out of the ocean floor off Newfoundland, Canada.

The deeper samples were hot and contained high concentrations of methane and hydrocarbons, which can be used as an energy source by some organisms.

Intact living cells were found in all the samples, many of which were actively dividing. Like all bacteria and archaea, they were prokaryotes, meaning they did not carry their genetic material in a nucleus.

The researchers, led by Dr Erwan Roussel, from the Institut Universitaire European de la Mer in Plouzane, France, wrote in the journal Science: "These data provide direct evidence that significant prokaryotic populations are present in marine sediments at depths greater than a kilometre."

Genetic material from the organisms matched that of some known heat-loving microbes, or thermophiles.

Scientists believe they are a type of archaea that are adapted to hot environments and live off methane.

It has been suggested that two thirds of all the Earth's prokaryotes may live beneath the sea floor.

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