By Henry Fountain, May 27, 2008, The New York Times – Down below the ocean, there are some things that are very real — namely, bacteria and archaea. By some estimates, sub-seafloor prokaryotes may account for two-thirds of the biomass of these types of organisms on Earth.

The latest evidence for such a huge undersea biosphere, and a depth record of sorts, is reported in Science by R. John Parkes of Cardiff University and colleagues. They have found living prokaryotes 5,335 feet below the ocean floor off Newfoundland, about twice as deep as the previous record.

Intact cells were found in cores drilled through sediments up to 111 million years old, although the age of the prokaryotes themselves is an open question. The researchers were able to amplify genetic material, which strongly suggests that the cells are living, feeding on trapped methane, other hydrocarbons and organic carbon. Prokaryotes are simple organisms without a nucleus; they are an organism whose DNA is not contained within a nucleus, e.g. a bacterium.

Temperatures of the deepest core samples were estimated from 140 to 212 degrees Fahrenheit, so the cells qualify as extremophiles, able to withstand harsh conditions like those found around deep-sea hydrothermal vents. Some of the genetic sequences found match those from known heat-loving bacterial strains like Pyrococcus.

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Pyrococcus

Living cells have been found at greater depths under land, but the concentration of cells in the undersea cores (about a million per milliliter) is much higher. The finding is another that stretches the boundaries of where life can flourish — with all that implies about the situation on worlds other than Earth.

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