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Microorganisms on a Starvation Diet

International Research Team: Natural Radioactivity may supply Life Energy for Deep Biosphere Microbes
Microorganisms on a Starvation Diet
Natural Radioactivity may supply Life Energy for Deep Biosphere Microbes

An international research team from Germany and the US present their explanation how life could sustain in the Deep Biosphere. During an expedition with the drilling ship Joides Resolution in the Eastern Pacific an international team of researchers collected hundreds of samples by using novel sophisticated biogeochemical, molecular and microbiological approaches. After intensive analysis Bo B. Jørgensen and his colleague Steven D´Hondt now present in the journal Science a model explaining how the microbes could survive in a world deep down – shut off from the surface life. They could use the natural radioactivity as an energy source.

In earlier studies scientists have estimated that 10 to 50% of all biomass is buried deep in the sediments. Steven D´Hondt from the University of Rhode Island and Bo Barker Jørgensen from the Max Planck Institute for Marine Microbiology in Bremen, Germany confirm this range in their report for the Ocean Drilling Program. On leg 201 in the Eastern Pacific they detected living microbes down to 400 meter below the sea bottom. Their tests definetely proved that the microbes were alive and were not contaminants from the surface of the earth. In the topmost layer they counted up to 100 million cells per milliliter, much deeper in the 35 million year old layers near the earth´s crust the cell number dropped to 1 million. This produces a puzzle as only the topmost layers are in exchange with the surface world rich of carbon compounds. From where do the microbes get their daily lunch?
A fresh sediment core on deck of the Joides Resolution. The scientists protect themselves from the toxic Hydrogen Sulfide fuming out of the sediment. (Source: ODP Leg 201 Shipboard Scientific Party).
Taking a close look at the organic compounds deposited within these sediments, which may serve as an energy fuel for the cells, it is feasible to calculate that their life must be extremely slow. They can divide only once every thousand years. This long doubling time contradicts commonly held theories of life, as every cell has to maintain a set of housekeeping enzymes and other machinery, ready to start up when something to consume appears. As this machinery will never run idle for one thousand years, there must be an alternative energy source for the cells somewhere.

Based on their own data and measurements done by others, Jørgensen and D´Hondt suggest that for the most part of the Pacific Ocean this alternative energy may be supplied by natural radioactivity. Water molecules dissociate into hydrogen and oxygen molecules when hit by ionizing radiation from decaying isotopes of potassium, uranium and thorium. These isotopes are abundant in the sediments and may provide enough energy for the microbes. Tapping this power source the Deep Biosphere would be uncoupled from the surface life. The authors point out that this kind of exotic life could have evolved on others planets far away from stellar energy.

In December 2006 scientists from the Max Planck Institute will again join the group of Steven D'Hondt, this time on board the RV Roger Revelle in the central South Pacific. In this ocean region, far away from the continental shelves, extremely little organic material is buried into the sub-seafloor and radioactivity could possibly be the most important energy source.

Manfred Schlösser


Prof. Dr. Bo Barker Jørgensen
Phone: +49 421 2028 - 602
Fax: +49421 2028 - 690
E-mail: bjoergen

Prof. Dr. S. D´Hondt
Graduate School of Oceanography
University of Rhode Island
E-mail: dhondt

Press officer
Dr. Manfred Schlösser
Telefon: +49 421 2028 - 704
Fax: +49 421 2028 - 790
E-Mail: mschloes
B.B. Jørgensen and Steven D´Hondt . A Starving Majority Deep Beneath the Seafloor. Science, 10 November 2006.
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