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http://www.aaas.org//news/releases/2008/0522microbes.shtml
Heat-loving Microbes Thrive Way Down Deep
![[PHOTOGRAPH] Thermococcus chitonophagus [Image courtesy of Integrated Ocean Drilling Program, Texas A&M University]](/news/releases/2008/images/0522microbes.jpg "[PHOTOGRAPH] Thermococcus chitonophagus [Image courtesy of Integrated Ocean Drilling Program, Texas A&M University]")
Thermococcus chitonophagus
[Image courtesy of Integrated Ocean Drilling Program, Texas A&M University]
Sediment from below the sea floor of the northern Atlantic Ocean reveals living and thriving microbes at deeper depths than any other population documented before.
In the 23 May Science, a Brevia report shows prokaryotic cells from 1626 meters below the sea floor where the temperature ranges from 60 to 100 degrees Celsius (140—212 degrees Fahrenheit). The cells, which lack cell nuclei, were living in sediment samples ranging in age from 46 million to 111 million years old.
Previously, it was suggested that the sub-sea-floor biosphere could contain two-thirds of the Earth's prokaryotic mass. But prokaryotes had only been observed as deep as 842 meters, where 3.5 million year old sediment contained cells living in a 55 degree Celsius environment. To justify the assertion that so many cells exist beneath the sea floor, samples had to be taken from deeper depths.
Lead author Erwan Roussel and his coauthors found living microbes in nine sediment samples obtained from the Newfoundland Margin. The number of cells correlated with the amount of organic matter, implying that "some of the cells were metabolically active," wrote Roussel and his coauthors in Science.
![[PHOTOGRAPH] The JOIDES Resolution, a drilling ship [Image courtesy of Integrated Ocean Drilling Program, Texas A&M University]](/news/releases/2008/images/0522microbes_ship.jpg "[PHOTOGRAPH] The JOIDES Resolution [Image courtesy of Integrated Ocean Drilling Program, Texas A&M University]")
The JOIDES Resolution approaching the Royal Naval Dockyard, Bermuda.
[Image courtesy of Integrated Ocean Drilling Program, Texas A&M University]
The microbiologists also observed that nearly 5% of the cells were dividing. The proportion of dividing cells was even higher—at nearly 12%—in the deepest sample. Dramatic increases in energy sources, such as methane and higher hydrocarbons, are the likely reason for greater cell division deeper below the seafloor.
Analysis of the cells' genetic material revealed sequences of some known heat-loving organisms. The researchers, based at the Université de Bretagne Occidentale in France and Cardiff University in the United Kingdom, propose that the microbes may be of the Archaea variety and that the so-called thermophiles "can dominate deep and hot sediments where there are thermogenic energy sources."
22 May 2008
