Magazine article Science News

Bacteria Alive and Thriving at Depth

Magazine article Science News

Bacteria Alive and Thriving at Depth

Article excerpt

Bacteria alive and thriving at depth

In recent years, scientists have found bacteria, a far down as 1,150 feet, in wells that penetrate deeply buried aquifers -- porous layers of rock that hold underground water. Such finds have forced hydrologists to question their traditional belief that deep aquifers were void of life. But it was not clear whether these bacteria were native residents of the aquifers or just contaminants from the world above, living solely within the wells. Moreover, no one had established how the bacteria were affecting their environment, if at all.

Experiments are now demonstrating for the first time that bacteria are indigenous to deep aquifers and that they actively change the chemistry of the groundwater, reports a group of hydrologists and microbiologists.

"The bacteria do a lot. They are probably one of the most important processes in determining groundwater chemistry," says Francis H. Chapelle of the U.S. Geological Survey (USGS) in Columbia, S.C., who conducted the experiments along with USGS colleague Peter B. McMahon, James T. Morris of the University of South Carolina in Columbia and Joseph L. Zelibor Jr. of the University of Maryland in College Park.

In a set of experiments near Hilton Head, S.C., Chapelle and his colleagues drilled more than 100 feet down into an aquifer and pulled up sediment cores, from which they isolated bacteria that were attached to the particles of sediment. In the laboratory, the researchers incubated the bacteria and demonstrated that the organisms metabolically produced carbon dioxide under both aerobic and anaerobic conditions, according to a report in the February GEOLOGY. Groundwater typically contains dissolved carbon dioxide gas.

The scientists could relate this laboratory-produced gas, by means of a peculiar isotopic signature, to that found dissolved in water from the aquifers. …

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