Bacteria 'feed' on earth's ocean-bottom crust

Rocks on and under seafloor offer feast for microbes

Rocks made of basalt on and under the ocean bottom harbor surprising numbers of deep-sea bacteria. Click here for more information.

Seafloor bacteria on ocean-bottom rocks are more abundant and diverse than previously thought, appearing to "feed" on the planet's oceanic crust, according to results of a study reported in this week's issue of the journal Nature.

The findings pose intriguing questions about ocean chemistry and the co-evolution of Earth and life.

Once considered a barren plain dotted with hydrothermal vents, the seafloor's rocky regions appear to be teeming with microbial life, say scientists from the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Mass., University of Southern California (USC) in Los Angeles, and other institutions.

Scientists have found that rocks beneath the seafloor are teeming with microbial life. Click here for more information.

While seafloor microbes have been detected before, this is the first time they have been quantified. Using genetic analyses, Cara Santelli of WHOI, Katrina Edwards of USC, and colleagues found three to four times more bacteria living on exposed rock than in the waters above.

"Initial research predicted that life could in fact exist in such a cold, dark, rocky environment," said Santelli. "But we really didn't expect to find it thriving at the levels we observed."

Surprised by this diversity, the scientists tested more than one site and arrived at consistent results, making it likely, according to Santelli and Edwards, that rich microbial life extends across the ocean floor.

"This may represent the largest surface area on Earth for microbes to colonize," said Edwards.

"These scientists used modern molecular methods to quantify the microbial biomass and estimate the diversity of microbes in deep-sea environments," said David Garrison, director of the National Science Foundation (NSF)'s Biological Oceanography Program. NSF's Ridge 2000 program funded the research. "We now know that this remote region is teeming with microbes, more so than anyone had guessed."