Thought lifeless, seafloor crawling with microbes

BEIJING, June 2 (Xinhuanet) -- Long thought to be an undersea desert with little or no life, researchers now say the seafloor is crawling with microbes.

Scientists have found "thousands of times more bacteria on the seafloor than in the water above," according to a statement. The findings were made at two sites, suggesting rich microbial life extends across the ocean floor, said University of Southern California geomicrobiologist Katrina J. Edwards.

These results, along with a separate discovery announced last week of life a mile below the seafloor, have scientists wondering if life on Earth began along shorelines or perhaps originated in the oceans' depths.

Using genetic analysis, Edwards and colleagues found higher microbial diversity on common, basalt rocks compared with other marine locations, such as those found at hydrothermal vents. The diversity on the seafloor rocks was as rich as that in common farm soil.

"We now know that there are many more such microbes than anyone had guessed," said David L. Garrison, director of the National Science Foundation’s biological oceanography program.

The big question now is where all these newfound bacteria get the energy they need to survive.

"We scratched our heads about what was supporting this high level of growth when the organic carbon content is pretty darn low," Edwards said. Perhaps, the researchers figured, chemical reactions with the rocks themselves might offer fuel for life. Lab tests confirmed the idea.

The research supports the idea that some bacteria survive on energy from the crust, a process that could affect knowledge about the deep-sea carbon cycle and even the evolution of early life. This work should shed light on whether the bacteria evolved from ancestors that floated down from above or from some as yet unknown source deep in the crust.

(Agencies)