Life found 'on margin of existence'

Joides Resolution has been drilling off South America

By Dr David Whitehouse BBC News Online science editor

An international team of biologists and geologists are drilling into the sea floor off the coast of South America to recover live bacteria that do not need sunlight, carbon dioxide or oxygen.

They exist in such extreme conditions that the microbes may hold clues as to how life might survive on other worlds.

"The implications of this mission are exciting," said Jack Baldauf, deputy director of the Ocean Drilling Program (ODP) at Texas A&M University, US.

"Earlier voyages have found specimens of these bacteria at depths of up to 800 meters (2,625 feet) below the sea floor, and we estimate that they may number between 10 and 30% of the Earth's biota.

Little known

"That means that the biosphere is larger than previously thought - it doesn't just stop at the sea floor."

Scientists are studying the rocks from under the sea floor

Other expeditions have obtained samples of these bacteria, but so far researchers know very little about their real numbers, their diversity, or their role in the biogeochemistry of the oceans.

In the past few weeks, the drilling ship Joides Resolution has been obtaining samples in the eastern equatorial and southeast Pacific.

Cores containing microbes have been obtained from previously drilled sites, chosen to represent different subsurface environments, such as methane-rich and normal oceanic environments.

"It's like walking into a tropical rainforest for the first time and beginning to identify and count the birds," said Tom Davies, at Texas A&M University.

Strangest ecosystem

Although it has been recognised in recent years that there is a great deal of living material in the rocks beneath our feet in the form of bacteria, hardly anything is known about the types of bacteria concerned or about how they change with depth.

"This type of microbiology is an entirely new science field. Such research raises questions about the presence of life in extreme environments on this planet and possibly other planets," said Jack Baldauf.

"ODP is uniquely positioned to sample one of the least known and potentially strangest ecosystems on Earth - the microbial biosphere of deep marine sediments and the oceanic crust.

"The growing international interest in the subsurface biosphere is driven by many factors, not the least of which is sheer fascination with the nature of life on the margin of existence."