Printed from “The Discovery of Hydrothermal Vents - 25th Anniversary CD-ROM” ©2002 Woods Hole Oceanographic Institution

INTO THE FUTURE: Life in Extreme Environments

Life beneath the seafloor
The amazing discovery of life flourishing at hydrothermal vents ushered in new ideas of where and how life could exist. Scientists have now found species of microorganisms that have adapted to high pressure, unusual or toxic chemicals and minerals, low supplies of nutrients, and high (113°C or 235°F) temperatures. They are called extremophiles (“extreme lovers.”) Under a wide range of conditions, life seems to find ways to survive.

The 1991 discovery of “snow blower” vents blasting white bacterial matter into the ocean opened up another previously unimagined possibility. Scientists are now exploring whether potentially huge communities of microorganisms are living in reserviors in the cracks and crannies below the seafloor! This so-called “deep biosphere” may be as large as the biosphere on Earth’s surface.

When submarine volcanic eruptions occur on mid-ocean ridges, subsurface waters heat up and microorganisms beneath the seafloor go crazy. They reproduce at extremely high rates. Huge volumes are carried out through openings in the seafloor and dispersed into bottom waters.

The bacteria also produce the white mats of “snow blower” debris that cover the seafloor, as snow covers a mountain. WHOI biologists Craig Taylor and Carl Wirsen showed how these bacteria use the hydrogen sulfide in vent fluids to make solid, white, sulfur filaments. Large populations of these bacteria link these filaments together to produce mats, which help keep the bacteria attached to rocky surfaces. In this way, they stay bathed in life-sustaining (for them at least!) hydrothermal fluids percolating from the ocean crust. (The bacterial mats may also form a layer of carpeting around vents that encourages animal such as Pompeii tubeworms to settle down and grow.)

Marvelous microbes
Many species have adapted to extreme conditions in ingenious ways—like the Pompeii worms that survive the high temperatures on the side of black smoker chimneys, or tubeworms that maintain bacteria farms inside of them. Scientists have found many examples of deep-sea, single-celled microbes that have unusual features or make use of unusual chemical processes. They are well adapted to carve out a niche where they can thrive, but other species cannot.

Some of these adaptations have proved useful to people. Only a few years ago, scientists found a previously unknown microbe living in a hot spring in Yellowstone National Park. The microbe had a heat-resistant enzyme. That enzyme was the key to a chemical reaction that has given scientists new-found ability to reproduce large amounts of DNA. It launched a revolution in biotechnology.

Heat-resistant enzymes from microbes found at seafloor vents have been used similarly for useful purposes. And there are many other examples of adaptations in “extreme” microbes that are important to our society and economy.

For example, the mining industry uses huge vats filled with microbes that naturally dissolve rocks into acid. The microbes actually do the work of extracting valuable minerals out of ores. The food industry adds bacteria that secrete a certain binding substance to ice cream to help maintain its texture. Oil-eating bacteria are used to clean up oil spills. What other organisms will we find in extreme environments with unusual features that will lead to useful products or life-saving drugs? The ocean floor holds enormous potential for discoveries that could improve our lives.