Squeezed to the Extreme

Let's face it. When compared with a lot of organisms, humans are big wimps. We can't live in boiling water or on Antarctic ice, and we need special pressurized suits to survive the crushing weight of water at low ocean depths. We avoid these hostile places for the most part because we don't want to turn into boiled jelly, ice pops, or flattened pancakes. Yet, a multitude of microorganisms have no problem making themselves at home in these extremes.

Imagine pressure so great that a submarine is crushed flat. Load a column of water one mile (1.6 km) high over the top of the vessel and splat! Your submarine is now horizontal metal ready for the recycling bin.

Imagine going seven times deeper—to one of the deepest known spots on the ocean floor, the Marianas Trench in the Pacific Ocean, seven miles (11 km) below the surface. You won't find any submarines, but you will find bacteria called piezophiles (from the Greek words piezein, “to squeeze,” and philos, “loving”). Even at submarine-crushing pressures, these piezophiles aren't squeezed to death. Their name makes it clear—they “love” the pressure!

What special traits allow these bacteria to live under such high pressures? That's what a team of Japanese scientists wants to know. This group, called Deepstar, collects mud samples from ocean bottoms to hunt for piezophiles. Led by Dr. Koki Horikoshi, the Deepstar team uses underwater robots called submersibles to do the dirty work. One of the submersibles, the Kaiko, is capable of withstanding water pressures as deep as the Marianas Trench and has brought back more than 180 different types of bacteria.

Submersibles aren't the only man-made probes finding their way to the ocean floor. Drills mounted on ships are also cranking down to ocean bottoms searching for strange life forms. Right now, the best deep-ocean drill can reach only to four miles (6.5 km), and must operate in mild waters.

All that is set to change, though, as a joint scientific effort between the United States, Japan, and 20 other nations will open exploration of the deepest, most frigid ocean bottoms known. The U.S./Japan effort, called IODP (Integrated Ocean Drilling Program), formally began in April 2003. A new drill ship being built, the Chikyu, will be able to drill in any deep ocean location by 2008.

In the meantime, scientists like Dr. Horikoshi are studying the deep-sea piezophiles that submersibles have dug up. Understanding how these creatures successfully deal with high pressure is the scientists' aim.

Success at high-pressure living is at least partly due to the creatures' simple, one-celled structure. One-celled bacteria have no air pockets that collapse or rigid bone structures that break. Their small size protects them from bursting like water-filled balloons.

But it isn't enough to be small and one-celled, as a pair of U.S. scientists discovered.

Doctors Anurag Sharma and James Scott of the Carnegie Institution of Washington (Washington, DC) tested the ability of normal, surface-loving bacteria to live under the kind of pressures found at the ocean bottom. These researchers made a squeezing tool that not only put bacteria under deep-sea pressures, but also measured metabolic changes taking place inside the cells.

It turned out that an amazing 16 out of every 1,000 bacteria (1.6 percent) lived through the ordeal. This shows that bacteria are already capable of living a high-pressure existence. But because so many of the surface-loving batch didn't survive, the piezophiles must hold some secrets of high-pressure living that make them more fit for their ocean bottom home.

Those secrets are special adaptations that allow piezophiles to grow and reproduce under monstrous pressures. Scientists are only at the very beginning of understanding exactly what those adaptations are. It will take much scientific detective work to figure out the details. In the meantime, it's likely that these pressure-loving microbes won't just be scientific curiosities—they'll be put to work, too!

While industries have limited uses for whole bacteria, they do have needs for certain parts of these creatures. Examples are the proteins that run the metabolic machinery in bacteria. Called enzymes, these proteins can be pulled out of the bacteria and used for a variety of tasks. Enzymes may be useful in high-pressure food processing, in breaking down toxic waste, or as substitutes for harsh chemicals used in paper production.

Whether studying their structures or figuring out ways to put them to industrial use, scientists are convinced of the importance of investigating these bizarre microbes. Living their lives under pressures great enough to flatten a house, piezophiles have given the researchers a whole new way of pondering what makes a “home, sweet home.”

Vocabulary

metabolic:
Relating to the process by which living things change food into energy and living tissue.

microbe:
A very tiny living organism.

microorganism:
An organism, such as a bacterium, so small that it can be seen only by using a microscope.

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Activity

  1. In which zone of the oceanic biome do piezophiles live?
    [anno: They live in the oceanic zone.]
  2. How are piezophiles adapted to live in the Marianas Trench?
    [anno: The piezophiles are able to withstand an incredible amount of pressure.]
  3. Why are scientists interested in studying the piezophiles?
    [anno: The scientists hope to find uses for the bacteria or the bacteria parts, such as the enzymes. The scientists think the enzymes might be useful in high-pressure food processing, in breaking down toxic waste, or as substitutes for harsh chemicals.]
  4. Would you expect to find large organisms in the Marianas Trench? Why or why not? Write a few sentences to explain your answer.
    [anno: Answers will vary. Students might think that large organisms would not live in the Marianas Trench because it would be difficult to develop a skeletal structure that could support an animal under great pressure.]