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"An understanding of cold-adapted bacteria could offer valuable insights into the origins of life on Earth and the possible habitability of other celestial bodies."

The Persistent Professor: Jody Deming Carves a Crucial Niche in Cold Seas

By David Gordon

Worldwide, the mean water temperature of the sea floor is about three degrees Centigrade, barely above the freezing point of seawater. These cold, deep waters exist under very high pressures, reflecting the weight of the ocean above. At the ocean's surface, in polar regions where sea ice forms, the liquid brine pockets within the ice can reach a mind-numbing −35 degrees C and still remain liquid due to their extreme saltiness.

Yet despite the inhospitable natures of such environs, certain strains of bacteria can - and routinely do - survive and grow. Both cold-adapted (or psychrophilic) and pressure-adapted (barophilic) bacteria are the dominant forms of active life on the ocean floor.

What allows such bacteria to function under conditions of cold and high pressure? The answer, says Professor Jody Deming, a Washington Sea Grant-funded scientist, lies in some of the unique enzymes that these microorganisms produce.

Typically, enzymes perform best over a range of temperatures, from room temperatures to well above human body temperatures. Most of the well-studied enzymes from psychrophilic microbes also perform optimally within the same range. However, in her University of Washington (UW) laboratory, Deming and her students have isolated several enzymes that can function efficiently down to −1 degree C. After several years of study, the search has shifted to bacterial enzymes that can work at temperatures far below the freezing point.

Deming is particularly interested in the bacterial production of exopolymers - complex organic compounds that serve as a means to stabilize enzymes so they can continue to be active, even as water molecules freeze around them.

"The exopolymers act as anti-freeze compounds," offers Deming. "Enzymes that are critical to bacterial survival in Arctic sea ice can continue to do their work if they are embedded in a cell coating of exopolymers that protect both the enzymes and the cells from freeze-damage," she explains.

Low-temperature enzymes have already shown their worth in the biotechnician's laboratory. They are helpful to the Ligase Chain Reaction, used routinely as part of the medical molecular biologist's tool kit for connecting pieces of DNA. They have incredible potential for enriching our daily lives, too. For instance, as active ingredients in coldwater laundry detergents, they could gobble up fats and oils at much lower temperatures than existing detergents, conferring energy cost savings to their users.

(Top) To protect herself from sub-zero temperatures and fierce Arctic winds, University of Washington Professor Jody Deming hides behind the fur-lined hood of her insulated parka. (Photo by Shelly Carpenter) (Bottom) Striving to better understand cold-adapted bacteria, Professor Jody Deming removes a core sample of super-frigid Arctic sea ice (Photo by Eric Collins)

"We're presently collaborating with a Seattle-based biotech firm, that is looking at ways to freeze fish eggs without harming them," says Deming. New exopolymers that originate from cultures in her laboratory could enable the firm to safely ship frozen but viable eggs to hatcheries and other facilities around the world.

Perhaps as important, an understanding of cold-adapted bacteria could offer valuable insights into the origins of life on Earth and the possible habitability of other celestial bodies.

"Among the best candidates for finding microbial life elsewhere in our solar system are the planet Mars and Europa, one of Jupiter's moons. The surface of Mars is frozen," notes Deming. "So is Europa's surface," she adds, "where conditions dip as low as −160 degrees C."

With all this in mind, Deming has recently expanded her academic focus. In addition to her work with the UW School of Oceanography, she is also a professor in the university's newly created Astrobiology Program.

In recognition of her body of work, Deming was recently honored with membership in the National Academy of Sciences, the nation's most prestigious organization of scientists. Clearly persistence has paid off - for psychrophiles and the professor who, with help from Washington Sea Grant Program, has made their study her life's work.

[2/7/05]

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