Secrets from the Sea Floor
With Funding from Washington Sea Grant, UW Oceanographer John Baross
Finds Meaning in Microbes from Hydrothermal Vents
In 1977, science got its first glimpse at a strange, previously unknown world near the Galapagos Islands of Ecuador. At this site, several thousand feet beneath the Pacific Ocean's surface, was a menagerie of unexpected life forms — giant tubeworms, shoesized clams, transparent octopuses and ghostly white crabs.
Oceanographers, biologists and chemists rushed to the Galapagos site, eager to learn more about this eerie oasis on the relatively barren sea bottom. With the subsequent discovery of similar sites scattered across the seafloor, the scientific community discarded many previously held notions about the limitations of life beneath the wavers.
Most of the newly discovered creatures draw sustenance from nutrients, including sulfur compounds and carbon dioxide, mined from the rocks by hot water that emanate from geothermally heated fissures known as hydrothermal vents.
The water that flows from these vents can reach temperatures of 570 degrees Fahrenheit, while the pressure at these depths can be in excess of 7,000 pounds per square inch.
Experiences with Extremophiles
For University of Washington professor John Baross, the most fascinating ingredient in this unusual formula for life are the microscopic sulfur-eating bacteria and other microbes that are the foundation of this complex food web. Collectively known as extremophiles, these microbes can endure the harshest of conditions. Their counterparts in other environments have been plucked from the boiling waters of geysers and hot springs, chipped out of mile-thick glacial ice and nabbed in the super-salty environment of the Dead Sea.
Baross's experience with extremophiles began in 1979, two years after the Galapagos vents were first sighted. With funds from Oregon Sea Grant, he was able to join the crew of a research vessel bound for a freshly discovered hydrothermal vent off the coast of Mexico. He was the sole microbiologist aboard ship, Baross recalls.
"At that time, I was primarily interested in human pathogens, such as Vibrio species, the causative agents of cholera and other shellfish-borne diseases," he says. "But the site of 'black smokers' spewing liquid water at three times the boiling point of water at surface conditions changed my research focus to testing the idea that microbes could live at super-heated temperatures. The rest is history and I started collecting the high-temperature microbes near the vents for further studies in the lab."
"In those days, there were less than a dozen researchers interested in this topic," Baross remembers. "However, by the mid-1980s, the field had grown to include hundreds of people. With today's high-tech interest in extremophiles, there's been a virtual renaissance, with thousands of people studying the properties of these unusual microbes."
Most of the current interest is directed toward the applied aspects of deep-sea extremophiles. Whether in the production of artificial sweeteners or as the cornerstone of the Polymerase Chain Reaction (or PCR) for cloning DNA in the laboratory, enzymes derived from extremophiles have already revolutionized modern technologies. The possibilities may be as numerous as the individual strains of extremophiles themselves. With continued support from Washington Sea Grant, Baross and his students have identified dozens of these organisms, including new genera.
"The properties of these extremophiles have potential for use in a number of so-called 'green' industrial processes — environmentally friendly methods for mining for metals, extracting oil or making paper from wood pulp, for example," Baross says.
The biggest challenge, according to Baross, lies in devising technologies for keeping extremophiles alive in a laboratory. More than 99 percent of all bacteria cannot be grown in laboratory cultures, so scientists know almost nothing about them. Mimicking deep-sea conditions is extremely difficult, whether meeting the needs of monocultures or tightly linked communities of extremophiles.
Clues to the Origins of Life
While he and his students continue to identify new species of microbes and devise technologies to help explore their potential uses, Baross has taken his interest in extremophiles in a new direction. Working with the UW's Astrobiology program, he is looking at ways that these microbes may have shaped life on our planet and, possibly, on other celestial bodies. Conditions in our planet's primordial seas may have been similar to those surrounding hydrothermal vents, favoring the birth and evolution of organisms that can survive under high heat and pressure.
"It's somewhat of an oversimplification to say that the extremophiles we study, in particular, the microbes collectively known as archaea, are 'living fossils'," Baross points out. "Even these organisms have undergone gradual change over the millennia. Nonetheless the archaea are deeply rooted in our evolutionary tree."
How deeply? The hydrothermal vents probably appeared 4.2 billion years ago, as soon as the first liquid water coalesced on our geothermally active planet, Baross explains. At that time, the Earth's surface was bombarded with meteors and other extra-planetary debris. With some of the larger bombardments, the impacts were sufficient to vaporize all forms of surface water. The vents may have served as oases, capturing water in their fissures and sustaining the earliest forms of life — microbes — until condensation could replenish the primordial seas.
The recent discovery of the Lost City, a phenomenal hydrothermal vent field on the mid-Atlantic Ridge with more than 30 active and inactive outlets, has stretched our already expansive understanding of life on Earth. Unlike most conventional forms of life, the extremophiles from this highly alkali (pH 10) environment "breathe" methane instead of oxygen.
"We need to put these microbes in culture, so we can observe them and better understand the processes with which they have filled such an unusual niche," Baross says. "Thanks to Washington Sea Grant's assistance, we are making steady progress, opening new doors to both theoretical and applied realms."
Winter 2006
Contact David G. Gordon, Science Writer for Washington Sea Grant, for further information.