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A new group of microorganisms believed until recent years to exist only in extreme ocean environments has been discovered in waters off Oahu. Ocean’s extremophiles
not so extreme, after allBy Helen Altonn
Star-Bulletin
The organisms, known as archaea, weren't expected in such a habitat "and certainly not in the numerical abundance that we found them," said University of Hawaii biological oceanographer David M. Karl.
"They may, in fact, be one of the most abundant organisms in the sea, but beyond that we know very little about them."
Markus Karner, post-doctoral researcher in the UH Department of Oceanography, Edward DeLong of the Monterey Bay Aquarium Research Institute in California and Karl discovered the archaea at a site called Station ALOHA, 60 miles north of Oahu.
Their findings are reported in the current issue of the journal Nature.
Karner, lead author of the paper, said in an interview that they started with a past assumption that archaea, unlike bacteria, are confined largely to harsh environments.
Historically, he said, the organisms were found in very saline, high-temperature or high-pressure areas, such as the hydrothermal vents at seamount Loihi off the Big Island.
Those microorganisms -- known as extremophiles -- are being investigated by Marine Bioproducts Engineering scientists at UH-Manoa and the University of California-Berkeley for potential use in new drugs and other products.
Karl, one of the discoverers of archaea at Loihi, said, "There was a misconception that these things are kind of ancient ... relics of time gone past because most lived in weird environments.
"These clearly are habitats for archaea, and we were misled to think they were the only place they lived."
In 1992, however, DeLong reported in a paper published by Nature magazine that archaea also are found in marine plankton. He identified them in samples collected in Antarctica where UH scientists do a lot of work, Karl said. "It created quite a stir."
But DeLong could only extract nucleic acid from ocean plankton to see how much of it was archaeal or bacterial, Karl said.
"He did it on a very broad scope and didn't really know how many organisms there were or how they looked or if there were any at all. It might have just been DNA."
DeLong then spent five years developing a breakthrough method of identifying the cells with fluorescent probes, Karl said.
He turned to the UH scientists, who applied the new tool to an Ocean Time-series program off Oahu. They began studying ocean and atmospheric systems and microbial life at Station ALOHA in 1988 to get a continuous record of variations.
They spent a year looking at the ocean to build a record of archaeal populations, which are in great abundance in the mesopelagic zone of the water column, Karl said.
This zone -- about 400 to 500 feet below the ocean's upper, lighted layer -- is very important, but hasn't been studied much because it's in the middle, he said. He calls it the twilight zone because there is light but not enough for photosynthesis.
Karner said, "We ended up finding, except for surface waters, that archaea are a very common component of the microbial system of the water column." In deeper waters, they made up 30 percent to 50 percent of total microorganisms, he said.
Two archaeal subgroups were identified and if Station ALOHA is characteristic of the ocean in general, Karl said, archaeal cells are nearly as abundant globally as bacterial cells.
"And we don't even have these cells in culture so we don't even know what they're doing," he added.
An aggressive research effort is under way by three UH students in the laboratory to try to grow the cells and learn more about what they do, Karl said.
It was believed that they were a forerunner to bacteria, but they're not simple organisms -- they're advanced, Karl said. "They are the third domain of life."
UH microbiologist Maqsudul Alam and his group for the first time have cultivated extremophiles from hydrothermal vent water samples.
The challenge now is to culture archaea from the open ocean to learn their physiology and capabilities and better explain the system to avoid surprises in its behavior, Karner said.
"If we find archaea numerically important, it means a fairly unknown type of organism constitutes a fairly big chunk of the whole system," he said. "And you want to know more about it because maybe you are making assumptions about the system which are not holding."
For example, archaea could either be creating or consuming methane, a greenhouse gas involved in global warming, Karner noted. "We can't re-engineer the whole ocean. It's absolutely necessary to know how the system works to know what can be done, what are the possibilities."
Archaea populations also could be beneficial to mankind for pharmaceutical or neutriceutical products, and scientists won't have to go to deep sea hydrothermal vents to find them, Karl said.
"Maybe a treasure chest of organisms is a lot more accessible than we thought it was."
University of Hawaii
