Yellowstone virus startles scientists with ancient lineage


image A virus found in Yellowstone National Park thermal pools has a structure so ancient that scientists think it sits near the root of the universal tree of life, according to a study published May 3 in the prestigious Proceedings of the National Academy of Sciences.

Image: MSU graduate student George Rice samples for unusual microorganisms from a geothermal pool in the Crater Hills area of Yellowstone National Park. (G. Rice photo)

The discovery has diverse potential, including aiding the search for life on other planets as well as harnessing useful viral products for medicine and industry.

Scientists George Rice and Mark Young of Montana State University found the virus living among organisms called Archaea (archae means ancient) in Yellowstone's Midway Geyser Basin. Archaea is one of three major domains, or types, of life. The others are bacteria and eukarya, which includes plants, animals and humans.

Many archaea are thermophiles, meaning they thrive in hot, acidic conditions like those in Yellowstone Park and the world's other geothermal areas. And like most living things, archaea have viruses that infect them.

"Anywhere there's life, we expect viruses," said Young, a plant scientist and co director of the Thermal Biology Institute at MSU.

Although scientists expected to find viruses that infiltrate archaea, few have actually been identified. Just 36 viruses have been isolated from archaea out of more than 5,000 known viruses, a fact that makes the Yellowstone discovery a noteworthy one, Young explained.

"This is a stellar example of why we need places that are protected for scientists to come in and look for new discoveries," said park geologist Hank Heasler.

Also unique is the shape of the virus's outer coat, or protein shell, which the scientists found to be similar to a bacterial virus and an animal virus they used for comparison. This similarity suggests that the three viruses have a common ancestor that predates the division of life into its three main forms roughly 3.5 billion years ago.

"Thermophiles are deeply rooted in the tree of life," said Young. "Presumably the viruses are, too."

The research team, which included MSU chemistry professor Trevor Douglas and scientists from the Scripps Research Institute and the Idaho National Engineering Laboratory, also studied the virus's genes. They showed very little similarity to the known genes of other viruses and organisms.

Rice, who graduates this summer with a Ph.D. in microbiology, began hunting for thermophilic viruses in Yellowstone about five years ago. In 2001, he, Young and others reported finding several novel virus and virus-like particles associated with an archaea called Sulfolobus. The pools Rice sampled had temperatures ranging from 158 to 197 degrees Fahrenheit and extreme acidity (pH of 1 to 4.5).

Rice's closer study of one of those viruses led to last week's paper on the ancient structure that seems to span all three domains of life. Now scientists plan additional studies on the virus's genes to figure out what they program the virus to do.

"The genes look different [from those of other viruses] so they probably do different things," Rice said.

Of the world's known viruses, most don't make people sick, but scientists study them anyway for the role they play in evolution, especially in moving genes from one organism to another.

"They're not just a passenger," said Young. "They are the major source of biological material on this planet. They have a huge role in moving genes around."

Heat-loving viruses also serve as models for understanding the biology and chemistry necessary for life at high temperatures on this planet and possibly others.

"If we're going to go to non-Earth-based bodies to look for life, this discovery gives NASA an approach for looking for life in hot-temperature environments, which we know to exist off of Earth," Young said.

The discovery could also yield practical applications, such as genes and other viral products that are stable at high temperatures, an attribute potentially useful in a variety of medical and industrial applications, Young said.

The research was funded by NASA, the National Science Foundation and the National Institutes of Health.

written by Annette Trinity-Stevens and posted for May 11, 2004

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