News release, October 30, 1998, effective immediately.
For media inquiries, contact Caroline Booth Lara, Communications Specialist, (580) 224-6379.
  email: cblara@noble.org

(Sidebar for Marilyn Roossinck's award article)

What is a biodiversity inventory of viruses?

by Marilyn J. Roossinck, Ph.D.

Associate Staff Scientist, The Noble Foundation

Most of us are familiar with viruses that make us sick, like the rhinoviruses, which cause the common cold, or influenza virus, which causes the flu. Some farmers and ranchers may also know about viruses like tomato spotted wilt virus or cucumber mosaic virus that can make plants sick. Viruses can infect every known type of organism, from bacteria to humans. Some of them, especially plant viruses, can also remain in a dormant state outside of a host for long periods of time. However, almost nothing is known about viruses that exist in most of the natural world, the world outside of humans and their crop plants and domesticated animals.

Viruses are the smallest known life forms. Some scientists don't even consider them alive. Many of them have only three or four genes, while others like the poxviruses (the virus that caused small pox is in this group) have more than a hundred genes. The genes are made up of RNA or DNA, and each gene carries the blueprint for a viral protein. Viruses are always parasites; that means that they can only live and grow inside the cell of another living organism. They use the host cell to make the proteins that are encoded by their genes. The proteins are used as enzymes (biological molecules that catalyze a chemical reaction) or as a coating for the viral genes, to allow them to pass to a new host.

Most viruses we know about disturb the host cells when they infect them, making people and plants and animals sick. Many people think all viruses cause disease, but this is only because no one has ever studied the viruses that don't cause disease. But everyone probably has plenty of viruses living inside them that don't cause any disease. Many years ago when scientists first starting using monkey cells grown in culture for medical research, they found more than 50 viruses in these cells, but only one was ever studied because it was found to cause tumors. The rest had no apparent effect on anything. About 250 different viruses have been described that infect humans, most of which cause disease. If the same ratio is true in humans as in monkeys, there would be more than 12,000 viruses that infect humans without causing disease.

Why is it important to know about viruses that don't cause disease? One important reason to know is because viruses that don't cause disease in one organism (perhaps their natural host) can occasionally jump into a new host species and cause severe disease. This is what happened with HIV, the virus that causes AIDS. HIV was originally a monkey virus. It didn't cause any disease in monkeys, but it has been devastating in humans. There are many other examples of "emerging" viruses, in both plants and animals. Since we don't know anything about natural or "wild" viruses, we don't have any tools to deal with emerging viruses quickly.

Another reason is to understand the role that viruses play in a natural ecosystem. They can actually be a benefit to their hosts. Sometimes infection with a virus that doesn't cause disease will prevent infection of a virus that does cause disease. Sometimes viruses are important in helping an organism reproduce. Viruses may also be important in controlling populations in a balanced ecosystem.

Finally, a lot of what we know today about molecular biology came from studying viruses, and viral enzymes have become very important tools for biomedical research. Newly discovered viruses may offer a lot of new information and new tools for research and medicine.

The problem is that we don't know very much about viruses because we have only studied a very small fraction of them. A biodiversity inventory of viruses will take a defined region and survey every life form in that region — plants, animals, insects, fungi, bacteria, etc. — for viruses. There are two regions where virus inventories are being organized: the northwestern region of Costa Rica, and the Great Smokey Mountain National Park. An inventory is an enormous task. It will take a lot of scientists a long time to complete them, but even completing a small part of the inventories will tell us a lot more than we know now about the unseen world of viruses that surrounds us and is within us.

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Noble Foundation Scientist Wins Award

(FYI — The Noble Foundation is a privately funded, nonprofit organization headquartered in Ardmore, Okla. The Foundation conducts agricultural and plant biology research; provides grants to numerous other charitable and educational organizations; and assists farmers and ranchers through educational and consultative programs.)