Viruses - The New Ancestors of Life

It may be frustrating, but it happens to the best of us: an excruciating headache, an upset stomach, and even a common cold, among many other conditions that would truly characterize you as ill. You can get over the illness, but it is cumbersome while you have it. More irritating than the pain is the fact that there is no clear scapegoat.

Medieval pathologists theorized that evil spirits caused sickness, but as a result of the French chemist Louis Pasteur's germ theory, it is agreed that diseases are caused by small microorganisms, invisible to the naked eye. The germ theory has developed since its formulation, and modern scientists know that many illnesses frequently result from something that in Latin means slime or poison and today means something that slows down your computer - a virus.

Viruses, as you probably know, were and continue to be responsible for some of history's deadliest and most devastating outbreaks and diseases. Yet, for decades, scientists debate whether this inimical creature is even alive. However, in 2003, the bacteriologists Bernard La Scola of the Rickettsia unit of Mediterranean University in Marseilles, France recently discovered the most complex virus yet, the Mimivirus. The structure of the virus not only suggests that viruses are living, but that the virus, the supposed arch-enemy of life itself, is the first living creature.

The virus was first discovered by the Russian scientist Dmitry J. Ivanovsky in 1892; when investigating diseased tobacco plants, he identified what would be the tobacco mosaic virus. In 1898, the Dutch scientist Martinus W. Beijerinck used porcelain to filter the juice from blighted tobacco leaves, even removing all the bacteria, but the juice remained pathogenic.

Beijerinck, unlike Ivanovsky, realized that the virus was an organism unlike any other and was distinguishable even from bacteria. Only by 1935 were scientists able to see the mosaic virus, using an electron microscope. In 1946, the biochemist Wendell M. Stanley received the Nobel Prize in chemistry for his crystallizing and purifying viruses to determine their structure. That he received the reward for chemistry, not biology, shows how people did not view viruses as living organisms.

Nevertheless, a virus does have structures that are similar to those of other life forms. It is composed of nucleic acids, either deoxyribonucleic acid or ribonucleic acid, and proteins, some of which form a capsid that covers the virus. The virus uses its host's cells to replicate itself and perform its metabolic functions. Scientists believe that viruses formed from cells' nucleic acids at some point in the evolutionary stage but that they could not have survived without any cells to live off of. However, the multitudinousness of viruses has raised questions on this theory.

Currently, researchers can characterize around 4,000 different viruses from dozens of families, but that is only a minute fraction of the number of viruses on Earth. With the recent discovery of the Mimi, scientists are rethinking the virus's role in evolutionary history.

The Mimi's recorded history starts in 1992, when there was a pneumonia epidemic in Bradford, England in the county of West Yorkshire. Britain's Public Health Laboratory Service's Timothy Rowbotham discovered an amoeba near the town's cooling tower and realized that the amoeba attracted Legionella, a virus first identified after it caused a pneumonia epidemic in 1976 at the American Legion convention in Philadelphia. Rowbotham collected a number of samples from the amoeba, including what would be the Mimi.

La Scola, at the time he discovered the Mimi, was examining a sample of Legionella, and happened upon a viral-shaped creature that was far larger than any normal virus. Jean-Michel Claverie, a bioinformatics specialist at the Institute of Structural Biology and Microbiology in Marseilles, compared the genes of the Mimi with that of various eukaryotes, bacteria, and archaea. From the comparison he deduced that the Mimi is part of an ancient line of DNA viruses.

Scientists concluded that the Mimi, early in its evolutionary stage, shed some of its genome and ability to replicate itself. Since the Mimi's discovery, scientists have discovered many other ancient viruses with unique genes.

In a recent conference of microbiologists, cell biologists, and evolutionary biologists held in Les Treilles, France titled "The Origin of the Nucleus", scientists, in light of the recent discoveries, suggested that viruses could be the ancestors of all living beings. Life originated with a mixture of slimy, liquid, single-celled bacteria and archaea. A virus related to the Mimi might have attached itself to an archaean or bacterium and help form a nucleus, a feature of all eukaryotic cells. Part of the proof for this is that the Mimi and the eukaryotic cell nucleus replicate in similar ways. The scientist also pointed out that because the virus replicates frequently, its genes are likely to have mutations, enabling the virus to adapt to its environment and evolve. This discovery might possibly revolutionize the way scientists view the world's most peculiar creature. Despite the recent discovery of the Mimi and its awesome powers, one still cannot make bad stereotypes about viruses just because a small portion of them are dangerous.

Scientists know that there are innumerable viruses, the overwhelming majority of them yet to be discovered, existing anywhere in the world, even inside us. In fact, it was the very myriad of viruses that helped bring about the discovery. So when you inevitably hear about the newest virus scare, you can at least take solace in the fact that the virus is the basis of all existence and a complex creature that we have still have much to learn about.