Friday, January 14, 2005

Viruses: Parasitic or Symbiotic?

I was reading this article in Scientific American "Are Viruses alive?" and there were some interesting points. Once again I wish I could link you to a version of the article to read for free, but once again you have to pay for it because science needs to be purchased not shared. Ironically if you want a business magazine about science and technology like Wired then the knowledge is freely shared but if it is a pure Science magazine then you need to pay.

The question about whether viruses are alive comes down to a lot of semantics. They can't replicate on their own, they need another being's cells in order to do that. But they share a lot of other traits that we associate with living. Whether you consider them alive really just depends on your definition of alive.

That is not what intrigued me about the article. What intrigued me was the fact that viruses can integrate their DNA into the hosts DNA. Now sometimes that isn't a good thing like the HIV retrovirus, but there is no reason why viruses couldn't also spread good genes.

This article calls virus the world's leading source of genetic innovation because there are so many of them and they mutate so quickly. They constantly "invent" new genes. It is possible for viruses to "take" genes from the hosts they are in. It is also possible for a virus to switch between species. So it is conceivable that a gene from a pig could be transferred to humans via viruses. Or that a gene the virus invented itself is transferred to humans.

With bacteria there are many common species that live in our bodies in a symbiotic fashion, helping us to digest food and other good things. Before this article I had never thought of a symbiotic virus. But know I find it hard to conceive that there are not such viruses. This article states that most known viruses are innocuous, not pathogenic. They take advantage of the cells apparatus to reproduce at a slow and steady rate.

Which makes me wonder how many viral particles are "living" inside my body right now? It is estimated that there are 10^30 viral particles in the oceans either within cellular hosts or floating free. That sounds like a big number to me.

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