August 15, 2008

Giant virus gets infected by other virus, might be alive... then again, it might just not

ResearchBlogging.orgThe scientific blogosphere is all a-twitter about a recent report and advance publication in Nature describing how giant mamaviruses, amazingly and surprisingly can, using extremely simplified terms,"get infected" by other much smaller viruses. You can read more accurate accounts here, here, here or here.

This discovery is without precedent and undoubtedly really cool and interesting; but something irks me. In the original Nature News report one of the scientists behind the discovery has this to say:

There’s no doubt this is a living organism. The fact that it can get sick makes it more alive.

The more I think about it, the less can I make sense of the words "more alive" and all the ramifications it evokes. But that aside, there's a very heavy emphasis on whether or not this qualifies giant viruses as being alive, and most of the reports that followed have simply repeated this perspective.

This irks me because it leaves you with the idea that there is a satisfactory all-encompassing definition of what life is. There isn't. What there is is a bunch of different suggestions that manage to either describe some "common denominator" processes carried out by living organisms or capture a sort of approximation of what it is that we experience as living, but that all leave something out.

Why does this seem to bother us so?

I have always found the question of the "definition of life" to be a capricious and fanciful one to ask. Not because the answer eludes us, which it does, but because it often only seems worth asking precisely because it's capricious and fanciful. What would we actually gain from pin-pointing the answer? What would it add to our knowledge? I'm open to the though that there is in fact no answer and I tend to think that we're actually asking the wrong question. Whether or not something is living (or whether it's more or less living than something else...hahaha) is never more interesting, or more important, than the facts that underlie the claim. I agree with Carl Zimmer's suggestion:

I think it's better to think about life not in terms of hard definitions, but in terms of rules--ways in which species tend to work, no matter how different they seem superficially.

It's far more rewarding to focus on how this discovery enriches our knowledge of the relationships between viruses and their hosts and how it might broaden our view of the processes that organisms are able to carry out. In that sense I definitely want to include viruses among the rest of living beings. But discussions about what the nature of life really is tend to get a bit lofty and usually lead us nowhere. Claiming that this latest discovery questions whatever definitions we might have of life is definitely taking it one step too far.

Bernard La Scola, Christelle Desnues, Isabelle Pagnier, Catherine Robert, Lina Barrassi, Ghislain Fournous, Michèle Merchat, Marie Suzan-Monti, Patrick Forterre, Eugene Koonin, Didier Raoult (2008). The virophage as a unique parasite of the giant mimivirus Nature, 455 (7209), 100-104 DOI: 10.1038/nature07218

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