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Published online 6 August 2008 | Nature 454, 677 (2008) | doi:10.1038/454677a
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'Virophage' suggests viruses are alive
Evidence of illness enhances case for life.
The discovery of a giant virus that falls ill through infection by another virus1 is fuelling the debate about whether viruses are alive.
“There’s no doubt this is a living organism,” says Jean-Michel Claverie, a virologist at the the CNRS UPR laboratories in Marseilles, part of France’s basic-research agency.
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Where are the prior comments?
good question..
Big fleas have little fleas upon their back to bite 'em. And little fleas have smaller fleas, and so ad infinitum! The issue about viruses is whether the use of external metabolic processes invalidates their claim to life. But in similar way, animal dependance on vegetable life for their metabolic processes could similarly be argued to invalidate our claim to being alive. The issue about life has a cause in that we assume life to be inherent in an agent, rather than in the total of an agent and environment. Clearly the entire system of mini-virus, maxi-virus and host is alive. Trying to partition the system into alive and non-alive components does not work.
A lot depends on how you define "life". If you define it as a membrane-bound self-reproducing system controlled by genes, then a virus indeed fails to be "alive" through its failure to be membrane-bound. However, I feel that this type of definition assumes attributes that most likely themselves arose through evolution from simpler systems. My own view is that "life" is any self-reporducing chemical system. In that case, viruses very much are alive because they do reproduce themselves in an appropriate environment.
Apart from self reproduction,processing of intelligence in a systemic specific manner for survival and functional success is what essentially characterizes life.More over a microlevel concept of life is very partitioned and narrowly defined since it does not account for the multilevel and meso as well as macroscopic feedback mechanisms that promote coexistence while allowing room for competition,in a purposive manner with a system oriented functional approach rather than a reductionist one. thanks SURESHKUMAR.S,SCIENTIST AND ADVISOR,POLICY,NIIST,TRIVANRUM
"Intelligence" seems me to be an anthophromorphing of the idea of "life". I hardly see a bacterium as posessing any intelligence or even thought, and yet it has a highly systematic means of maintaining and perpertuating itself. I return to my initial point: That all such systematic means must themselves have arisen through evolution from simpler systems: Those systems that worked were of course the ones that sucessfully perpetuated themselves, and which were built on to create the complex forms seen today.
In the Acidianus two-tailed virus case, it's showing that virus can independent development without host cell. How to define "alive" or "non-alive", "growth" or "just protein rearrange"?
The standard definitions of viruses cover the combination of "mamavirus" and "Sputnik" (aaaaarrrrrgh!!) quite adequately. The mini/mamaviruses are viruses, however big their genomes, because they are obligate intracellular parasites which require host cell machinery (read: ribosomes) in order to replicate - and make a pool of components which assemble to make particles to spread the virus around. The very badly-named "Sputnik" is simply a satellite virus - albeit one with a large genome - because it apparently requires the presence of another virus to replicate. As for "stretching the boundaries of life" and other guff: this has been dealt with adequately in these responses; I will confine myself to saying that "life is the phenomenon associated with the replication of self-coding informational systems". And these are certainly those....