Comments on: Are viruses alive?

By: Eileen

Eileen — Fri, 27 Mar 2009 19:21:01 +0000

Thank you for your reply about this. I’m just having a little trouble with conceptually understanding one point. It sounds like if a virus is a parasite that it is taking nourishment from a host. How is this different than eating? I suppose one doesn’t necessarily need a mouth to eat. If it’s not “eating,” but merely “attacking” how would that make it any different from a chemical attack? I’m not understanding why it needs a host at all, if it is not alive.

Please help? (sorry to be having such trouble with this concept!)

Eileen

By: ajcann

ajcann — Thu, 26 Mar 2009 08:09:08 +0000

Fair enough. I regard all this as semantic waffle and would prefer not to get dragged into it. However, the question of viruses and “life” is a perennial evergreen and appears on many biology curricula, so it has to be addressed.

By: Richard Badge

Richard Badge — Wed, 25 Mar 2009 21:31:28 +0000

IMHO viruses and people are just complicated ways of making more replicators: given their environment, neither is necessarily more “alive” than the other.

Given the similarities between viruses people (nucleic acid genomes,encoding proteins)surely the debate about what’s alive shouldn’t be staged here… prions anybody?

By: Vincent Racaniello

Vincent Racaniello — Wed, 25 Mar 2009 20:35:35 +0000

Absolutely. Viral capsid, not virus capsid. My colleagues here insist on using virus….but Jane Flint prevailed during the writing of “Principles of Virology”. Can you believe, ASM did not want to use ‘viral’!!!

By: ajcann

ajcann — Wed, 25 Mar 2009 19:11:08 +0000

Yes, it’s a misnomer, in which case, killed virus vaccine is too :-)
Another good one is “growing virus stocks”.
But neither of them bother me, although they are misleading. The one that really gets me is the adjectival usage of the noun “virus” ;-)

By: Vincent Racaniello

Vincent Racaniello — Wed, 25 Mar 2009 19:02:46 +0000

I also believe that viruses are not living. But then what is a spore? Or a plant seed? And what about sperm and eggs – are they living or not? These are some of the many obstacles to my belief that viruses are not living. Remember what André Lwoff said: “a virus is a virus”.

One more thing….why do we use the term ‘live virus vaccine’? I kept saying that while teaching a class yesterday at NYU, and the students laughed, because earlier, I harped on my belief that viruses are not living.

profvrr

By: ajcann

ajcann — Wed, 25 Mar 2009 17:49:30 +0000

Viruses don’t eat or breathe, but they are parasitic on organisms who do. Viruses don’t grow either, any more than a television set or a pencil grows.
If a virus is not alive, what does that make it? It makes it a virus!

By: David Raikow

David Raikow — Wed, 25 Mar 2009 17:26:06 +0000

I consider viruses to be intermediate, not transitional, between organisms and non-living structures. Hence I do not consider them to be alive. They are replicated, but do not self-replicate. Their construction consumes resources, but they do not consume resources. They can persist for extended lengths of time, theoretically forever, but require no expenditure of energy to maintain their structure.

Though their replication is totally depended on cells, viruses remain a facinating example of evolution. They can persist because they are a structure that favors their own replication in an envrionment replete with the mechanism to do so.

I don’t doubt that viruses first appeared shortly after genetic material appeared, and had thus the potential to affect the evolution of life. But they’re likely to only be an accident of the mechanism of genentic replication. I find it hard to beleive that they could be directly part of root origin of life. They would have had to lose self-replicating components without retaining vestiges, and there are none.

That is, unless there was another non-living chemical mechanism of assembling organic structures, from which some viruses evolved an independedt means of self-replication. Then the virsues of today would be descendants of the original “chemical” to “biological” transitional forms. But that’s just a wild speculation.

By: elementaryteacher

elementaryteacher — Wed, 25 Mar 2009 16:45:57 +0000

I would like to simplify this discussion. I teach Grade 3, and we don’t discuss viruses. But as someone very interested in science, I would like to bring it down to the level of a young child. Just by chance, I once saw a Sesame Street episode which was teaching kids how to tell what is alive, and what’s not. They brought it down to three questions.

1) Does it eat?
2) Does it breathe?
3) Does it grow? (or perhaps in this case, reproduce?)

I presume it does eat. I presume it must have some form of respiration. Does it need oxygen? Does it not need oxygen? Do viruses grow once they are created? Or, as you say, if they are assembled like machines, perhaps they do not grow?

If a virus is not alive, what does that make it? A replicating mineral? By necessity, aren’t things either animal, plant, protist, or mineral? If a virus is not a mineral, what category would it properly be called? Or would they be a category completely to themselves?

Eileen