Viruses Infected By Viruses

SpaceAdmiral writes "Scientists have discovered a virus that can infect another virus. The fact that viruses can essentially get sick may change the debate over whether they are alive or not. Check out Nature for a slightly more technical article about the 'virophage.'"

Comments

Re:reproduction

[evolvearth]

That's pretty much why viruses aren't considered alive, as they only propagate by hijacking living organisms' replication machinery. Eunuchs are individuals, that the definition of life applies to species, not individuals. Mules can occasionally reproduce, but is rare and it's due to the unequal distribution of chromosomes in meiosis. This isn't why they would be consider alive, they are the offspring of organisms that are alive. It's just an anomaly of nature. All viruses are parasites that depend on a host's replicating machinery by definition, therefore cannot be considered living.

not alive

[rritterson]

No, they are not alive even if they can get sick. Viruses, even infected ones, cannot self-replicate as they require the use of a host and host machinery. If you can find me a self-templating virus, then we'd have an interesting discussion...

viruses infecting viruses is still cool though.

Re:cancer

[SpottedKuh]

Didn't you hear?, everything is linked to cancer or at least if you listen to the news thats what it seems like.

There was a very interesting editorial piece in my local newspaper today on pretty much this topic that deserves to be read by anyone working in health / safety / threat / etc. research.

The short point is that when every preliminary study, or even hypothesis, is presented by the news media in the same fashion as something that has stood up to rigourous testing (e.g., smoking causes cancer), people begin to filter out everything.

That being said, my short summary doesn't do the editorial piece justice.

there's no easy answer

[QuantumG]

Is a mule alive? It can't reproduce. Maybe you object because the mule is *made* of cells, each of which can reproduce, but your body is full of cells that can't reproduce, are they alive? What's reproduction got to do with being alive anyway? If you take a cell that can reproduce and mutate the gene that produces a necessary protein for the reproductive process, is the cell now dead? It can still metabolize, make other proteins and interact with its environment. When it no longer can, that's when we say it is dead. As such "living" already has a good definition, even if it isn't too strict, and that is the opposite of dead or, more precisely, "inert". Viruses are not just a package of DNA, (or RNA), they're also a system of proteins for delivering that package from cell to cell. A virus most definitely isn't "inert" in the same sense that a "dead" thing is. So if something isn't dead, what is it? Undead? We typically reserve that word for horror writers, and just say "alive".

I think the objectionable aspect of calling viruses "alive" comes from people thinking of viruses as "pure information", they're not. They're complex machines that can cause their own replication in their environment. Their environment just happens to be living cells, which are also complex machines that can cause their own replication in their environment.. To accept that a virus isn't alive because it needs its environment means you have to accept that a cell that requires a water environment isn't alive, or all multi-cellular organisms are not alive. Are mitochondria alive? Are the cells that require mitochondria alive? How about yeast? How about that mule?

Re:there's no easy answer

[rritterson]

Parent is probably the most detailed response to my original post, so I'll address it, even though the chances (several hours after the article hit the front page) of someone reading or modding it are virtually nil.

Comparing a virus to a mule is a false comparison. With objections to those who seek a single, simply, unified definition, the standards for a living mammal simply do not compare to those of a single celled organism, let alone a virus. The simple fact that a mule cannot reproduce does not negate the fact that it has virtually all of the reproductive machinery and virtually all of the capacity to reproduce, plus a few defects (and, in fact, some mules can reproduce). No virus is prevented from independent reproduction due to a simple defect or mutation.

Saying that a virus 'lives' within a cell is a subtle argument that has merit. I find it lacking, though. To explain why requires an extension of my original argument: A virus, while able to harness the energy sources around it, does not have the enzymatic capacity to transmute energy sources into the ones it needs to survive and replicate. In addition, a virus is unable to respond to changing conditions around it, such as increased heat, a modified energy source, etc. Within the 'lifespan' (using the term loosely), a virus invades and replicates, period. Our cells can respond to various signaling components, change metabolism based on condition, and reproduce when asked. A virus simply cannot.

Mitochondria are not alive, because they cannot survive outside the confines of the cell, let alone replicate. Is your heart alive? By the very same token, yeast are indeed alive. Mules are alive, though reproductively deficient. Following the same idea, and borrowing your definition, a robot that could create another copy of itself would be considered alive in the 'environment' of the factory where it was built.

Re:reproduction

[conlaw]

What about computer viruses and worms?

TaDa! This just in from Science Daily:

Alaa Abi-Haidar and Luis Rocha from the Department of Informatics, Indiana University, Bloomington, USA and the Instituto Gulbenkian de Ciencia, Portugal, will present a paper entitled Adaptive Spam Detection Inspired by the Immune System on Thursday 7 August. They will describe how in the same way as the vertebrate adaptive immune system learns to distinguish harmless from harmful substances, these principles can be applied to spam detection.

http://www.sciencedaily.com/releases/2008/08/080806194601.htm

Re:here we go again

[Anonymous Coward]

It would seem to me that there is some significant qualitative difference between humans and rocks. Extending that further, it seems there exists differences between bacteria and rocks.

Essentially, the question is what is the largest subset of differences that can be used to distinguish between something that is alive and something that has never been alive.

A question arising from the previous one is, what is it exactly that separates life from death. We can't even detect life - only the by-products of what we define as life. Thus we define death as the absence of those by-products of something that at one point had displayed those by-products.

So I would disagree that the question is flawed. I think it might be oversimplified sometimes, but that at its core, it captures a very fundamental set of questions which essentially, arise from, "What does it mean to be human?" and "What is intelligence?"