Monday, November 12, 2007

Just how wrong is Marilyn vos Savant?

Marilyn vos Savant is a writer of a regular column in Parade magazine. These columns address many things, but often have interesting logic puzzles. Given that she is claimed to have the highest recorded IQ ever, whole sites have sprung up to find fault with her writings. Now, I'll confess I'm always looking for an angle -- and rarely finding one.

But this past Sunday, she gave me a bit of an opening: in response to a question as to whether there are any beneficial viruses. Her response:
No. Bacteria are living one-celled microorganisms. By contrast, viruses aren’t alive in a strict sense: They are the ultimate parasites and cannot replicate without a host. They invade the cells of animals, plants and even bacteria, then either lie dormant or get into the driver’s seat and cause changes that disrupt normal cell functioning, the very essence of disease.

The first two sentences and most of the third are dead on the money: bacteria are unicellular organisms, viruses aren't considered alive & invade other cells, where they can lie dormant or immediately go crazy. However, that last bit is the clincher. Apparently Ms. vos Savant is unaware that in the bacterial world there are examples of viruses benefiting their host by bringing along useful genetic stuff. Diptheria is one example, in which the toxin (which presumably helps the bacterial host) is encoded by a virus (phage).

Are there examples outside of bacteria? I don't know of any, but I'm hardly up on my viruses. Moreover, how would we know? Suppose there were viruses which were simply neutral (or nearly so), would we have ever detected them?

Also, in a broader sense some of those phage out there may be an important ecological control on bacterial nasties. So this could be another class of "beneficial" viruses.

Just because you are a parasite doesn't mean you're guaranteed bad!


Anonymous said...

not sure about replication of this results, but there was an article stating that mice are protected from some bacterial infections by latent herpesviruses
also yersinia pestis virulence was associated with a phage

Unknown said...

Not sure about wild-type viruses, but we use viral vectors quite a bit to deliver drugs.

Anonymous said...

I would have though the most famous example is cowpox, which immunises against smallpox.

such.ire said...

I remember reading somewhere about a virus that's integrated into the wasp genome and active only in the gonads. When the wasp injects a caterpillar with eggs, the virus activates and disables the caterpiller's immune system to help the wasp larvae survive.

Anonymous said...

My dissertation research was on bacteria which form symbioses with soybean plants to fix nitrogen. The line between symbiosis and parasitism is pretty fine. It's symbiosis if it's useful, and parasitism if it's harmful. Symbiosis may even be an evolved form of parasitism. A parasite which kills its host too quickly (like ebola) may be limited in growth and spread due to the inability to find new hosts. A virus/bacteria which benefits its host (thereby being a symbiont, rather than a parasite), can grow and spread far more freely.

GaryM said...

Given that all living organisms appear to have viruses associated with their populations, it is possible that viruses play a necessary role in the evolution of all life on earth, perhaps through lateral gene transfer up the evolutionary ladder. Nothing grows faster, is more fecund, nor mutates at a higher rate than the populations of microorganisms on our planet. In our very bodies we carry ten fold more bacterial cells than eukaryotic cells. Imagine the vast levels of mutation occurring within these populations. Perhaps viruses serve as important vectors in the exchange of selected genetic information between species. I also wonder if like matter itself, which seems to be an artifact of an otherwise perfect universe, the key role of viruses is to replicate on occasion imperfectly, thereby gaining new genetic information and passing it along within related species and so on up the ladder. If it is true that mutations are mistakes, then perhaps all of evolution, including our viral partners, exist because mistakes are necessary for evolution and life.

Anonymous said...

Science 26 January 2007:
Vol. 315. no. 5811, pp. 513 - 515

A Virus in a Fungus in a Plant: Three-Way Symbiosis Required for Thermal Tolerance
Luis M. Márquez,1 Regina S. Redman,2,3 Russell J. Rodriguez,2,4 Marilyn J. Roossinck1*
A mutualistic association between a fungal endophyte and a tropical panic grass allows both organisms to grow at high soil temperatures. We characterized a virus from this fungus that is involved in the mutualistic interaction. Fungal isolates cured of the virus are unable to confer heat tolerance, but heat tolerance is restored after the virus is reintroduced. The virus-infected fungus confers heat tolerance not only to its native monocot host but also to a eudicot host, which suggests that the underlying mechanism involves pathways conserved between these two groups of plants.

Anonymous said...

Heh! Having read the same vos Savant item, I googled around and found this.

Parasitoid wasps inject virus-like particles into caterpillars when they deposit their eggs. The VLPs are essential for destroying the caterpillar's immune system, so the eggs can develop without being destroyed themselves.

Assuming these are true viruses (some people think not), they are clearly beneficial for the wasp.

For the caterpillar, not so much.

Anonymous said...

It has also been postulated that the origin of the eukaryotic nucleus is viral. Evidence includes nuclear membrane structure and the fact that eukaryotic chromosomes are linear like viral genetic material as opposed to circular.

Silas said...

Reading that answer in context, I think that "beneficial—even vital—to human health" is presumed throughout the answer. That said, even if her conclusion is correct, her logic makes no sense.

Anonymous said...

the very word "beneficial" is an anthropic judgement. Our understanding of the meta genome or functioning of higher level systems dynamics over time is so poor as to make a "beneficial" label pretty pointless as it is a narrow anthropic analysis. One could pose the equally preposterous question, which plants and animals are beneficial?