Creative Commons Xiao et al., Public Library of Science. Click image for link.
I’ve got a new post up at the Scientific American Guest Blog: “Pimp My Virus: Ocean Edition” about the fascinating and newly discovered world of giant viruses. You haven’t seen viruses like this before. Hope you enjoy!
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Jennifer,
just read your great article in the SciAm blog.
It brought an idea to my mind which I had some time ago. Maybe, the following is nonsense, maybe it isn’t:
I wondered if the question “are viruses lifeforms or not?” is simply the false question.
Most viruses are not actively invading their host cells, the host cells pick them up.
Some host cells may be predators, so they cannot stop doing that without starving. But the majority of cells are no predators. Why do they pick up viruses?
Maybe, the virus is originally not something “intended” to make sick, but to transport RNA or DNA.
Maybe, the majority of viruses does not carry a disease but something of value, and the benefit of obtaining that is higher for a cell than the risk of catching a disease?
Are viruses originally a vehicle to transport genes that potentially increase evolutionary fitness? Are they essential for survival under changing conditions?
Are they instead of lifeforms more a kind of book titled “The Genetic Handbook of Self-medication – How to Protect Yourself from Antibiotics and other Nasty Stuff.” or so
Why would an organism create such an essential virus? Because most other organisms of its species around may be somewhat related with the source organism. Would increase the survival of the kin, not only the individual itself. And this kin has DNA coded for essential virus production, the DNA segments would therefore increase the evolutionary fitness of its owners.
I ended my thought with: So, if there are “essential viruses”, why has no one seen them yet? Possibly because no one has searched for them yet? Highly unlikely.
After your article, my immediate reaction was: Hey, this is no more unlikely at all. No one has ever searched earnestly for essential viruses. I may have been right.
fascinating! especially mamavirus and sputnik. definitions expand!
Hi Oliver,
That is indeed a pretty crazy idea! It’s not impossible, though, but seems unlikely given the costs to fitness that being sick with many viruses entails. I have a cold right now, and even such a mild virus as rhinovirus is making me pretty unhappy. Think of the cost to the host of much more serious viruses like HIV, Ebola, Hantavirus, Rabies, etc. Still, with some viruses like West Nile virus, the majority of people who get it don’t get sick at all — only a very few do. Could the people not getting sick be gaining some advantage? Probably not. And here’s why I think that: we’ve read the genomes of almost all these small viruses. We know what all the proteins are. And all the proteins seem to be needed by the virus in some way — for making a coat protein, or a replicating enzyme, etc. And though viruses can be passively picked up, some actively exploit cell chemistry to sneak in by exploiting cell transporter systems. They definitely want (as much as you can say a virus “wants” anything) to get inside the cell. But even in a giant virus like mimivirus with plenty of room for extra genes that could be beneficial to the host, the virus still has costs to its host in terms of decreased fitness that probably outweigh any benefit they could receive. Plus, as Richard Dawkins points out in “The Selfish Gene”, the unit of selection is the virus — not its host. Evolution will select for viruses that are most effective at producing more successful viruses — and nothing more.
Still, it’s a very interesting idea! And here’s one way you may be right: the virus version of “heaven” is achieving immortality (and guaranteed reproduction) by permanently integrating itself into its host’s cell line. And it looks like that’s happened countless times, as scientists are finding hundreds of fossil virus sequences in human DNA. It’s possible some of that fossil virus DNA could get co-opted and repurposed by the host for some new function that is beneficial. Scientists may have even already found examples of this — does anyone know?
And yes, kati — love Sputnik and the mamavirus. Sounds like it could be a great name for a band . . . : )
michael pollan writes about how corn has evolved to practically *need* human help to reproduce so in a way, corn has masterfully found a way to make us it’s bitch :) i guess that’s one way to look at it, another way to look at it is that it’s sadly developed a system that is unsustainable as it is on it’s own. thinking about viruses, and especially oliver’s comment for some reason, makes me think of corn…
aren’t we experimenting with using virus “shells” with their harmful “guts” replaced with more beneficial “guts” to cure diseases? not to mention aren’t some vaccines made with live viruses? for some reason it makes me wonder if those viruses are somehow learning to make us their bitch, just like corn, and at the same time becoming essential instead of harmful. hmmmmmmm. :)