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Comment by zdragnar | Hacker News Reader

In a way, a virus is not too far off from a complex prion. Simple single cell organisms aren't too far off from complex viruses.

There's a line of thought that metabolism is the defining feature of biological life, and viruses do not have any metabolic activity of their own. This is essentially the only real distinguishing characteristic that holds true between viruses and organisms.

Once a virus has a host cell, however, it uses metabolic events to do its thing. That use of those events to drive its own reproduction is very life-like, and is very unlike a prion. In terms of behavior, it really is more like life than not. It uses metabolism, even if it doesn't innately perform glycolysis like everything else.

The "are viruses alive" is really more a medical philosophy question than a practical one.

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In what way is a virus remotely like a prion? Both the structure and function of the parts are completely different.

Just because a virus interacts with a metabolism doesn't mean it's closer to having one of its own. That's like saying humans use gasoline combustion for our biology because we drive cars instead of walking sometimes.

You're not wrong that whether viruses are alive is not a very practical question, but none of the rest of your post meaningfully addresses it either way.

A viral capsid is certainly an evolutionary benefit, but the disease known as "scrapie" astonishingly seems to be able to survive without one for long durations.

We are quite lucky that nothing like that targets humans so effectively.

Yeah, because scrapie doesn't resemble a virus, so it doesn't have the same survival concerns. A protein in an exceptionally low-energy conformation is more robust than a ring of RNA, film at 11.

Anyway, fun fact, the prion that causes scrapie is extremely similar to the ones that cause mad cow disease (transmissible to humans) and Creutzfeldt-Jakob disease (human disease). So yes, we're very, very lucky, so far. Sleep tight.

Actually, the worst cases were from Kuru.

It has a ghastly origin.

https://en.m.wikipedia.org/wiki/Kuru_(disease)

(I will upvote you now.)

Sure, but Kuru doesn't transmit anywhere near as easily as scrapie does in sheep, which seemed to be the relevant comparison.

>That's like saying humans use gasoline combustion for our biology because we drive cars instead of walking sometimes.

I imagine you are speaking more in terms of molecular biology, but if we zoom out into evolutionary biology this is not such an unreasonable statement if we are talking in terms of the extended phenotype.

Especially as we get closer to a robust hypothesis that humans lack free will on a biochemical level, it really could be that our genes making use of gasoline, because the "we" that we like to think of as making use of it through intellect and choice is more a hallucination (perhaps useful in some way, perhaps mere side effect) than a biological reality.

Humans using petroleum isn't necessarily all that different from how a parasite modifies host behavior as an essential part of its lifecycle, or how a beaver builds a dam to have a much more survivable environment.

And then on the other side of prions, you get things like asking whether self-catalyzing crystal formations are alive.

I like to think of a virus like code. It’s nothing more than a series of instructions in a file that, when executed (by the cell), does something. Is code complex enough to be called life?

We call self replicating programs viruses when they're unpleasant and quine as curiosities.

Is the game of life, life?

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