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Nymaz t1_jbovj2r wrote

Reply to comment by Jale89 in I just learned that the known shortest DNA in an “organism” is about 1700 base pairs in a certain virus. Is there a minimum amount of “code” required for an organism (or virus) to function in any capacity? by mcbergstedt

> doesn't really represent an organism because it requires the mechanisms of a cell to replicate.

Is there a specific definition of "organism" that includes this requirement? Not trying to be snarky I'm genuinely curious. I always thought that "organism" just meant a unit of "life" which just requires the ability to reproduce, and doesn't include the mechanism.

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Nietzschemouse t1_jbowwcd wrote

Eh. Not really any more than there is a concrete definition of "species".

Lots of biologists don't refer to viruses as organisms, but there's a fair argument that they're no less alive than any other parasite.

I'd say, noting this is tangential to my field of study, that the (EDIT: agreed upon) minimum requirement is a cell membrane. Viruses may have capsules, but it's not quite the same. I believe this to be unnecessarily arbitrary, but it's consistent with keeping viruses out of the alive category

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InfamousAmerican t1_jbp0ugv wrote

Would replication of RNA/DNA not be sufficient to be considered an organism?

I see why the parasite/virus case is similar. Does the difference stem from the necessity of a host for viral replication?

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ayelold t1_jbp4m0g wrote

Viruses don't have a metabolism. Generally speaking, using energy is part of being alive. Also, a virus doesn't replicate its own DNA. It co-opts the replication mechanisms of a host cell and forces the cell to do the replication.

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rickdeckard8 t1_jbp714o wrote

There are no easy dividers like these to separate life from non-life. The short answer is that it depends on how you define life. Others define it in another way and include viruses among live organisms. Just like there is no clear definition on what a game is.

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Nietzschemouse t1_jbp3fdp wrote

In my opinion, that's enough, but the taxonomists of the world disagree.

There are so many organisms that are obligated to have a host to survive. Granted, they mostly need one condition or another that the host provides, rather than invading its cells, but I much find the distinction between virus and obligate pathogen to be just one that is being held onto rather than one that is meaningful. I'm open to someone giving me a real definition, though I've never encountered one I feel satisfying.

Worth noting, my opinion on the lack of consensus for species is that there genuinely can't be one. Humans try to classify biology, but biology doesn't care. You can look at the clostridium or clostridioides clades or the bacillus cereus groups and see examples of biology laughing at us trying to name a species when there is so much intermingling and genetic transfer or so little genetic difference between "species". Dengue virus subtypes might be even clearer, though that's an example of what should arguably be four species being lumped into a single one. Also, why would a non living entity be granted living entity taxonomy like "species" or "genius"? I think that's a matter of convenience, but it does raise an eyebrow because viruses have evolutionary histories as rich as bacteria or animals.

Then there's the "there's no such thing as a tree" argument, that I personally subscribe to.

Long story short, between understood "convention", attempts at classification (taxonomy) that can only approach but never reach the truth, the complicated phylogenetic nature of the world - the fuzzy line between the same and different, and the general resistance to change, I don't think there's really a clear answer for what constitutes an organism and why. Again, I'm open for debate or education.

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CreaturesLieHere t1_jbq7yb9 wrote

I think the answer lies in quantum physics, we may find some mechanism there that exists in typical life but doesn't exist in atypical thing like viruses and self-replicating RNA. Either that, or it lies in chemistry and we just haven't found the right experiment to make the discovery with. Because the line between "a mix of compounds/elements that can do complex things" and "life" has to be drawn somewhere right?

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TheNorthComesWithMe t1_jbqhi7s wrote

There doesn't have to be any fundamental measurable difference between something that is or is not life. Reality doesn't really care about our need to define things.

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Elladan71 t1_jbrmf6j wrote

This is undeniable. But when we're talking about definitions, aren't we talking about human constructs, attempts to approximate truth? Isn't it the same impulse that birthed the scientific method? Drawing lines between things is *useful!

Plus, anything that provides conversation like this thread is worth talking about, if you ask me.

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CreaturesLieHere t1_jbqo3rx wrote

There are several measurable differences between cells and viruses.

Defining what viruses are, and thus whether or not they're considered "life", is quite scientifically important. We need to define things based on what their uses and limitations are. Viruses are already known to have unique characteristics; if we further define those characteristics and are able to distinguish them from organisms, we can potentially discover new things about life, or new things about almost-life as a whole that fits certain parameters. We dont know what we don't know. Everyone freaking out over labels is missing the point, as usual.

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Nietzschemouse t1_jbq98ao wrote

I mean, sure. Maybe such a thing exists, but if we don't know of that, we're just making things up.

Not that it matters, but I don't personally draw a line between a bunch of molecules and an animal. Granted, that's not a common opinion

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blacksheep998 t1_jbp6ca6 wrote

There exist self-replicating strands of RNA. All they are is RNA in solution that can gather and assemble loose nucleotides into copies of itself.

But if a virus is alive, then they could probably be considered alive too.

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omgu8mynewt t1_jbphzq3 wrote

I work with viruses, some virologist like 'genetic material replicating and closed in a membrane' which makes me laugh

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dave-the-scientist t1_jboxhrl wrote

It really depends who you ask. Some consider viruses to be alive, others do not.

True, a virus can't function unless it's inside a cell with access to those nutrients/cofactors, and existing proteins and other components. But a bacteria also can't function unless it's in an environment with appropriate nutrients/cofactors and existing proteins and other components. The only difference is that those proteins etc already exist when the bacteria is born (divides into daughter cells), while a virus has to go and find them. Does that difference define life?

But then, if you consider a virus to be alive, what about self-replicating plasmids? They're really not much different from a virus. What about transposable elements in a genome? Are they alive too? They're not much different than a virus in latent phase.

The definition of life is something that sounds like it should be easy, and high school textbooks do give a precise definition. But the reality is a lot more complicated and murky than it seems.

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Dachannien t1_jbozrot wrote

For that matter, what about a prion? Does nothing when not in the presence of similar amino acid chains that are in a vulnerable conformation, but makes more of itself when those resources are available.

Then again, prions don't breathe and eat and grow, and that is how we know they're not alive.

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dave-the-scientist t1_jbpdrcx wrote

Right? The concept of "life" is surprisingly tricky. But I personally would not consider prions to be alive.

I will say though, prions definitely "eat", when they destroy the normal form of the protein. They "grow" by increasing their population, much like bacteria / viruses. Breathing is not a requirement for life.

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mdielmann t1_jbq3wst wrote

By these definitions for eat and grow, a fire is alive. I'd consider prions no more alive than fire, while still being as dangerous as fire.

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dave-the-scientist t1_jbq760p wrote

Behold, a man!

But yes, examples like fire (nice idea on that one btw) are why "life" is weirdly tricky to define.

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mdielmann t1_jbq8clj wrote

I get the edges are very blurry when defining what something is or isn't in biology, but I wouldn't equate destroy or alter with consume, or grow with reproduce, either.

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dave-the-scientist t1_jbqteik wrote

When you hear "consume" or "metabolize", it doesn't just mean destroying or altering a molecule. The important bit is that energy is removed from the molecule and used by the "organism" in question. Fire definitely does count for that particular one, as the reaction to burn something is almost exactly what we do in our bodies. We burn our food, just much more slowly. A prion though, does not meet that criteria. It does alter a molecule (the non-dangerous form of the prion protein), and energy is removed (the dangerous form of the prion is at a slightly lower energy level, I believe), but the original prion doesn't do anything with that energy. It is unchanged.

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Elladan71 t1_jbrnlfg wrote

I think you're on the right track, here. A virus needs a cell to function. A bacterium needs a nutrient-rich environment to function. An animal needs gravity oxygen, water, and food. Plants and animals are *environments for other kinds of life, so it's no wonder that the question is difficult to answer. When asked in the other direction, you're confronted with whether the Earth itself is alive.

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theSPOOKYnegus t1_jboxtqq wrote

Viruses aren't dead but they don't fit the definition of alive either, it's just a coded set of genetic information that uses the cells processes to reproduce. They float without direction until they hit a cell they can hijack

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Krail t1_jbrbzeh wrote

I've heard one interpretation that a virus particle could be thought of as analogous to a seed, and that an infected cell effectively becomes a virus organism.

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rickdeckard8 t1_jbp807r wrote

Everything alive is dependent on something else in their environment to stay alive. If you define life by function instead of properties you can arrive at a different conclusion.

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czyivn t1_jbp0x3h wrote

The problem is that parasites can range such a gamut that range from selfish genetic elements like transposons all the way up to like, head lice and remora. It's not clear where the line is between organisms and not, because it's really a gradient that depends on your opinion to draw a line. "Capable of living on it's own" is a good line to draw, though, when you're asking how many genes you need to live. It would be like asking how much money you need to live in NYC and including people in a survey who live with their parents. Not totally relevant to the question being asked.

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Awwkaw t1_jbowzou wrote

No, but a virus doesn't have the ability to reproduce. It has the ability to be reproduced. But so does many things, such as chairs, phones, books, and possibly other stuff. Much like a virus however, neither chairs, phones or books can reproduce.

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sfurbo t1_jboxrx0 wrote

Viruses require very specific environments to reproduce (the inside of the right kind of cell), but so does humans. Put humans in 2000 degrees, and they won't reproduce. Put them in the vacuum of space, and they won't reproduce. Without food, humans won't reproduce. Without water, humans won't reproduce. How is that fundamentally different from viruses?

A much more convincing argument for viruses not being alive is that they don't have a metabolism.

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Awwkaw t1_jbp08d0 wrote

In those conditions humans are dead, so they do not fulfill the definition of life.

A virus has no ability to reproduce, and as such it is not life.

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sfurbo t1_jbq50cl wrote

The virus can reproduce, it just requires a very specific environment to do so, including specific molecules that are only produced by other life, such as ribosomes.

Humans require very specific environments to survive, including a long list of chemicals that are only produced by other life, such as vitamins.

The requirements for the virus are a lot more specific, but there is nothing fundamentally different in them.

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Awwkaw t1_jbq6bqd wrote

No, the virus cannot reproduce.

It simply does not have the parts to reproduce. Only instructions on how to produce it. A virus is even worse at reproducing than Ikea chairs:, the chairs bring both the parts and the manual, the virus only comes with the manual. The extremely specific conditions you mention do not allow the virus to reproduce, it allows the host cell to produce the virus.

You might not like the definition of the word, but it is what it is.

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Solesaver t1_jbp0b4x wrote

A chair requires a very specific environment to reproduce. Inside a carpentry shop with a human carpenter capable of measuring, cutting, and machining new parts to assemble, or otherwise a factory designed to create more chairs. /s

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SirNanigans t1_jbr0i9b wrote

Viruses can be fairly complex, but imagine the very basic form of what they are: A string of DNA floating around and getting into cells, and causing them to produce more copies of itself. Obviously viruses are more than just rogue DNA, but that's their function - they corrupt other cells. They don't eat, photosynthesis, reproduce, etc. They're much closer to a chemical reaction, like how fire causes wood to create more fire, except orders of magnitude more complicated.

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LTEDan t1_jbqhwx4 wrote

This probably gets into more philosophy than science maybe, but there's not really a clear-cut line between "life" and "non-life" which is why it's hard to classify where viruses fall. If you instead think of life as less of a binary state and more like a process of self-preservation/self-propagation, then viruses certainly fit that bill. I would imagine the usage of the term "organism" predates thinking of life as a process and more of a state.

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stellarfury t1_jbqop8n wrote

I honestly think that most microbial stuff (prions, viruses, even bacteria to some extent) is closer to machinery than anything a layman would consider "life."

Sure, it's autonomous self-replicating machinery that actively seeks and processes its own fuel, but... well, you could design a macroscale machine that does this.

You wouldn't want to, because you'd be Ted Faro, but it's possible.

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Elladan71 t1_jbrpzwp wrote

Heck, who's to say that having achieved sapience, those self-replicating machines aren't alive? Racists, that's who!

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