Immortal One-Celled Organisms: Fact or Fiction?

[Max Faust]

Is it fair to say that one-celled organisms who multiply by splitting themselves into two identical entities are, for all practical intent and purposes, immortal?

 

[Dadface]

Is it fair to say that one-celled organisms who multiply by splitting themselves into two identical entities are, for all practical intent and purposes, immortal?

Possibly until something like a strong disinfectant comes along and wipes them all out.

 

[Andy Resnick]

Is it fair to say that one-celled organisms who multiply by splitting themselves into two identical entities are, for all practical intent and purposes, immortal?

Sure- and as another example, I have immortalized cell lines from a mouse. There are organisms that can revert back and forth between an 'adult' and 'embryonic' state.

http://www.criver.com/en-US/ProdServ/ByType/ResModOver/ResMod/Pages/Immortomouse.aspx

http://en.wikipedia.org/wiki/Turritopsis_nutricula

 

[ThomasEdison]

Aren't cancer cells immortal?

 

[Q_Goest]

And then there were the immortal jellyfish.
http://news.nationalgeographic.com/news/2009/01/090130-immortal-jellyfish-swarm.html

The only thing that can kill them are Spongebobs.

 

[Monique]

Is it fair to say that one-celled organisms who multiply by splitting themselves into two identical entities are, for all practical intent and purposes, immortal?

No, because the daughter cell won't be identical.

 

[Andy Resnick]

Is that strictly true? I thought clonal cell lines have, for all practical purposes, identical genomes. I'm sure there's mutations and drift, but I thought that's slow enough to allow me to say that cells from (say) passage #60 are the same as passage #10.

 

[Max Faust]

OK, it seems fair that there will be minuscle changes (of various sorts) over time as cells are splitting again and again, especially if and when the environmental conditions fluctuate. Is there any kind of statistical model for this process?

 

[Monique]

Is that strictly true? I thought clonal cell lines have, for all practical purposes, identical genomes. I'm sure there's mutations and drift, but I thought that's slow enough to allow me to say that cells from (say) passage #60 are the same as passage #10.

That would depend on environmental conditions and cells. In the laboratory you can grow cells under identical conditions, so there won't be rapid genetic changes that take over in the population. When the cells experience different conditions, the changes can be quick. I wouldn't be too sure that passage 10 is identical to passage 60.

From the following article: http://www.nature.com/nrc/journal/v2/n4/full/nrc775.html"

With cell lines, it is possible to go back to the same cancer again and again, and have an endless supply of cells. Genetic drift and phenotypic change will be minimal within a laboratory, provided that the cells are not grown continuously — instead, the cells should be replenished from frozen stocks every few weeks — and standard quality control measures are used.

A chromosomal analysis has shown that "the HeLa genome has been remarkably stable after years of continuous cultivation". However, it is also relatively easy to select strains of HeLa that have particular properties by applying selection pressures — deliberately or accidentally — simply by altering the culture conditions, such as the medium or serum. For example, it is possible to select HeLa cells that grow in suspension rather than attached to the culture dish, or HeLa cells that are resistant to cancer drugs.

 

[Jon Richfield]

A question such as this one does not necessarily have a definitive answer. Suppose that I did a deal with the details and the devil granted me freedom from aging processes. I would carry on with my normal reasonably good health and cell turnover indefinitely as if I were in my twenties.
Within a few thousand years not much of my original body would be left, but I never would have died at any clear point. I would be like the ship of Theseus, or if you want a simpler concept, Washington's axe. But if you asked me whether I thought I was still alive, I would think so. And yet, parts of my tissue would by then be significantly new. And there is the question, not only of my daily turnover of blood and gut and skin cells and the like, but of my non-human cells. What about my mitochondria? What about my gut and skin flora, my normal flora in general? I am more than my cells; I am a community.
These points are non-trivial. Consider me in real life. If I lose a hand, am I partly dead? It would not seem so to me, but any conscious skin cells in the hand would say that it was dying. But subjectively I am the consciousness supported by my brain, and less directly by the rest of my body. Is every loss of consciousness a death?
When I was four I was told that at the age of three I had walked about clutching millipedes and similar little animals; the start of a lifelong affinity for biology.
So? What is the big deal?
The big deal is that at the age of four I could not remember my life and actions at age three. Now, decades later I still remember being four, including at four, not being able being three.
Did my three-year-old consciousness die?
Or what?
I can feel the effect of my brain cells dying as I age.
Those microbes that are immortal, or not, as the case might be; do they reproduce sexually or not? In either case, how much do they change in their lifetimes? What part of their continuity do they lose in their changing? If just some of them die, much as my blood cells die, who or what has died? If one cell has learned something (had some information stored physically in its structure that affects it behaviour) and another cell has learned something different, are they still the same organism? Is the community still the same?
If the answer is "Yes", then who are we to say that we are mortal? Our existence goes back some half-to-three-or-four billion years without interruption, just like the green-peas that we casually eat, endosymbiontic cyanobacteria and all. (If there had been interruption, we would not have been here!)
It is largely a matter of semantics, of definition. What does it all matter, and to whom? Ask your sloughing epidermal cells' opinion. Think of their history and ask yourself whether you are not ashamed to send them out to die like that for your own convenience.

In general, be careful what you ask. How sure are you that you will like the answers?

Cheers,

Jon

 

[Max Faust]

Mr. Richfield, I am definitely certain about what I am asking - and I am equally definitely certain that I want the best answer which is available to me. This isn't a question of "semantics" - it is a question of hard science. What proteins that are gathered in what sequences are able to accurately reproduce that condition? I imagine that for instance stromatolites have been alive for nearly four billion years by now, without changing much, so they are the ancestors of us all. But at some point, all that mono-nucleic repetition got organised into structures that sought other solutions for their reproduction. It all comes back to my principal idea: That life is a local system of negative entropy (Erwin Schroedinger).

 

[Jon Richfield]

Mr. Faust,

>I am definitely certain about what I am asking - and I am equally definitely certain that I want the best answer which is available to me.<

On those points thank you for your assurance. Since I did not think that your question had been any more frivolous than my reply however, you need not have troubled.

>This isn't a question of "semantics" - it is a question of hard science.<

That is an extremely curious assertion. Just what examples of science, hard or soft, could you adduce as illustrations of the investigation or dissemination of empirical or formal hypotheses and conclusions, independent of appropriate, soundly established, semantic conventions? In short, how do you propose to deal with or discuss any aspect of science without knowing and showing what you are talking about? Would it be a misunderstanding on my part to wonder whether you regard “semantics” as referring to “quibbling”? I trust that so far it would, but if not, that you are about to change your mind drastically!

What I attempted to illustrate by way of example, was *not* the nature of life. That had not been the question, after all. The term used had been, not “living” but “immortal”. Semantically this implied in context that the concept of life was taken for granted, and quite properly too, given the difficulty of defining it. Schroedinger’s “local system of negative entropy”, while unexceptionable in its content, it comes perilously close to being content-free. As it stands it might as well refer to a match head, a ripple, or an erect milk bottle. Semantically it amounts to a minimal constraint rather than a definition. Certainly it would be hard to imagine anything living as a local (or for that matter non-local) system of maximal entropy!

No, as I understood the question, you asked whether it would be reasonable to regard certain entities as immortal. In context I made certain semantic assumptions, which apparently were correct, that you had no silly ideas in mind about for example how long the universe would last, or what would happen if someone tried to kill the populations in question, so I avoided such tedious digressions. I did try to illustrate however, that the question did not clarify what definitions (or where no coherent definition was available, what descriptive constraints) should apply to regarding anything as a particular living entity.

Your example of stromatolites for example was unfortunate. As entities, stromatolites were poorly defined at best, and no organism that I ever have seen or been able to imagine could reasonably be described as a son of a stromatolite! Scion of a cell that dwelt in a stromatolite, perhaps, but that is altogether different. You would not say that our ancestors were jungles or a savannahs just because some of our genetic ancestors lived in them, would you? In the last half billion years or more there probably has not been a population of stromatolites of more than a few hundred thousand or a couple of million years old, surviving in adventitious circumstances that repelled grazers and promoted stroma-like accretions. Stromatolites are mainly transient developments where suitable conditions arose at particular times. The famous Shark Bay stromatolite banks seem to be mainly thousands, rather than millions of years old. To speak of them as if they were descendants or continuations of the Archaean stromatolites would make as much sense as talking about the Amazonian rainforest as a descendant of Carboniferous jungle.

This is in sharp contrast to speaking of modern jellyfish as descendants of Ediacaran jellyfish, or Peripatus as descendants of Cambrian Onychophorans. In their case we have strong reason to believe that there has been a genetically continuous line of descent of similar creatures. Whether we regard them as accordingly immortal is a far more semantically fraught matter. Already in this discussion some people have implicitly presented their opinions that a genetic change means that in the examples of interest we are not dealing with immortality but with descent.

Are they right or wrong to assume or assert anything of the type? That is a semantic question. It is not a matter of disagreement over material fact, but over the application of a term. Both sets of concepts are after all, equally reasonable. They do not even conflict. It is a matter of which one has in mind. Whether one nomenclatural criterion or another is the best, is one question, best decided by the greatest usefulness or even democratically or despotically by authorities such as lexicographers. It does not in other ways decide the reasonability of the question. Semantics has to do with the relationship between signs or symbols and their referents. Except in highly artificial cases they can only be settled by convention.

That is hardly worth discussion here. What has to be settled is not “whose term is correct”, but “which (meaningful) concepts apply to which questions, and how is one (meaningfully) to decide on the implications”. *Do* you regard it as meaningful to take a genetic discontinuity as implying the end of a mortal entity? If you do, then: end of discussion, and many would agree with you, for whatever that is worth. Do you regard say, a parthenogenic lizard as immortal because she might produce an egg that is her clone? You are free to do so, but you might find some of the objections to that line of thought difficult to deal with. She might visibly be eaten by a hawk or snake, snatched while fighting her own grown offspring for a basking spot. And her offspring might eventually die of old age, with or without issue. *Someone* there didn’t look very immortal, and *someone* didn’t think she was fighting herself! Here immortality was not well specified; a semantic problem: is the immortality hers or that of her species?

Which of those questions is wrong? Patently neither in itself; not until we can show that one of them does not reasonably match a matter of interest. Standard semantics.

When a cyanobacterium splits, which of the two is the parent? If you cannot answer that, what does your question of immortality mean? If you could ask any of the descendent cells after any number of generations which was the parent, each of them would say: “I was, of course!”

Which of the lizards would say the same?

But if you were to ask: “Does the same genotype still exist as n generations ago?” and conclude “Yes; therefore we have immortality!” then what is immortal? Basically the “germ line” as they called it in Victorian times, not the individual, nor even the species, necessarily.

But then, what if what has survived is the genome with minor changes, possibly progressive changes, as with Washington’s Axe? There is no cogent basis to argue that that is, or is not, immortality. If you were so rash as to disagree, you had better have a short way of dealing with the likes of the Ship of Theseus!

You speak of “What proteins that are gathered in what sequences are able to accurately reproduce that condition?”. Biologically speaking I would love to see you clarify that statement in any way that would make sense in its own terms, let alone philosophical or practical terms. If you did not mean nucleic acids, then it is not clear what you did mean. If you did mean nucleic acids, it is not clear why you see that in terms of immortality in context.

>It all comes back to my principal idea: That life is a local system of negative entropy (Erwin Schroedinger).<

If that is all that you wish to establish, namely that life (whatever that may be) arises from instances of other life (whatever that in turn may be), then your definition of immortality may be invincible, much like Schroedinger’s “definition”, but then only because it is too vague to refute.

As TheLoser points out: “All organisms live to perform a transformation and a food source for others so Life is immortal and then all lifeforms are immortal” That is neither right nor wrong unless you decide what you mean by immortality in context, and when you do, your decision is fairly arbitrary. You must suit yourself and your needs.

All because of insufficient attention to the Semantics.

But it bears the consolation that you are free to define your own answer to your own taste. Only, in that case you had better not care much about the meaning, because then you will have “the best answer which is available to you”. For a more useful answer you first must do the semantic groundwork.

Cheers,



Jon

 

[Max Faust]

OK, I understand that, quite often, "common sense" draws more towards what is *common* than to what is *sense*. In lieu of this, I am willing to subject myself to various forms of "tutoring" by people who know either *more* or *different* things (or both!) than myself. Returning to my opening question, which is about a perceived sort of "immortality" in singular celled organisms, I must confess that my agenda is really a different one, and one which is concerned with an almost metaphysical quality of "will" towards complex systems of "local negative entropy" (life) that I seem to intuitively observe as a quality in matter itself; and my hypothesis is that this is a hitherto undescribed force of nature, which works over very large time spans, and subjected to the existing conditions.

 

[Jon Richfield]

OK, I understand that, quite often, "common sense" draws more towards what is *common* than to what is *sense*. In lieu of this, I am willing to subject myself to various forms of "tutoring" by people who know either *more* or *different* things (or both!) than myself. Returning to my opening question, which is about a perceived sort of "immortality" in singular celled organisms, I must confess that my agenda is really a different one, and one which is concerned with an almost metaphysical quality of "will" towards complex systems of "local negative entropy" (life) that I seem to intuitively observe as a quality in matter itself; and my hypothesis is that this is a hitherto undescribed force of nature, which works over very large time spans, and subjected to the existing conditions.

Mmmm...
Well OK, I guess. You will no doubt by now have recognised that mine was a most unfortunate encounter from your point of view. I have an unregenerate and unapologetic bias in favour of mechanistic, causal (though not in many senses deterministic) universal processes and explanations. I do not deny subjective phenomena such as "will" and other emotions, though I have no idea of how we might ever titrate them cogently. As a computer man with a good deal of varied low level experience, I do NOT regard any form of programming that I have seen as having anything to do with emotion, no matter how closely it might come to bruising Turing's test, and no matter how persuasively, persistently, and pathetically it might argue its own consciousness.

But, as I said, I do not deny the possibility that something of the kind exists in living things, and if so, I do not see how it could not be matched or emulated in some or other mechanistic form.

Life similarly. There might for all I know be some form of phenomenon apart from mechanistic functionality, that we might call "Life". However, I am less certain about this than about "subjective consciousness". However, I suspect that whatever I am dithering over has precious little to do with traditional vitalism, which I never have seen to amount to anything meaningful.

But I freely grant that there are other things that I never had seen that did materialise in the course of events.

As for our mutual misunderstanding, I trust that you agree that it was indeed largely semantic, as fundamentally semantically questionable as your use "*common*" or "*sense*". I for one had no idea that you had a metaphysical concept in mind. I still don't understand why "one-celled organisms who multiply by splitting themselves into two identical entities [might be] for all practical intent and purposes, immortal" in any different way from parthenogenic or indeed sexually reproducing organisms.

Do you see your way to elaborating on the point? I must point out that, metaphysical or physical, I see nothing entropic, informatic or thermodynamic about your use of any of the concepts you have proposed. In fact I cannot even see any metaphysical meaning to them until you can clarify, however vaguely (even as vaguely as I referred to "subjective consciousness") how (if at all) life or immortality could be associated with entities, or what it would mean if it were entity-independent.

Over.

Cheers,

Jon