[Santalum]

http://www.youtube.c...e=youtube_gdata


In this documentary one scientist described how they constructed an RNA viral genome from various other viruses, placed the artificial viral genome in a 'soup' made from lysed human cells and the viral RNA managed to spontaneously assemble itself into viral particles.


This opens up the possibility that viruses were the first form of 'life' to evolve on planet Earth and that they subsequently became specialist parasites of the higher life forms when they eventually evolved.



Very interesting!

[Mrs Zeta]

This is an example of 'self-organisation' but I cannot see why it indicates that viruses were the first forms of life. Self-organisation can be a property of anything, from viruses and bacteria to societies.

[Santalum]

Mrs Zeta, on 1 February 2012 - 07:31 PM, said:

This is an example of 'self-organisation' but I cannot see why it indicates that viruses were the first forms of life. Self-organisation can be a property of anything, from viruses and bacteria to societies.

The consensus, as far as I am aware, has been that viruses could not have evolved until the first cells evolved.

But if self organisation is a property of viruses, as seems to be the case with the afore mentioned experiment, then logically it is possible for them to have evolved prior to or simulataneously with prokaryotes etc

It would seem that, since there structure is so simple, that it would be easier for a virus particle to self assemble in the primordial soup than it would a more complex prokaryote or archae.

[questionposter]

In order for viruses to have started life according to this notion, wouldn't life have already had to have been formed? It's a paradox...

[Santalum]

questionposter, on 2 February 2012 - 01:20 AM, said:

In order for viruses to have started life according to this notion, wouldn't life have already had to have been formed? It's a paradox...

Well according to the documentary virus particles could spontaneously assemble themselves from the rich variety of proteins, RNA and DNA in the primordial soup that existed before the first prokaryotes or archae had evolved. At the time presumeably RNA and DNA could replicate themselves and transcribe proteins with out the help of surrounding cellular machinery.

[CharonY]

The common factor is self assembly. However, they would be nothing like viruses today. Viruses are highly evolved mobile genetic elements that specialize in hijacking the hosts cells. Early pre-cell life forms would have totally different requirements.

[Santalum]

CharonY, on 3 February 2012 - 02:02 AM, said:

The common factor is self assembly. However, they would be nothing like viruses today. Viruses are highly evolved mobile genetic elements that specialize in hijacking the hosts cells. Early pre-cell life forms would have totally different requirements.

No doubt. Modern viruses have become highly specialised parasites on higher life forms. Even so presumeably even some modern viruses could self assemble under the same conditions as this particular experiment.

[CharonY]

Virtually all viruses utilize self-assembly, but the point is that they utterly lack the ability to propagate. I.e. self-assembly is not a sufficient property of early life.

[Santalum]

CharonY, on 3 February 2012 - 09:51 AM, said:

Virtually all viruses utilize self-assembly, but the point is that they utterly lack the ability to propagate. I.e. self-assembly is not a sufficient property of early life.

Correction on a technicality.......

Modern viruses lack the ability to replicate themselves, without cells, under modern oxidising environmental conditions.

But if you could trasplant them into the oceans of pre-biotic Earth then it is quite possible that some of them could replicate themselves.

Presumeably under specific experimental conditions modern viruses can spntaneously disassemble their coatings thus exposing their genetic material.

This post has been edited by Santalum: 4 February 2012 - 01:16 AM

[CharonY]

Quote

But if you could trasplant them into the oceans of pre-biotic Earth then it is quite possible that some of them could replicate themselves.

I am not aware of viruses that have sufficient enzymatic properties to do so in the absence of dedicated transcription/translation systems. Considering that no metabolism is involved the mentioning of oxidizing conditions does not really to the argument.

Exposing their genetic material to the outside is doing them no good. Again, the whole system is geared towards infecting cells. In a prebiotic system a virus is hopelessly useless. The only commonality is presumably the existence of nucleic acids of sorts, probably with at least partially enzymatic functions and possibly of peptides, again with enzymatic functions.
But they would be certainly not recognizable as viruses.

Just to summarize, the chemical capabilities of viruses is not going to change miraculously to something entirely different just by altering the media or environmental conditions.

[Santalum]

CharonY, on 4 February 2012 - 10:46 PM, said:

I am not aware of viruses that have sufficient enzymatic properties to do so in the absence of dedicated transcription/translation systems. Considering that no metabolism is involved the mentioning of oxidizing conditions does not really to the argument.

Exposing their genetic material to the outside is doing them no good. Again, the whole system is geared towards infecting cells. In a prebiotic system a virus is hopelessly useless. The only commonality is presumably the existence of nucleic acids of sorts, probably with at least partially enzymatic functions and possibly of peptides, again with enzymatic functions.
But they would be certainly not recognizable as viruses.

Just to summarize, the chemical capabilities of viruses is not going to change miraculously to something entirely different just by altering the media or environmental conditions.

The DNA and RNA in modern viruses is entirely chemically identical to the DNA and RNA of pre-biotic earth. So logically it could be replicated with the same efficiency (what ever that was) as pre-biotic DNA and RNA in Earth's pre-biotic oceans.

I guess the difference will be in the self assembly of the protein etc coats. I suspect that the extent that the coats of all modern viruses would be able to self assemble outside the internal environment of modern pro/eu karyotes and in the pre-biotic oceans would vary widely.

This post has been edited by Santalum: 5 February 2012 - 01:12 AM

[questionposter]

CharonY, on 3 February 2012 - 02:02 AM, said:

The common factor is self assembly. However, they would be nothing like viruses today. Viruses are highly evolved mobile genetic elements that specialize in hijacking the hosts cells. Early pre-cell life forms would have totally different requirements.

It kind of sounds like your suggesting viruses are living things. But as far as I heard, there was a consensus that they aren't, or are they?

[CharonY]

Nope, nothing in there suggest that they live. In fact I mentioned earlier that they do not posess a metabolism and I classified them as mobile genetic elements.

It should be noted that classification of life can be a tricky business, if you go down to the biochemistry of it all.

This post has been edited by CharonY: 8 February 2012 - 02:05 AM

[Delta1212]

questionposter, on 8 February 2012 - 12:48 AM, said:

It kind of sounds like your suggesting viruses are living things. But as far as I heard, there was a consensus that they aren't, or are they?

"Alive" is a somewhat arbitrary categorization that holds less fundamental meaning than most people think it does.

[FrankQuietly]

A solution of lysed human cells contains all of the necessary components that viruses need to replicate themselves. This is clear from the fact that un-lysed human cells contain all of the necessary components that viruses need to replicate themselves. Lysing them makes no difference. SO I am afraid guys this is not a case of true self assembly, it is just a subtle variation on the normal virus replication cycle.


And another thing, you could call it bug bear of mine. The argument that viruses cannot replicate without a host means they are not alive is really not a very good argument. This is clear from the fact that humans also cannot replicate without a suitable host, namely a member of the opposite sex. (lets leave out all the modern science test tube baby stuff for arguments sake). Unless the last man standing is indeed considered not alive?


It is more sound to argue the lack of metabolism route. And although I do not know of any other organisms that lacks metabolism functions. The consensus on evolutionary history is that eukaryotic cells formed a symbiotic relationship with mitochondria at some point. And since mitochondria are the metabolic centres within cells it suggests that the first cells lacked metabolism and therefore couldnt be alive. Which sounds like a nonsense.


frank