Origin of Virus
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The origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids – pieces of DNA that can move between cells – while others may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity.
WIKI
WIKI
Where did viruses come from? (Scientific American)
Ellie said:
No. Also viruses likely have many origins as they have a level of genetic diversity not seen in other true living creatures, many viruses have completely different genetic structures and the only feature they have in common is being genetic packets that lack any metabolism of their own, that reproducing by infecting host cells and manipulating the host cells to manufacture more viruses.
river-wind
Valued Senior Member
For years I thought that RNA viruses may be an example of a second round of abiogenesis; a novel form of life made of nothing more than rudimentary genetic material and a protein coat. After learning more about DNA viruses, however, I'm less inclined to support the abiogensis method, and more towards the plasmid method: rouge bits of RNA or DNA that, instead of transferring to another bacteria as is normal, struck out on thier own.
They have all the hallmarks of life at certain times, but not always. To complicate the question of if viruses are alive is the similar questions: are prions alive? They don't even have hereditary material or a coating of any kind. No homeostasis. But they reproduce. Where exactly does life diverge from non-life?
They have all the hallmarks of life at certain times, but not always. To complicate the question of if viruses are alive is the similar questions: are prions alive? They don't even have hereditary material or a coating of any kind. No homeostasis. But they reproduce. Where exactly does life diverge from non-life?
I wonder how soon an exception will be found - why shouldn't a virus generate just one protein and secrete it, for instance? Ribozymes may very well exist in viruses.
Thats a good question. I used to think that viruses weren't life, but my coursework made me ponder this. Viruses are really important in many ecosystems, some of them can be quite complex, and they are all very dynamic from an evolutionary perspective. I don't know if that constitutes life. :shrug:
An account of the world’s largest virus has just been published. Infectious reading! 
The journal article:
Distant Mimivirus relative with a larger genome highlights the fundamental features of Megaviridae
http://www.pnas.org/content/early/2011/10/04/1110889108.abstract
Some popular science coverage:
Megavirus May Be Stripped-Down Version of Normal Cell
http://www.wired.com/wiredscience/2011/10/megavirus-cell-evolution/
World's largest virus proves giants came from cells
http://www.newscientist.com/article/dn21027-worlds-largest-virus-proves-giants-came-from-cells.html
Please welcome Megavirus, the world’s most ginormous virus
http://blogs.discovermagazine.com/loom/2011/10/10/please-welcome-megavirus-the-worlds-most-ginormous-virus/
The journal article:
Distant Mimivirus relative with a larger genome highlights the fundamental features of Megaviridae
http://www.pnas.org/content/early/2011/10/04/1110889108.abstract
Some popular science coverage:
Megavirus May Be Stripped-Down Version of Normal Cell
http://www.wired.com/wiredscience/2011/10/megavirus-cell-evolution/
World's largest virus proves giants came from cells
http://www.newscientist.com/article/dn21027-worlds-largest-virus-proves-giants-came-from-cells.html
Please welcome Megavirus, the world’s most ginormous virus
http://blogs.discovermagazine.com/loom/2011/10/10/please-welcome-megavirus-the-worlds-most-ginormous-virus/
An account of the world’s largest virus has just been published. Infectious reading!
The journal article:
Distant Mimivirus relative with a larger genome highlights the fundamental features of Megaviridae
http://www.pnas.org/content/early/2011/10/04/1110889108.abstract
Some popular science coverage:
Megavirus May Be Stripped-Down Version of Normal Cell
http://www.wired.com/wiredscience/2011/10/megavirus-cell-evolution/
World's largest virus proves giants came from cells
http://www.newscientist.com/article/dn21027-worlds-largest-virus-proves-giants-came-from-cells.html
Please welcome Megavirus, the world’s most ginormous virus
http://blogs.discovermagazine.com/loom/2011/10/10/please-welcome-megavirus-the-worlds-most-ginormous-virus/
This is probably premature speculation, but is it a possibility that all viruses are so derived, i.e. continued divesting of genes such that a megavirus becomes a diminutive virus? Or is this 'convergent' evolution, in which some early eukaryotes devolved into a 'mega' virus that happens to look a lot like much smaller viruses.
If so, it's quite possible that the many kinds of viruses are derived from some of the earliest primitive prokaryotic cells, and not just from a presumptive eukaryotic cell such as the Megavirus of the article, creating viruses of both RNA and DNA replication.
It is a dumb question but do viruses have telomers , if so then do they carry a telomerase , . As they break once ( Replicate ) then the next virus will not be the same ?
There is considerable evidence that as bacteria begin to colonize one another there is a high likelihood of genome reduction in the intracellular bacterium. The smallest bacteria are all obligate intracellular mutualists or parasites. Because they spend their entire lifecycle inside of other cells they gradually lose all the genes associated with - cell walls, synthesizing vital nutrients, protecting themselves from predators, navigating the environment, pretty much everything but the most basic requirements of reproduction of their genes.
Next, all it has to do is figure out a way of traveling from host to host - which can happen for instance due to incorrect cell partitioning or secretion.. I think that viruses likely evolved even before this more advanced feature, but I have not read any papers on this subject.
No. Telomeres serve to protect chromosomes from instability as a result of the gradual shortening of the DNA ends through the process of chromosomal duplication/cell division. None of that applies to viruses.
Interestingly, retroviruses have telomere-like repeats at the ends of their DNA segments. These act as recombination points for viral integration into the telomeric regions of the host cell chromosomes.
Wolbachia is a bacteria that can only live inside of another cells. Millions of species are infected with it. It's almost like a virus. Some species have completely integrated the entire Wolbachia genome and it is now a part of that species. Interestingly, some species are so dependent that they can't live without the infection.
Fascinating. I wonder how far back in time they go for infecting insects, etc. A whole new concept in gene transfer.
ricardonest
Registered Senior Member
Thank you for the input.
I have the impression RNA is not stable for long period, yet the retrovirus which is supposedly to be an RNA virus is stable , Is it because the encapsulation package or some other means ?
There is a fairly recent hypothesis that eukayotes (having organelles) arose from prokaryotes that ingested other prokaryotes. The idea is that the ingested cells are stripped down and rebuilt into organelles. That process, if it actually happened, would also have had to contend with the ingested nucleus. If so, extra genes or fragments floating around in the "predator" nucleus also may have contributed for some specialized mutations to occur (pseudo-deterministic as opposed to random?). But, in addition, it seems like a lot of useless (and potentially harmful) DNA would have been left over. So it would seem logical that these cells would eventually stuff the leftovers in vacuoles and expel them. If so, those vacuoles would seem to have been a good breeding ground for primitive viruses, or at least for the raw material from which viruses were able to evolve in some other host or medium.
When I look at a stereo-typical virus, I see a pre-life state. We have some genetic material and a protein coat. To me this appears to be a crude form of genetic material with packing protein similar to the shell of a bug. This external packing state reflects a different configurational equilibrium than normal packing protein, which help to wind up the DNA and end up inside DNA configurations.
In terms of abiogenesis, once genetic material is made available, having proteins around could result in protein sticking to it, rendering the genetic material inert. We have plenty of negative charge on the phosphate to be ignored and coddled like in the lab. This could be a problem but will nevertheless help to preserve it until things change for the better.
What will need to happen is a change within the environmental configurational equilibria. The modern virus, instead of waiting for that change to occur, is a go-getter. By entering a cell it places itself in a new aqueous equilibrium condition where configurational changes can occur allow use of the genetic material.
The reason I see this as pre-life before cells is due to its simplicity.
In terms of abiogenesis, once genetic material is made available, having proteins around could result in protein sticking to it, rendering the genetic material inert. We have plenty of negative charge on the phosphate to be ignored and coddled like in the lab. This could be a problem but will nevertheless help to preserve it until things change for the better.
What will need to happen is a change within the environmental configurational equilibria. The modern virus, instead of waiting for that change to occur, is a go-getter. By entering a cell it places itself in a new aqueous equilibrium condition where configurational changes can occur allow use of the genetic material.
The reason I see this as pre-life before cells is due to its simplicity.
all things are related to each other, to be precise.