New Virus And The Origins Of Life

[damien james]

Here is excerpt from Discover article

Unintelligent Design
A monstrous discovery suggests that viruses, long regarded as lowly evolutionary latecomers, may have been the precursors of all life on Earth

...with the recent discovery of a truly monstrous virus, scientists are again casting about for how best to characterize these spectral life-forms. The new virus, officially known as Mimivirus (because it mimics a bacterium), is a creature "so bizarre," as The London Telegraph described it, "and unlike anything else seen by scientists . . . that . . . it could qualify for a new domain in the tree of life." Indeed, Mimivirus is so much more genetically complex than all previously known viruses, not to mention a number of bacteria, that it seems to call for a dramatic redrawing of the tree of life.

"This thing shows that some viruses are organisms that have an ancestor that was much more complex than they are now," says Didier Raoult, one of the leaders of the research team at the Mediterranean University in Marseille, France, that identified the virus. "We have a lot of evidence with Mimivirus that the virus phylum is at least as old as the other branches of life and that viruses were involved very early on in the evolutionary emergence of life."

That represents a radical change in thinking about life's origins: Viruses, long thought to be biology's hitchhikers, turn out to have been biology's formative force.

Here is link for full article.

http://www.discover.com/issues/mar-06/cover

I am not sure if this should be in microbiology or evolution thread because it is about both. I thought it very interesting to read.

[David George]

Great news damien james I was thinking when humans would find such a virus looks like my assumptions are good.Really great news man!

[damien james]

Thank you David. Here are some words that I thought were exciting from article:

Mimi's outsize complement of genes—so large that the virus is tantalizingly close to being an independent organism—suggest to many scientists that Mimivirus underwent reductive evolution early on and shed some of its genome, including the genes necessary to replicate on its own.

With Mimi, we've captured by chance a picture of an organism that was undergoing such a reduction, evolving toward fewer genes," says Claverie. "This guy just retained more ancestral features than others." Biologists, Claverie says, can no longer view viruses as random assemblages of genes. "We have to confer to these guys a nobility, a genealogy. Not only a genealogy. They are very ancestral, and their ancestors are at least contemporary with ours and those of all present-day life-forms. Mimi is like the missing link.

[David George]

That is great James may be we can pull some information from this post to the Proto-cell hypothesis.

[alextemplet]

This is certainly very interesting, don't get me wrong, but let's not get ahead of ourselves. Viruses cannot be:

the precursors of all life on Earth

This is impossible; viruses, even this new Mimivirus, are obligate intracelluler parasites. As such, they could not have evolved until after the first cells evolved. It is very possible, as this article states, that viruses evolved from more complex organisms, but they cannot be precursors of life as a whole.

[AstusAleator]

Very interesting.
Makes you think doesn't it. I wonder where in evolutionary time viruses evolved? I wonder if, as they say, they were degenerate prokaryotes, or perhaps random nucleotide sequences capable of invading primitive cells.

hmm food for thought. I like it!

[alextemplet]

Both are possible. Mitachondria and chloroplasts are believed to be prokaryotes that lived symbiotically inside larger cells; it is believed that, after living inside other cells long enough, they lost the ability to live outside and became what we see today. Viruses could've been the exact same, except they harmed and destroyed their hosts rather than helped them. Or they could've been, as you said, random nucleotide sequences; however, given the extreme improbabilities of this, the first hypothesis seems by far the more plausible to me. Either way, viruses could only have arisen after complete cells already existed, and can in no way be considered "precursors" of life.

[damien james]

Viruses could've been the exact same, except they harmed and destroyed their hosts rather than helped them. Or they could've been, as you said, random nucleotide sequences; however, given the extreme improbabilities of this, the first hypothesis seems by far the more plausible to me. Either way, viruses could only have arisen after complete cells already existed, and can in no way be considered "precursors" of life.

Not all viruses harm hosts. only small minority. Human being is infested with viruses that don't hurt it. Majority of viruses are non virulent to host.

You shouldn't be so quick to come to conclusion about virus as precursor. Here is interesting quote from article.

Mimi's outsize complement of genes—so large that the virus is tantalizingly close to being an independent organism—suggest to many scientists that Mimivirus underwent reductive evolution early on and shed some of its genome, including the genes necessary to replicate on its own.

Science is never solid ground and always changing, especially with how we think about virus role in life today. After human genome project, we know human genome is full of viral DNA, and discoveries of new viruses happen everyday. We still have much to learn.

[alextemplet]

Yes, we are learning new things every day, but how can it be possible for viruses to be precursors of life when they require fully-developed cells to survive? This can only mean that they evolved after the development of cellular life, and can in no way be predecessors to it.

[AstusAleator]

I'm with alex on this one.
at best, viruses could be a line descending directly from the first cells to undergo endosymbiosis or endoparasitism.
ultimately, viruses require the structures necesary to drive reproduction.
A virus is to a cell as a floppy disk is to a computer. it has the genetic information, but not the means of interpreting, changing it, or reproducing it.
As we know, reproduction is a key element of evolution. Nothing could have evolved FROM a virus that couldn't reproduce itself, unless the virus has a host.

[alextemplet]

Saying that a virus could exist before cells is tantamount to saying that plant-eating animals can exist before plants.

[David George]

Well Alex I am sorry that I have to disagree with you.Why are you saying that all viruses all parasitic in the mode of nurition.What if the ancestors of virus probably derived energy from chemicals and so they might not need a host for reproduction.They might have evolved to reproduce in a host may be cause it was safer and had all the essential nutrients needed for there growth.It is like bacteria reproducing in conjucation the young ones may not have a good environment but higher organisms lay eggs which provides nutrition and safety for the organism hence the higher organisms can survive better.What do you say Alex,James,Astus.