Virus: A Living Entity?

OMG!

Science is on the decline! No it is on the incline! Maybe it is both! No it is neither!

I'm so confused ... lets change the scientific laws and principles:

what happened to the concept that all living things consist of cells?

Like I said red, I'm not arguing, I'm simply providing AH with a list of scientists that need to be corrected. There are recently published and peer reviewed papers floating around that are running contrary to what AH knows to be true.

The early evolutionary appearance of viruses The organismal timeline inferred from tRNA sequence and structure showed Archaea was the most ancient superkingdom but established that viruses were also ancient. Viruses are relatively simple living entities and in many cases maintain a regular structure. They have long been considered fragments of cellular genomes and not living organisms and were generally excluded from consideration in evolutionary scenarios of the tripartite world, despite being important components of the biosphere. The importance of viruses and their potential roles in early cellular evolution were recently reevaluated. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2265525/

Thanks to everyone for the responses. I'm pleasantly surprised that my question generated so much interest. I have learned a lot more about viruses, DNA, etc. in the last couple of days.

In future classes I will mention that there is disagreement in the scientific community as to whether a virus is a living entity or not.

Thanks again.

Good thread Don. I've learned a lot too.

It doesn't take much to get this bunch going...............myself included.

I now know more about viruses than I ever thought I would. I'll be able to impress my non-digitized friends at our next beer drinking session with my vast array of knowledge.

I agree Red. I'm sure that somewhere, in someone's backyard, swamp, or tropical forest, something is evolving into something that we have never seen before.

GA. Your summation supports the posting by Kramarat #36 and the Scientific American article. If we are to exclude any faith based theories, the arise of the virus to assemble the primordial soup of chemicals including hydrocarbons is a good one that leads to the formation of genetic material. At some point in the formation of the earth, viruses may have not only been the dominant "life" form but the only "life" form. The article from SA refers to viruses as meso life forms. Viruses eventually gave rise to RNA/DNA mostly to protect genetic material they already formed. The take over of the virus products of RNA and even double strand DNA by prokaryote cells and eventually eukaryote (cells with a true nuclei) life forms started some sort of boundary between viral meso life forms, prokaryote , and eukaryotes , is really a symbiotic relationship that persists today. A eukaryote can be viewed as the parasite as well as the virus can be viewed as a parasite. It seems the virologists would solidly agree with you. It is an interesting question, live or dead, or active / inactive. One thing I Know is that viruses are more than machinery if somewhat less than a eukaryotic life form. But we need viruses to survive and evolve. Yes new and primitive life will arise and expect the virus to be central to that evolution.

You wrote, "viruses may have not only been the dominant "life" form but the only "life" form."

This is an interesting thought. Let's go to paragraph three of the Scientific American Article provided by Kramarat:

"Viruses, however, parasitize essentially all biomolecular aspects of life. That is, they depend on the host cell for the raw materials and energy necessary for nucleic acid synthesis, protein synthesis, processing and transport, and all other biochemical activities that allow the virus to multiply and spread."

If viruses require a host and they preceded all other forms of life it would leave us with a small dilemma - how would they replicate without a host?

Additionally, if viruses were a meso life form, then by that definition there must have been a predecessor because meso means "middle".

You wrote, "Viruses eventually gave rise to RNA/DNA mostly to protect genetic material they already formed."

I am not sure what you mean because genetic material is RNA and DNA.

You wrote, "One thing I Know is that viruses are more than machinery if somewhat less than a eukaryotic life form."

Are they? What constitutes a machine or where does that boundary lie with regard to biology? I would go further and say that even you and I are actually biological machines. complex machines, but machines nevertheless. Again, it just depends on how you define it.

You wrote, "But we need viruses to survive and evolve."

Absolutely. Everything is part of the web of life and everything plays a part.

The second paper makes it sound as though the scientists are leaning toward giving the "lifeform" designation to viruses. Who am I to argue?

Whatever the consensus becomes in the scientific community in regard to viruses, that will be my final answer.

maybe they come up with a third option, un-dead like in zombie?

zombie infestation has similarities with viruses, destroying the bodies they infact, or is it the other way around

Do viruses depend on a host for activation? That is the very essence of understanding early evolution. Patrick Forterre of the Louis Pasteur Institute in Paris is now arguing that the virus was the link between amino acids and the formation of genes. A viral component somehow formed early genes. Which then formed single strand RNA and later for protection the double helix DNA. I view a gene as one manual from a bookcase full of manuals. One gene may make up a single strand of RNA but usually these strands are very long and form the full genome that we know as RNA/DNA. Forterre speculates that the double helix was formed by viruses to protect the packet of genes. Protect it from what; heat, and UV likely. It does beg the question of where do viruses come from? A paper on this subject is published ,

"Did the first virus self-assemble from self-replicating prion proteins and RNA"?

Lupi O, Dadalti P, Cruz E, Goodheart C.

Further in the Scientific American article following your quote is this gem, "Approached from this perspective, viruses, though not fully alive, may be thought of as being more than inert matter: they verge on life". Thus the term meso applied to viruses. They did not have a host in this early stage of the earth's history. Again it begs what comes before them to assemble the molecules in an organized manner? Amino acids and other organic material are components of the primordial soup. But really, What is the spark of life itself? Why did these molecules assemble to form genes? And later DNA.

Forterre does think that the gene was central to all life in the early stages and has traced the origin of many genes back to viruses. He has proposed a new definition of a virus, "... a capsid-encoding organism that is composed of proteins and nucleic acids, self-assembles in a nucleocapsid and uses a ribosome-encoding organism for the completion of its life cycle".That sounds like life to me but it is only a definition.

These viruses are now complementary to most life forms as we now understand it. Could there be other developments of life based on other molecules and the assembly of such? The temperature of early earth was quite hot. Could there have been silicon based life forms rather than carbon. Silicon can be more stable at higher temperatures. Surely we can only speculate what had happened in early earth and how life formed. Viruses are ancient and ever evolving and tracing our ancestral pathway leads us back to them.

Great post, Kevin.

Your questions are good questions that are worthy of debate and continue to be debated.

You wrote, "Forterre does think that the gene was central to all life in the early stages and has traced the origin of many genes back to viruses. He has proposed a new definition of a virus, "... a capsid-encoding organism that is composed of proteins and nucleic acids, self-assembles in a nucleocapsid and uses a ribosome-encoding organism for the completion of its life cycle".That sounds like life to me but it is only a definition."

I think Forterre's definition is good. What a virus lacks is a metabolism. The protein folding and assembly process seems to be chemistry at work. However, tis is not metabolism. Again, you can make the definition of metabolism whatever you want, but it is typically a process that either synthesizes proteins, carbohydrates, or lipids, or it breaks down complex molecules and produces a waste product.

The fact that viruses are obligate intracellular parasites makes it difficult to argue that they preexisted other forms of life. However, I easily see coexistence.

It does metabolise, when it has control of the host cell in-order to reproduce itself.

Is it the virus metabolizing or the host cell?

I think it is the host cell. However, it does pose an interesting twist to the definition.

It seems like the virus is pulling the strings forcing the host to metabolise for the virus so it can replicate itself.

Yes, but it is like walking into someone else's machine shop to make your pet project rather than having those resources yourself. The resources still belong to the host. You just hijacked the production schedule.

Or you can looking at it like a parasite. They hijack their host and get them to produce their food, reproduce for them, watch over their young, etc. Since Viruses don't have the "parts" to metabolism they force the host cell to do it for them.

Exactly. It is just semantics at that point. What do you call a person who overpowers a flight crew and directs control of an aircraft? Hijacker or Pilot?

Both, you can be a hijacker and pilot, but why come up with the apple/orange comparison?

The virus reprograms the host cell so metabolising for both of them; reproduces for it, etc.

I'm assuming that the host cell is considered to be "alive".

Would it be inaccurate to say that the virus is not actually alive in the typical sense, on it's own, but when it latches onto the living host cell and goes through the hijacking process, a life form is created that is part virus and part host, but unique from either of them on there own?

While not "living" in it's solitary state, once it joins with the host, the genetic material in the virus becomes part of the "living" machine that cranks out copies of itself.

The thing that confuses me, is that, that would indicate a survival mechanism that is encoded into the virus in order to perpetuate itself, which I would think would be a trait of a living entity.

I think that maybe when the virus joins with the host, it is the only real time that it can be considered "alive". Without a host, it is dormant and exhibits no signs of life.

You wrote, "that would indicate a survival mechanism that is encoded into the virus in order to perpetuate itself"

Yes, at least in a simple way it is programmed to reproduce.

Yeah. And I'm thinking that the only time that the virus resembles a truly "living" entity, is when it becomes "one" with the host cell.

It all gets fuzzy when you discuss if a virus is alive or not. Let me expand slightly on your idea here. What happens when you define the parasitic life form of a virus as the active form in this discussion and the inactive form as just the seeds of a virus. Then the virus does meet all of the same "life" attributes that the cell had prior to infection.

This is why the author in your Scientific American article pointed out that micro-biologists consider the alive or not status of a virus as identical to the alive or not status of a cells organelles.

It really gets fuzzy when you start thinking about how they got here, the mechanism behind how they got here................and to a certain extent, why?

I've definitely come to understand the conundrum in simply stating that they are life....................and in stating that they are 'not' life.

There sure is a factor of creepiness, to use an unscientific term. This morning I was thinking about The Andromeda Strain...............it's not really that far fetched.

Even though a virus is incorporated into a host when it infects the host, and even though this results in the host creating copies of the virus that are disseminated, that isn't enough to be classified as a living entity.

This can be supported on the basis of convention alone, as there are numerous non-life examples of discrete packages of information which upon exposure infect individuals resulting in copies of the information being disseminated.

Consider a highly addictive drug, like crack cocaine. Can we agree that a crack cocaine rock is not a living entity? Can we also agree that when individuals are exposed the information transmitted sets in motion a process that has been very successful in causing additional copies of the crack cocaine rock to be produced and spread?

Music and gestures are very similar.

All of these including the virus are packages of information that have evolved in a way which promotes production and spread of like copies. None of these are very usefully defined as living entities.

Ah yes, but at the same time all of your non-life examples can also be said to be taking on a life of their own. Just look at this very thread itself. It just won't die.

Too funny!

Thanks. You also present many strong valid arguments. Obligate may not have applied at the beginning because there may not have been any higher life form to be a parasite. If there was a higher life, how then was it formed? It would need the genetic material formed by these early viruses. Zimmerman's book, Parasite Rex is good reading and can redefine parasite for many of us.

It is a fascinating study but I have done very little on viruses, other than a couple of first year courses on microbiology and pharmacology. My aim was always to make sure they were not in someone's water supply. The virus we know today has many life forms to parasitise. Could they exist today without a host, of course they do. Polio virus can still be still isolated in sediments in rivers just waiting for someone or animal to allow it to invade. That is why we keep vaccinating against it. It is also one of many reasons to limit turbidity in drinking water. It seems many viruses can be dormant for extended periods until activated by a host.

An Aside:

Someone keeps marking me off topic. I do not mind that but I expect the perpetrator to have the balls to acknowledge and explain why. If I were to do so, doubtful, I certainly would give them that courtesy. Being off topic can be useful to expand the discussion.

You wrote, "If there was a higher life, how then was it formed?"

I can see that a virus may assemble out of the "soup" by chance, but have no host to reproduce until one assembles by chance.

While it may seem statistically unrealistic, when you have a laboratory running an open experiment for 1/2 to 1 billion years a lot of opportunities may present itself.

Then there is the whole panspermia theory to the start of life on this planet. I really do not find that unlikely at all. Time will tell as we acquire more knowledge and get a better handle on exactly how many precursors of life may be lurking in space.

If that theory proves true then the origin of life could easily predate the formation of our own solar system and all bets are off as to what arrived here first and got a foothold.

Life has proven to be much more robust than we had ever imagined and I am thinking that it may also yet prove to be much more common than we have ever imagined.

Bingo as a GA. If life arose on earth from panspermia, the organism may be very different than we know. Silicon based life forms may have been able to traverse outer space for millions of years, and then they gave rise to viruses. It seems a better topic for another thread but it still begs the question of how that life form, if I can use that term, arose.

"curiouser and curiouser"

"It would be so nice if something would make sense for a change."

Alice in Wonderland.

I'd also agree that viruses are not alive. Aside from normal reproduction and/or mutation, viruses appear to be an ancient "mechanism" by which genetic information can be transferred between living organisms. Is a chromosome considered alive?

While genetic material is normally transferred between similar organisms(species), viruses can exchange bits of genetic material between vastly different organisms. Biologists are currently using the viral injection mechanism to genetically engineer new organisms. This link refers to viruses as "infectious particles".

http://www.ucsusa.org/food_and_agriculture/science_and_impacts/science/genetic-engineering-techniques.html

Some quoted sources discuss live and dead viruses. While "live" does not necessarily mean "life", "dead" does imply previous life. IMO this is just sloppy semantics. The correct terminology when discussing viral efficacy should be "active" and "inactive", not "live" and "dead".

The viral transfer of genetic material has undoubtedly impacted the history of life on this planet and will continue to do so in the future. Like all mechanisms of change, some results are beneficial, some benign, and some very deadly. The common cold, while annoying, is reasonably benign. Other viruses seem to persist (or emerge) and function as a form of natural(?) population density control.

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

Viruses change through errors created by the host cells. This is a random process. The errors that tend not to kill the host will produce more virus particles while those that kill the host too quickly may never be seen again. These changes are the reason new viruses emerge and some species specific viruses can infect new species.

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0004522/

I just don't see any significant comparison between the macroscopic complexity of a plant seed

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

and the inert mechanism of a virus. A seed is a living organism until it is no longer viable. Then it is a dead seed, or possibly beer. Cheers!

If I build a machine that replicates itself, is it considered alive?

When you do I'll bring the beer. ;-)

Almost there...

http://www.youtube.com/watch?v=ZX-iJLHZt8M

These are silent revolutions that are quickly coming on us and are no longer designed for the industrial market, but the home user.

Wow! This thread is quite long and still going.

I was out of town and missed it. And I'm usually late to these parties, anyhow, from email lag and other mishaps.

I certainly couldn't read all the posts and info. referred to, in the time I had this morning. In some ways I'd compare this discussion with the one a week or so ago asking whether Math exists or not.

It is hard to agree to a definition of "life." That is mostly what I see in the posts here. And I suspect the same problems exists in a lot of scientific and medical circles. If there is no bona fide, ironclad definition, doesn't it suggest that it is subjective? Or we don't quite have the proper words to define it? We may feel that we know it. We can agree to some basic or broad characteristics, but in the end can't define life or living. That is more what the posts here have been addressing because it is a prerequisite to discussion -- Initial words and phrases for following words and phrases to depend on.

I like the seed analogy and surrounding comments/questions. The comment "they verge on life" appeals to our common sense -- whatever that is. But we still have no clear definition of "life" and "living" acceptable to everyone. We can certainly reduce life to a mechanical process by some definitions. Thus the number of comments in this thread... which, I suppose, is representative of discussions about the subject.

Seeds, viruses... each waiting for the proper environment to become "active." Except, I think, many would agree, the outcome of the seed's activity leads to what we call a living organism, while a virus only changes processes in a living organism. And changes within its internal structure can nullify its (a virus) ability to be "active." It depends on how you define life and living.

The wild card is that a series of process, in matter, has led to "self"-awareness; a feature of consciousness. What WE KNOW (??) is the result of that. All of this comes about because of that. Or at least in the form we recognize it -- the ability to conceptualize, communicate, record communications, express thoughts, and feelings. What are thoughts and concepts? What are feelings? Animals may experience them but have limited means to convey them to us -- barking, hissing, chirping, whimpering, etc. The discussion is a dog chasing his tail in some respects. The question arises out of consciousness. To me, the more interesting subject/question is in exploring that. (And there is no dearth of avenues to explore.)

Welcome to the carnage. ;-)

You are right that it all depends on the definition of life. I proposed the following:

From the Medical Dictionary:

1. The property or quality that distinguishes living organisms from dead organisms and inanimate matter, manifested in functions such as metabolism, growth, reproduction, and response to stimuli or adaptation to the environment originating from within the organism.
2. The characteristic state or condition of a living organism.
3. Living organisms considered as a group.
4. A living being, especially a person.

That is just one definition and you can pull up many others on the web or make one up if you are so inclined. So, the answer is subjective (if not contentious).

Indeed, the subject of consciousness and its origin is a fascinating subject, but in its own way even more contentious a subject than the definition of life for a virus.

Based on the "Cell Doctrine" or "Cell Theory" established in 1838, the cell is the fundamental structure of all living organisms. A virus does not consist of a cell (or cells) and thus is not classified as a living organism. However, I have always had a problem with this definition, but I guess "an apple is not an orange"!

A final note from me. Most of all thanks to all who responded. I was anxious to log on everyday to see what the latest response was. Again, I am pleasantly surprised at the amount, and depth of thought for the responses.

FWI: The agency for which I teach biological counter-terrorism courses sent a response to me from a staff doctor. He said that although viruses contain "living tissue" they are not technically a living entity. As I stated previously, in future classes I will simply state that there are different opinions in the medical/scientific community on the subject. I think that differing opinions are what drives us to a better understanding of everything.

Thanks again.

Don

One thing about a CR4 thread is that it opens everyone's mind. Once started, you never know where it will end up or what side bars will be opened. Just to throw an added twist, I am expanding AH's panspermia theory of life. I found this on line. I do not fully subscribe to the coincidences of bad things happening whennever comets appear. Many of the problems, the Peruvian incident, may just be a placebo-type effect for the headaches. It opened some doors for me to explore further and I will enhance my future reading with some information about the panspermia theory. Viruses are interesting and their origins are intriguing to say the least. The future may change the definition of a virus. I think they may know they are more important than just being infective.

You're quite welcome. This was a fun debate. I'd like to take the time though to reemphasize a point I made earlier. In the biological counter-terrorism realm I believe that a virus should be considered alive purely because of the replication factor. Unlike a dead toxin that will have a fixed mass and quantity which can be diluted or dispersed below a toxicity level, a virus can multiply and spread to ever larger contaminated areas with little to no reduction in its effectiveness.

My point here is that it is safer to inaccurately attribute a virus the title of living than it is to accurately call a virus as dead and apply the wrong containment protocols.

Great thread. Between here and my other internet reading, I know a lot more about viruses than I ever would have. Unfortunately, I'm left with more questions than answers. To say the least...........they are mysterious little buggers.

Best site of all - all the virology on the www.

Good find!!! I'll have to pretend I didn't see it for now though...........................I'll never get my kitchen done.

Welcome to the continuum fallacy, folks!!

Next up, how many angels can dance on the head/point of a pin?

Although no absolute answer can be credible, I think the weight of most informed opinion is that viruses are not alive. I see little reason at present to expound otherwise, but this could change with future discoveries.

They are alive. What we must to change is the definition of what the life is?

....well, when you put it like that, how could anyone argue with your point?

:-)