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"It's really interesting, and a completely different way of seeing viruses," said microbiologist Didier Raoult of the University of the Mediterranean in Marseille, France, who was not involved in the research. "It's a completely new field that is emerging."
These viruses "are probably playing a big role in the genetic diversity of organisms in the ocean as well," said microbiologist James Van Etten of the University of Nebraska, who also did not participate in the study. Not only can viruses take up genetic material from their hosts and other organisms, but they can donate genes, as well, he said.
"If you're teaching a beginning virology course now, it'd be pretty hard to ignore... that there are these very large DNA viruses in nature," said Van Etten, who edited the PNAS paper.
Over the past decade or so, scientists have slowly begun identifying viruses that defied the conventional idea that they were tiny infectious agents with highly streamlined genomes. In 2004, researchers discovered and sequenced the 1.2 million-base pair genome of the largest known virus to date, the mimivirus (although still dwarfed by sequenced multicellular organisms, whose genomes usually exceed 100 million base pairs). This virus, and most of the other recently discovered giant viruses, has been found in amoebae, which are sometimes referred to as "melting pots" because of all the microorganisms they ingest. Inside the amoebae, these viruses and bacteria may exchange their DNA and grow their genomes.
The new giant virus, dubbed CroV, is the first to be isolated from a marine organism -- a microzooplankton called Cafeteria roenbergensis. They are major consumers of heterotrophic bacteria and phytoplankton, and thus critical to maintaining the delicate balance of marine food webs.
Once thought not to exist in marine environments, scientists now realize that there are some 50 million viruses in every milliliter of seawater. Every day, marine viruses kill about 20 percent of the ocean's microorganisms, which produce about half the oxygen on the planet.
"These [viruses] are major players in the global ecosystem," said study author and marine virologist Curtis Suttle of the University of British Columbia.
Like amoebae, C. roenbergensis harbor many microorganisms simultaneously, making them "a good place to exchange genes," Raoult said. "When you live in a phagocytic protist, such as this one, you meet a number of microorganisms, and then you can exchange genes and get a bigger genome."
Indeed, of the 500 protein-coding genes Suttle and his colleagues found when they sequenced the virus's genome, about half were similar to those in eukaryotes, bacteria, archaea, and other giant viruses. Those with known function included genes that code for translation factors, DNA repair enzymes, ubiquitin pathway components, and tRNAs.
"We're finding suites of genes that you would really never expect to find in viral life, but would expect to find in cellular organisms," Suttle said.
"It is exciting to verify that [these large viruses] are out there," Van Etten said. There are likely many more, he added; "it's just a matter of people looking."
Editor's Note: A 2005 paper in Science also found a large DNA virus in marine microalga. The Cafeteria roenbergensis virus discovered by Suttle and colleagues is in fact the largest marine virus found to date, with a genome nearly twice the size of any other sequenced marine virus. There is no official definition of "giant virus," and conservative researchers would only include the Mimivirus and Mimi-like viruses (such as CroV), according to coauthor Matthias Fischer. As a result, some would indeed call this the first "giant" virus found in a marine organism.
Related stories:
[7th December 2009]
[6th August 2008]


[Comment posted 2011-02-15 13:39:54]
[Comment posted 2010-11-07 20:42:35]
[Comment posted 2010-10-28 01:42:33]
i was probably miss understood your point of view in your first comment. i'm really apologize for that. but as what i had read. i really feel that science issue write with easy understanding words. even its mean you have to said virus are clever. it is easier to understand that way. it was how my Biology teacher though me. i think it is easy to understand and remember them. like sometime i imagine that an antigen is like a police man though.
i'm not a scientist. only a high school student and i found it very hard to read any science issue that write down very hard and i alway gave up half way. ^-^
[Comment posted 2010-10-27 15:22:03]
"Of course, evolutionary biologists do not deny that viruses have had some role in evolution. But by viewing viruses as inanimate, these investigators place them in the same category
of influences as, say, climate change. Such external influences select among individuals having varied, genetically controlled traits; those individuals most able to survive and thrive when faced with these challenges go on to reproduce most successfully and hence spread their genes to future generations. But viruses directly exchange genetic information with living
organisms?that is, within the web of life itself. A possible surprise to most physicians, and perhaps to most evolutionary biologists as well, is that most known viruses are persistent
and innocuous, not pathogenic. They take up residence in cells, where they may remain dormant for long periods or take advantage of the cells? replication apparatus to reproduce at a slow and steady rate. These viruses have developed many
clever ways to avoid detection by the host immune system?essentially every step in the immune process can be altered or controlled by various genes found in one virus or another."
I call attention, here again, to Villareal's statement that, "...these viruses have developed many clever ways to avoid detection by the host immune system..."
Whether or not you believe that viruses are living organisms, precursors of life, seeds/spores, or chemistry sets in a protein bag...there is one thing that is certain: viruses are not sentient - they cannot be clever, devious, evil or malevolent. Perhaps you feel that I am over-stating the obvious, here?
To all those who chose to make commentary on my first posting: you have missed the point of what I said. You attack my take on viral theory, which has little to do with why I opted to post a response to this article.
Yes, you are all correct. I am by no means a virus expert, not a world-class cell biologist, not a guru on infectious diseases; I am only a learner...and not yet learned. Very well, fine. I am no one of consequence. Also fine. All of you are the experts; I concede you that. Factually, I know little about anything, save that I am able to recognize that what we state, publish, broadcast as scientific fact - when it is anything but - is irresponsible reporting.
Consider that not everyone who reads what you write, listens to your lectures, sees you being interviewed on television or hears you on the radio is as well-versed in your science as are your colleagues and you. Indeed, and perhaps surprising to you - the vast majority of your audiences are not members of your scientific and medical communities, they are from among the general lay public. Herein lies the crux of my message...what all of you failed to note and acknowledge. We all have a responsibility to this larger audience to take care with our reporting of facts, versus the reporting of our opinions, hypotheses, dogma, and conjecture.
As regards what is fact, fiction, hyperbole or hypotheses concerning viruses: this is virtually irrelevant to my main concern and sole reason for posting a comment here, in the first place. It is interesting, if unsurprising to me, that none of you - who readily attacked my perspectives on viruses - even took note of (or if you did notice, chose to address) the far more significant and challenging issue of how we differentiate between fact, hypothesis and opinion when we report on Medicine, the Sciences and Technology issues.
Sincere thanks to all of you for seeking to further educate me on viral theory. Perhaps you, collectively, would also consider taking the lead in championing the cause of reporting on scientific/medical fact, when you report on Science and Medicine?
Respectfully submitted,
Dr. Jonas Moses
[An aside: Dr. Suttle, I would be most interested in sharing a conversation, offline, regarding your scientific views. Please let me know how we might connect? Thank you.]
[Comment posted 2010-10-27 10:29:35]
[Comment posted 2010-10-27 10:08:35]
[Comment posted 2010-10-26 22:45:23]
@Moses: We have no universal definition of life, nor do we have a discipline-spanning theory of life (because we perform science as discrete businesses serving disparate markets rather than as the orthogonal and cooperative pursuit of knowledge per se that the promotional brochures would have you believe). Perhaps such facts tell you something about the human-centric view of nature.
[Comment posted 2010-10-26 21:44:09]
Phil Harriman, PhD
[Comment posted 2010-10-26 21:11:39]
i think they kind of between the two major.
seriously we can't say it a non-living thing. in my part i voted for virus is a living thing.
1. it contain DNA
2.it maintain order inside their body.
3.living thing develop and respond . virus can mutate and fight immune system
4.it reproduce (even thought it needs host)
5.virus have traits that evolved over time . see HIV virus was an evolution form Simian virus!!
i don't know a lot about virus but i think it is one kind of living thing...
if you are saying it is non living thing how can we explain why it contain DNA , reproduce , and have evolution?? look at rock ,river , sand! they are non-living thing. they don't have any revolution and can't respond to the signal either. but virus can. how can we say it is non-living thing though.
i think if we can't not put it in living or non-living group. why don`t we put it in another group though. saying it is living or non-living can`t give us any real answer.
sorry if i said something wrong.
[Comment posted 2010-10-26 20:42:01]
---but why mimivirus has around 900 protein-coding genes?? read this from Virus's virus
sorry my question is kind of weird but i really want to know it.
[Comment posted 2010-10-26 19:48:21]
LINK
LINK
[Comment posted 2010-10-26 16:32:54]
"...viral life...?
This statement was culled from the last few sentences in the article, written by Jeff Akst. I feel compelled to point out to Mr. Akst that he failed, in fundamental way, to call out another scientist on a serious flaw in the way people think about viruses: There is no single piece of evidence that suggests viruses are living things, or can be considered organisms. As recently as today, I had this same conversation with a medical scientist. Viruses plainly do not meet the classical definition of what constitutes "life": they do not respire, do not undergo sexual or asexual reproduction and do not metabolize.
We must, in the name of Science (a capital "S,"with intention) and the Scientific Method, put a stop to sloppy reporting of medical and Life Sciences facts. When trained, educated scientists not only mis-speak facts but allow the perpetuation of non-scientific statements and ideas, the entire lay public is done a huge disservice. Please, let us identify the opinions, the factoids, the hypotheses, the dogma, the "truths" for what they are. When we report on them, we must label them appropriately. We must clearly separate statements of fact from all other statements, opinions or observations.
I am horrified at the absolute drivel that passes for statement of scientific or medical fact - especially in the Media, and prominently as regards cancer and infectious diseases. On a daily basis, one or another scientist or physician is being interviewed and makes a patently wrong and misleading statement, such as "this virus is very smart...it has cleverly mutated so as to be resistant to current drug therapies."
Even a young child can be made to understand that something non-living, which does not have a brain, which has no cognitive abilities and is incapable of acting even on primitive thought or genetic memory, cannot possibly modify itself to "outsmart" a drug... There is a world - a universe (!) - of difference between drug-resistant strains of bacterium (living organisms) and non-living DNA/RNA strands (viruses).
The ridiculous personification of a simple chain of DNA or RNA is outrageous, ans unacceptable. Yet, when prominent scientists spout such nonsense on television, on the radio or in the print media, millions of lay citizens accept these as statements of fact, and then not only do not question these "fact"...they repeat this junk science to others and also take action in how they live their own lives, based upon what they have heard.
Mr. Akst, time and again you have quoted the misstatements of other scientists, either ignorant of their falsehood (a forgivable, occasional sin, which simply means you did not do your homework) or (in so-doing) blatantly failing to editorialize on statements you must certainly know to be incorrect.
I have made this observation on many occasions - in my lectures, in my television series, in radio interviews and in my scientific writings:
"...we must also acknowledge that there can be no sacred cows, no immutable dogma or doctrine. For, as soon as we cease to question hypotheses and conventional wisdom, we have lost the ability to engage in the most fundamental processes of discovery ? the Scientific Method. When we begin to elevate our paradigms to the status of deities, then we have also made of our science a religion."
Corollary to this idea is how we report on medical and scientific theories, paradigms, dogma and conventional wisdom. All too often - indeed, with alarming regularity - the medical and scientific communities state theories/hypotheses and dogma as facts. Facts exist in a vacuum, in the absence of a human observer. A blending of all electromagnetic wavelengths in the visible spectrum produces white light. That is a physical fact. How white the light looks to one observer versus another, is not fact...for it is relative to the observer's ability to perceive light and color and to process and articulate this information. This is the reporting of perception, not fact.
Mr. Akst, I implore you, as one earnest scientific reporter to another: please stick with reporting the facts. Leave the "truths," "factoids," "opinions," "conventional wisdoms" and "dogma" to Fox News.
Respectfully submitted,
Dr. Jonas Moses
[Comment posted 2010-10-26 14:23:40]
Thanks for reading!
~Jef Akst, Associate Editor, The Scientist
[Comment posted 2010-10-26 14:10:34]
[Comment posted 2010-10-26 12:41:17]
[Comment posted 2010-10-26 12:34:09]
Great things, viruses!
[Comment posted 2010-10-26 12:24:02]
"...there are some 50 million viruses in every milliliter of seawater. Every day, marine viruses kill about 20 percent of the ocean's microorganisms, which produce about half the oxygen on the planet."
[Comment posted 2010-10-26 12:21:18]