Giant virus qualifies as 'living organism'
Mark Peplow

Huge genome allows mimivirus to make its own proteins.

Roll up, roll up, to meet Mimi, the biggest virus in the world. This monster
has just had its genome sequenced, and scientists say that, unlike its
fellow viruses, it may truly be called 'alive'.

The virus's genetic sequence also holds clues that may explain the evolution
of the very first cells possessing a nucleus of DNA.

Since the 1960s, scientists have argued about whether viruses are living
organisms or just a bundle of very large molecules. Viruses are usually much
smaller and simpler than bacteria, consisting simply of genetic material
surrounded by a protein coat. A virus has to hijack another organism's
biological machinery to replicate, which it does by inserting its DNA into a
host. Bacteria, on the other hand, carry all that they need to reproduce
independently, and thus qualify as alive.

Although it shows all the trademark features of a virus, the mimivirus is
much more complex, says Jean-Michel Claverie, a biologist from the Institute
of Structural Biology and Microbiology in Marseilles, France, who worked on
the sequencing effort. If viruses were cars, Mimi would still be a car, he
says,but it would be a luxury model with more gadgets. "It makes this DNA
virus look like a new kind of parasitic life-form," he says.

Mimi carries about 50 genes that do things never seen before in a virus. It
can make about 150 of its own proteins, along with chemical chaperones to
help the proteins to fold in the right way. It can even repair its own DNA
if it gets damaged, unlike normal viruses.

And although viruses can use either DNA or RNA to carry their genetic
information, Mimi has both. "We are seeing an organism here. There is DNA,
RNA and plenty of proteins," says Didier Raoult, a lead member of the team
from the Mediterranean University in Marseilles, France, who reports the
work in this week's Science1.

Full Text at Nature
http://www.nature.com/news/2004/041011/full/041011-14.html

Comment:
As viruses can't survive without at least bacteria to survive on, it is
likely, in my opinion, that viruses evolved by shedding capacity to become
lean, mean and effective.  So the simplest viruses are probably the latest
models, the most complex are the earliest.  Shedding of capacity to simplify
is a known ability of viruses and has been demonstrated in the laboratory.

Kind Regards
Robert Karl Stonjek
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