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A Truly Alive Virus
cyclop writes "Microbiologists are puzzled by the genome sequence of the giant Mimivirus. It seems this virus has even more genes than many bacteria, is able to synthesize its own proteins and therefore is, by definition, alive. 'We are seeing an organism here. There is DNA, RNA and plenty of proteins,' says Didier Raoult, who reports the work in this week's Science."
Well, most viruses just have DNA or RNA. They enter a host cell, and the host (or more particularly, the polymerase and ribozomes in it) then proceeds to treat the new DNA as its own, producing the proteins incoded in it, which is mostly things like the protein "package" for the viral DNA. Viral DNA lacks the control sites that prevents normal cells from overproducing any particular protein, so the cell will continue to produce the viral proteins until it dies.
However, this virus is unique in that it can produce at least some of its proteins without a host cell. It's not much, but its still metabolism, so it is alive by definition. However, from what I read in the cnrs.fr link from the article, it sounds like it can't, among other things, produce its own ribosomal RNA (feel free to correct me if I'm wrong, I haven't had biology since high school and there are some big words in that article), so its still dependant on host cells for reproduction, which makes it a virus by definition.