by Welkin Johnson
It is possible that some viruses evolved from free living organisms, shedding their independent functions on the path to becoming "obligatory intracellular parasites." What minimal steps would be absolutely essential for this process to work in reverse, for a virus to slip the surly bonds of the cell and become an autonomously replicating unit?
Wouldn't becoming free living make the virus into the cell? The virus would need translation machinery, transport, energy metabolism, amino acid synthesis/uptake, membrane synthesis, and division machinery. Couldn't the virus do this by being lysogenic?
Posted by: Ryan | February 09, 2009 at 06:40 AM
Viruses require cells principally for protein production (obviously some viruses have their own polymerases and other nucleic acid enzymes). I would venture that all the cellular mechanisms associated with protein production would be required in order for a virus to be free living. From a structural point of view, this would include ribosomes and a membrane to contain the appropriate enzymes and structural units. Certainly it would also require some basic form of energy metabolism to power the translation as well.
The simplest free living bacteria, Nanoarchaeum, with a tiny 500 kb genome, doesn't have much more than these components.
Posted by: Brandt Levitt | February 06, 2009 at 03:18 PM
The entire mimvirus phenomenon has muddied the water in a deliciously confusing manner.
But I often think about phage Mu---a transposon that has metaphorically grown legs and gained something like independence.
Perhaps there is more than one road travelled to become a viral entity!
Posted by: Mark O. Martin | February 05, 2009 at 11:16 PM