In article <9510182216.AA27244 at earth.med.pitt.edu>
bap at MED.PITT.EDU (Bruce Phillips) writes:
>> There are four distinguishing features that are used oroutinely to
> define viruses as compared to bacteria (prokaryotes) or animal cells
> 1. Viruses, unlike bacteria, etc., do NOT Uuse binary
> fission to reporoduce.
>> 2. Viruses are unique in that they replicate by the
> directed synthesis of their component parts which then assemble into
> infectious virus particles.
>> 3. Viruses do not synthesize chemicals of high potential
> energy, such as ATP, etc. While viruses may carry enzymes that utilize
> energy in synthesizing macromolecules, they don't have the [enzymatic] machinery to make ATP and similar molecules. Bacteria and animal
> cells dare able to make such compounds.
>> 4. Viruses, unlike bacteria and animal cells, possess only
> one kind of nucleic acid, DNA or RNA. TIn truth, there is some fuzziness
> to this attribute, but in general it is true.
I would add that (most fundamentally) viruses are always obligate
intracellular parasites, whereas bacteria are often free living. Also,
viruses are essentially without endogenous metabolism outside their
host and are thus considered non-living by many or most biologists or
at least within a grey area of the definition of "life".
David N. Levy
Division of Molecular Genetics
Dana-Farber Cancer Insitute
Boston, MA 02115
david_levy at dfci.harvard.edu