Smaller than a virus?
Date: November 2003
Are there any other organisms that are smaller or
simpler than a virus?
Not really. A case might be made for a prion, but that gets into the semantic
issue of what you want to call an organism.
Well, that depends whether you think viruses are organisms or not, because not
all scientists agree! But let's say they are for argument's sake. There are
smaller "infectious particles." Viroids are naked RNA that seem to be associated
with disease. And prions are abnormal proteins that seems to be able to induce
normal proteins to become abnormal. An example of this would be Mad Cow disease.
Do a search for prions and you will find a lot of information.
Actually...viruses are not considered "organisms" in the sense that they
metabolize on their own. There are some bacteria that approach the size of
larger viruses but viruses are smaller than bacteria. They were originally
classes as non-filterable organisms because they would pass through filters
that would remove bacteria.
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Update: June 2012