Summary:
In general, bacteria (approximately 1µm = 1000nm) are bigger than the largest viruses (approximately 0.3µm = 300nm). The exception are a few types of specialized bacteria (the chlamydia and the rickettsia) which are 0.2-0.4µm (= 200-400nm) in size.
However, ALL bacteria are much larger than the smallest viruses (approximately 0.025µm = 25nm).
"Ultrafiltration" can be used to remove bacterial contamination but is not practical to eliminate viruses.
Ultrafiltration is very useful for sterilization in SOME circumstances, e.g.
where the solution to be sterilized contains heat-labile components. However,
ultrafiltration has its limitations:
- It does not remove viral contamination
- It can only be used for liquids
- It is a low throughput method best suited to small volumes of fairly clean liquid, since the tiny pores in the membrane become easily clogged.
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