The monocultures have been explained as originating with just one bacterial individual.
Without mutations (of some sort) the genetics of it's decendants must be the same as that individual.
There are two choices regarding the antibiotic resistance of that individual:
Either it is resistant or it is not resistant.
The above discussion presumed it was not resistant. In which case the expected result without mutations is that all of the monoculture would be killed by a dose of the antibiotic.
The other case is that it was resistant. In which case all of the monoculture should NOT die but should all live.
If I recall other discussions of this further tests are conducted. For example, after the first antibiotic application one of the survivors is taken and used to produce a monoculture. Now we know that we have started the experiment over again but this time with an individual bacteria that is resistant.
The prediction would be that a much larger number of the monoculture will survive the antibiotic. There may be some mutated ones that do not have the resistance. That is what happens.
In fact, that is exactly why we now have "super bugs".
I don't understand this at all. The number of colonies that have survivors (and the number of survivors in any colony) will depend on how likely the mutation is and whether it is detramental (and to what degree) in the absense of the antibiotic.
Apparently (I'm not an expert) many of the mutations supplying antibiotic resistance are not beneficial or neutral in the absense of the anitbiotic. This suggests an obvious strategy: stop using a particular antibiotic for some years and let selection weed out the bacteria resistant to it so it can then be reintroduced.
This message has been edited by NosyNed, 04-12-2005 09:45 PM
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