Re: [DIYbio] Re: Culturing antibiotic resistant bacteria on regular media?

In general with a single passage and only ~1 colony selected for sub-work the plasmid will almost always be present; depending on its copy number. However it will lose the AmpR phenotype but not due to mutation.  Without the selective pressure of the antibiotic, the bacteria will not maintain the plasmid as it is at a competitive disadvantage in laboratory conditions. Dennis's answer is mostly correct, but the loss of plasmid is driven by random partitioning not by mutation. For a high copy number origin, like pUC, this loss is very slow since the odds of a segregant are low.

On Tuesday, April 4, 2017 at 12:12:05 PM UTC-4, MC wrote:

I have a very basic question as a beginning bio student: What would happen if you sub-cultured something like E. coli with a ampicillin resistant plasmid that's currently growing on amp LB onto plain LB?

My hypothesis based on my limited experience is that assuming no contamination, it will grow but so will E. coli lacking the amp resistance. But why? Do mutations occur in asexual reproduction for the sake of genetic diversity?

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