Plasmid Prep II

Richard J. Dudley rjdudley at YAHOO.COM
Tue Aug 11 13:11:44 EST 1998

> Dear Dr. Obaid Khan,
> I wonder if you have moulds in your plate feasting on your bugs.
> Smell your plates. They probably don't smell like LB anymore.
>  if rate of consumption < rate of bacteria proliferation
> your miniculture or maxiculture will still get cloudy.
> just that I don't think it's entirely transformed bacteria, 
> but the predators !
> thus, you get less DNA than expected.
> I would check your plates, SOC, stock competent cells......
> Actually, this happened to me once.
> A senior tech and a post-doc noticed the more than usually number of
> "satellites" on my plates and told me that I was 'moulded'.
> I was told to throw away the plate right away.
> I still don't know where I got the mould from......  

I would also make it a point to check the potency of the
antibiotic--how many ug/mg of the ampicillin is truly ampicillin. 
Should say on the label.

pBR322 is a lower copy number plasmid than the newer synthetic
plasmids (pUC, pGEM, pBS, etc).  This may also affect the yield of the

--- --- --- -- -- -- --- --- ---
Richard J. Dudley (rdudley at
Senior Research Assistant
Center for Genomic Sciences
Allegheny University of the Health Sciences
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