Calculation of transformation efficiency

Kevin A. Mulcahy K.Mulcahy at sheffield.ac.uk
Tue Feb 4 07:51:13 EST 1997


I have been trying to work out how to estimate transformation 
efficiencies but in my searching through various texts I have found 3 
different (and confusing!) ways which all give different answers!. Could 
you please tell me if the calculation written out below is correct?

200µl of E. coli are transformed with 1ng of pBR322, made up to 1ml with 
growth medium for the recovery phase and then 10µl of this plated plated 
out (i.e. 1% of the total transformation mixture, therefore equivalent 
to 10pg DNA used) and 100 colonies obtained. Is the transformation 
efficiency 1 x 10(exp)7 cfu/µg DNA? (i.e. 100 colonies per 10pg DNA and 
therefore 10,000,000 colonies per µg of DNA).

Thanks,

Kevin Mulcahy.



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