Question about competent cells.

Stuart Rison stuart at
Fri Nov 28 06:02:54 EST 1997

This in reply to: 

>From: Wilson <netson at>

>Subject: Question about competent cells

>Date: Thu, 27 Nov 1997 18:05:03 +0800

>Dear all,
>I would like to know the optimium OD (600) to harvest the E. coli.
>cells for electroporation. 
>I have read an article (NAR, 1994, vol. 22, No. 14 p.2857-2858)
>about the preparation of competent cells by calcium chloride method and 
>it mentioned that the cells harvested at OD 0.4 or 0.9 can give higher
>transformation efficiency but I would like to know whether the result 
>can apply to the preparation of the competent cells for electroporation.


As far as my experience goes with electrocompetent  E.coli and from what
I've heard/been told, the best results are obtained with cells that are
growing rapidly.  Mid-log phase is therefore ideal but different strains
have different ODs for their mid-log phase although they all tend to be in
the OD600 0.5 to 0.8 bracket.

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