plating density of e coli

Lauri Lintott llintott at home.net
Wed Jul 25 22:31:24 EST 2001


Hi Wo

Take and OD reading at a wavelength of 600 (you will have to dilute your
culture to get and accurate reading, try a 1/50 dilution).
1 OD is approximately equal to 1 X 10 to the 9th colony forming
units/ml.  You can use this reading to estimate the dilution you will
have to plate to give the number of colonies you want to see.  I usually
plate 3 dilutions, 1 above and 1 below what should give me 100 - 300
colonies per plate.  For me, this usually works out to be 100 ul of a
1/1 000 000 dilution of a overnight culture (give or take a factor of
10).

Lauri

Wolfgang Schechinger wrote:

> Hi all,
>
> I'd like to plate some E. coli on LB-agar (without antibiotics).
> Does anyone know a rule of thumb of how much of an
> overnight culture will produce a reasonable amount distinct
> colonies?
>
> Wo
> [tiss mezzage wahs broduceRd using TYPO GENERATOR zoffwer]
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> Dr. Wolfgang Schechinger
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> Institute of Biomedical Sciences
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