Survey: does maltose help or hurt lambda plaque size?

Dr. S.A.J.R. Aparicio saparici at crc.ac.uk
Wed Mar 10 14:36:10 EST 1993


I work in Dr Sydney Brenners lab and I can relate a precis of the reply
I got from him to exactly this question. A lot of Syndeys early work was
with the lambda phages so there is a lot of experience.

: Although maltose does stimulate expression of the lamB receptor, it also
has the effect of rendering the growth medium acid more quickly, partly by
its metabolic byproducts which are acids. In unbuffered media, the pH will
drop below a point where adsorbtion of the phage no longer occurs efficiently.
This fact together with altered gorwth characteristics of the bacteria means 
there is a much narrower window for getting the phage to bacteria ratio correct.

It should be remembered that even trace quantities of glucose will repress the
lamB receptor and this has some bearing on what yeast base is used for the medium.

The control of burst size (to which I think you refer) is controlled by other factors
(plaque density, Chi status etc).

After a period of using maltose and variable yields,  I have now moved to no maltose
with very consistent results.


Dr Sam Aparicio
Molecular Genetics Unit
Cambridge UK
CB2 2QQ

saparici at med.cam.ac.uk



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