pH optimum for bacterial growth

Nancy Magill nmagill at
Wed Aug 16 10:00:16 EST 1995

We have been using potassium phosphate buffer at 100 mM during sporulation of
Bacillus subtilis and Bacillus megaterium.  Despite the fact that these bacteria require divalent cations to sporulate, they are sporulating perfectly fine.
In fact, I believe someone else in the lab had trouble using Tris to
sporulate but I am not sure what the results are.    We do autoclave the
pohsphate and the metals separately and add them back just before inoculation.
For another experiment, I found that Spizizen's medium contains even more
phosphate (120 mM if I remember correctly).  So yes, potassium phosphate
buffers can be used.  For us, we want to use nigericin which requires the
presence of K+ ions.  Therefore, this has been the result solution for
maintaining certain pH's.  It really does depend on what you want to do
but if you choose phosphate just be sure to autoclave it separately and add it back.

Nancy Magill

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