disrupting e. coli cells

David LaPorte Biochem david-l at htlv.med.umn.edu
Tue Mar 15 14:58:15 EST 1994

bipin at iastate.edu (Bipin K Dalmia) writes:
>i've never had much success with sonication but since that is the only
>piece of equipment we have at present, do you have any suggestions for
>optimizing e. coli disruption with a sonicator? i've heard that some
>people use lysozyme treatment before sonicating, do you have any
>experience with this?? any other treatments??

Sonication should work well but it can be tricky.  I find the following
to be important:

1. Probe tuning.  Follow the instument manual.

2. Probe placement.  The tip should be just below the surface of the
   cell suspension.

3. Probe condition.  If the probe tip is pitted or coated with metal
  oxides (ie is not shinny), good cavitation doesn't occur.  If the probe
  is not too bad, you can clean it up with emory paper or fine sand paper.

4. Power setting.  If it's too high or too low, cavitation is poor. 

You can tell when it's working by the sound.  It should sound like frying
eggs.  The sound should be high pitched and sharp.  If it sounds like it's
bubbling, you have too much power or poor placement.  

Save a sample from before sonication.  After you've sonicated for a while,
dilute a bit of the before and a bit of the sonicate.  Check breakage
by comparing them under a microscope.

Dave LaPorte
U. of Minn.
david-l at microbe.med.umn.edu

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