Excluding bacteria

Karl Roberts kr1 at PGSTUMAIL.PG.CC.MD.US
Fri Oct 9 07:47:54 EST 1998


In a field setting you are probably asking for the impossible.  I used
soil samples for my work concerning mycorrhizal fungi, but generally if
I wanted to produce and maintain sterile soil, I took samples and
autoclaved them for pot trials.  Even so, I still had to re-introduce
soil microflora in order to meet the needs of my study. Also,
autoclaving releases nutrients into the soil as microbes are killed in
the process, and this may confound results unless controlled or
accounted for in one's design.  If you leave the soil in place at the
study site you can fumigate, but this is a disinfecting process only and 
will not exclude microflora for an appreciable period of time.
Introduction of antibiotics will not accomplish your goal either.  I
suggest you perform som preliminary pot trials to examine the effects of 
various disinfecting and sterilizing procedures, then carefully account
for sources of variance in your field trials.  You might also attempt to 
isolate the various bacterial and fungal species you wish to examine and 
narrow your research to just a few of these species.  I wish you luck
and success with your work.
Karl J. Roberts, Ph.D.

On Mon, 5 Oct 1998, David Hagerberg wrote:

> Hello!
> I'm working with fieldstudies of fungal and bacterial activity in soil.
> Now I would like to keep soil bacterium-free and fungus-free
> respectively in order to study the pure fungal or bacterial activity.
> This seems to be tricky and my first thoughts involve addition of
> specific antibiotics, however I doubt they will stay in my soil-samples
> for any longer period of time. 
> Has anybody some suggestion how to keep soil free from bacteria and
> fungi respectively?
> Sincerely,
> David Hagerberg
> David.Hagerberg at mbioekol.lu.se

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