Bacterial identification & colony counting from a mixture of 5 different bacteria

Emir Khatipov khatipovNO at NOuchicago.edu
Thu Sep 12 12:29:06 EST 2002

You say you will "mix" them together. This means to me that you have pure
cultures and want to study influence of each species on the growth of
others. Is that assumption correct? In this case you could design a
bioreactor with compartments separated by membrane walls and grow each
species in its own compartment and measure optical density to monitor growth
of bacteria in each compartment. There are papers on that subject you will
be able to find at Pubmed or elsewhere. If you still want to mix the cells
and monitor growth, you should seed the mixed culture, grow it at the
appropriate temperature and withdraw samples (e.g., every 15 min, 30 min or
1 hour, etc.) to count the cells by colony counting method using whatever
agarized medium is best (or better _selective_) for each species. If some of
the species have indistinguishable colony morphology when grown on a
particular medium, add specific antibiotic that suppresses growth of one
species while still allows growth of another. I suspect that lactobacilli,
streptococci and actinomycetes should be susceptible to different
antibiotics. You should be able to find that out in the literature.

""Haider, Amir A"" <ahaider at iupui.edu> wrote in message
news:856356A46A33F34C9914B63048CB773E0439D7 at iu-mssg-mbx01.ads.iu.edu...
1-I  want to mix and grow the following bacteria for one of my projects:
Streptococcus mutans, Lactobacillus caseii, S. salivarius, S. parasanguis,
A. naeslundii .
2-After growing them, I need to identify and count the colonies, so that, I
can compare the growth rates under the conditions of my experiment.
Now the question is , what type of agar plates should I use so that I can
separate  and  count them?
ahaider at iupui.edu


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