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

Lesley Robertson l.a.robertson at
Thu Sep 12 03:21:50 EST 2002

"JEDilworth" <bactitech at> wrote in message
news:3D7FC354.868351B1 at

>> "Haider, Amir A" wrote:

> You will probably need a blood enriched plate to grow these organisms,
> at least from my experience in clinical microbiology. I'm not sure about
> the A. naeslundii - it may need something richer like brain heart
> infusion with blood. Also, you may need CO2 enrichment. Lactobacillus
> species don't grow very fast - not sure about caseii.
I don't know about the last 2, but the other 3 will grow without blood.
Indeed, Lactobacilli like tomato juice! I don't encourage beginners to use
blood plates - you never know what'll turn up and our biosafety laws are now
incredibly strict!

> > 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.

Colony counting is not a good way to compare growth rates - not all bacteria
give 100% recovery on agar, and the results will take several days (at
least) to collect. You'd be better measuring optical density.
Lesley Robertson

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