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Bacterial Staining and Counting - (Apr/16/2009 )

Hey All, I'm a new user here, hopefully someone can provide a bit of help.

I'm trying to test a bacteria's viability on a specific growth medium. The medium is a solid.

I'm working with an example of a gram positive and an example of a gram negative grown separately.

My questions are:

Once I've grown the bacteria, what is the best way to count them?

I assume a gram stain would work best? A friend suggested using a cytogreen to perform a live/dead count as well.

Would it be best to stain the bacteria right on the medium? It's a non-porous material, so the stain shouldn't hold on it.


I am not sure if I got your question right. But I think the easiest way to find out if your bacs can grow on certain media is to make a defined suspension of each of your strains, plate a defined amount (i.e. to get app. 50 colonies per plate) on the media to test AND a the same suspension as control on standard media you know your bacs grow. Do this in lets say 5 paralells, incubate the time your bacs need to form visible colonies and count the colonies.
Then compare the CFUs on your control to the media you want to test. You will see if they are growing better or worse or similar......and if they are growing they are viable :blink:

Hope this helps?