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Interpreting Bacterial Growth After the Bacteria Has Hade Time to Grow

Postby shanaefraughton » Tue Feb 20, 2018 5:27 pm

I have recently completed my science fair project. I was testing how the chemicals in e-cigarette juice effects the growth of different bacteria in our bodies. I tested E. Coli, S. Pyogenes, and S. aureus. The only problem is that I am having troubles interpreting what the different growth patterns mean. For example, I am not sure if the rings around the sterile disks are bacterial growth or if the rings are areas where the e-cigarette juice has diffused. How should I interpret my data?

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Re: Interpreting Bacterial Growth After the Bacteria Has Hade Time to Grow

Postby SciB » Thu Feb 22, 2018 8:14 pm


If you could post some photos of your bacterial plates showing the zones of inhibition it would be helpful. What you should see is a clear area (no bacteria) around the filter disk if there is inhibition.

Did you get a good 'lawn' of bacteria on the plate? How did you spread the culture? What temperature did you incubate the plates at and for how long? If the cultures were too old they may not have grown well enough to see inhibition. Did you have a positive control disk containing a compound that you know inhibits bacterial growth? This is the one you should compare the others to because you know that is has to show inhibition because it contains an antibacterial compound.

Post again with answers to our questions and we will try to help you.


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