Science Buddies: "Ask an Expert"

I am currently working on a science fair project called Acne. I have completed grow my E Coli bacteria but I am not sure if what I am seeing is a uniform lawn of E Coli. On my nutrient agar plates I have small clear circular circle about 1mm in diameter over the surface of the nutrient agar control plate. Is these colonies of the E Coli bacteria or do I have to redone these plate. I want to know what exactly I am suppose to see if I have an sucessful growing bacteria lawn.

Hi,

Have a look at the pictures on this page:

https://www.sciencebuddies.org/science- ... ates.shtml
We describe the bacterial growth as a "lawn" when the individual colonies have grown so big that they touch each other and it is difficult to determine the individual colonies - much like looking at your lawn makes it hard to see thje individual blades of grass. Does that help?

Let me know if you have more questions, ok.

Thanks,
Tonya

Hello there,

We would be able to provide more helpful advice if you let us know what your question, hypothesis, and experimental procedures are. What kind of method are you using to look at the effect of acne treatments on E. coli? When you said that you are growing your E. coli lawns, are you doing it without the acne treatment first as a trial run to make sure that you are growing the lawns correctly? Or have you added acne medication to them?

Post back with more details and we'd be glad to help you with any further questions if you need the help!

Best,
Connie

In molecular biology lab, we prepared serial dilutions of bacterial cultures. Sometimes bacterial lawns appear, because bacterial concentrations are too high. To obtain a desirable concentration at which bacterial colonies can be counted, you could prepare a serial dilution by taking an aliquot of a bacterial culture and then diluting it. For example, say I mixed 100 ul of bacterial culture with 900 ul of LB broth. I would take 100 ul of this mixture and add it to 900 ul of LB broth. I would continue the process until I get a certain number of dilutions. I would then spread each dilution onto the bacterial culture. Hope this helps.