Science Buddies: "Ask an Expert"

Sir, as part of my Biology Project, i've chose to do on the topic "Effect of acids and alkalis on bacterial growth" from http://www.all-science-fair-projects.co ... 107_5.html In this project they mentioned to use E-coli after preparing the agar plates... What else can i use that is common instead of using E-Coli as it is not available around my vicinity?

Hello SelSolis,

I'm not currently aware of any easily available replacements for E-Coli, but have you tried looking on atcc.org? They may carry e coli (although it might be quite expensive).

Purchasing e coli at http://www.carolina.com/bacteria/escher ... /155068.pr is another, not as expensive option.

Let me know if you need anything else, and always use caution when working in the lab.

Thanks!

Other than E-coli could I use Milk Bacteria? If yes, then what is the procedure to culture milk bacteria on an agar plate?

Hi SelSolism

Your project sounds like it is very interesting. Will has given you some good advice for obtaining the culture of E. coli. Carolina Biological Supply Company also offers E. coli also offers cultures of this organism. The K12 strain is safe to work with and is commonly used in school labs. .

http://www.carolina.com/bacteriophage-h ... ion=e+coli
We don’t recommend working with unknown bacteria. When culturing bacteria, you will be growing them to very high concentrations, and this Is not safe to do with unknown microorganisms. If you want to try something that is readily available, then use the bacteria from yogurt that contains a live culture of Lactobacillus species. .
Here are some additional references that should be useful to you. First is a project from this website on testing the effect of disinfectants that you might want to use as a model for your project. The second link has information on microbiological techniques.

https://www.sciencebuddies.org/science- ... p020.shtml

https://www.sciencebuddies.org/science- ... nces.shtml

I hope this is helpful. Please let us know if you have any other questions.

Donna

Thank You Donna I like the idea of using yogurt. But my question regarding this is am i simply supposed to just inoculate an agar plate with some yogurt?

Hi SelSolis,

You are welcome!

Ideally, you should streak the yogurt culture on an agar plate and isolate one colony. When you do your testing, you should grow a fresh culture in broth for a few hours or overnight so you start your testing with a freshly grown, actively growing culture. The bacteria present in a purchased container of yogurt would be old, with individual cells metabolizing very slowing, so would not give reproducible results in a test.

Do check out the instructions for growing bacteria in the link that I sent to you for more details on how to streak an agar plate and let me know if you have any other questions.

Donna

How would one prepare this broth? do we just mix the yogurt in some water... or?

Here a Youtube videos that should help you. You can use a sterile cotton swab instead of a loop and Bunsen burner, but what you want to do is dip the bottom swab in the yogurt and then transfer a very small amount into a tube of broth.

https://www.youtube.com/watch?v=0odxJy0nR9s

Here’s the technique for transferring from broth to an agar plate. Again, you can use a sterile cotton swab.
https://www.youtube.com/watch?v=hT2CiJzfF9s

Ideally, you would transfer the yogurt to a plate culture, then transfer one colony from the agar plate to the broth. If this is not possible, then just transfer the yogurt into the broth and incubate it overnight before starting your experiment.

What growth medium will you be using?

Donna