Science Buddies: "Ask an Expert"

XXXXXXXXXXXXXXXXXXXXXXX

Hi Pedro-
Both are excellent approaches, but they ask different questions: approach 1 (treating used kitchen sponges with various disinfectants, swabbing them after being disinfected and inoculating the petri dish) asks: which disinfectants are best at preventing bacterial growth? Approach 2 (growing the bacteria directly on the agar plate (without using the sponge) and then put filter disks saturated with the disinfectant right on the petri dish before incubation) asks which disinfectant kills bacteria better? Am I understanding that correctly? If you have the time, you could use both. A third possible alternative is to mix your disinfectant in with the agar on some plates before you pour them (and leave some plates without disinfectant) - then grow duplicate plates with the same bacterial sample - one with disinfectant, one without. What do you think?

Are you going to be using commercial products or purified antibacterials (like chloramphenicol or ampicillin)? Either way- make sure to use controls! Do you have a positive control? Bleach might serve as a positive control, but I'm not sure. Negative controls are just as important.

Good luck - sounds like a fun project!
Stephanie