Science Buddies: "Ask an Expert"

So my science fair project is "What cleaning product is the most effective in killing bacteria?" I rubbed a chopping board with a piece of raw chicken, left it overnight, and cleaned different sections of it with various cleaning products. I used sterilized swabs to swab the chopping board and rubbed them on pre-poured nurtient agar petri dishes (which i ordered online). At the moment they are being stored in a dark place at room temperature because I don't have an incubator. It's been 3 days and I see no results on my petri dishes, and the science fair is in 2 weeks (March 26) . How long will it take the bacteria to grow? Will it not grow if the petri dishes are not stored in an incubator? This is urgent. Thank you

Hi Angie,

Sorry to take so long getting back to you. Are you seeing any colonies now on the plates? E coli will grow at room temp but it can take as long as a week to see visible colonies depending on how cold your room is. If you have a big cardboard box, put a small lamp inside it with a thermometer and close the box. Check the temperature after an hour or so. If it is around 30C then you can wrap your plates in aluminum foil to keep out the light and put them in the box as a DIY incubator. The bacteria will grow much faster if they are warm.

Sybee

Good luck on your experiment! I hope you are beginning to see growth. If you haven't already, I would ask your school or even a neighboring school (perhaps a high school?) to see if you could use an incubator if they have one.

Lily

This is great information.