Science Buddies: "Ask an Expert"

Hello,
I'm using e. coli in one of my science fair projects but I'm only able to work on the project once a week for 2-3 hours. I know you should incubate e. coli overnight but is it possible to only do it for 2-3 hours before putting it in the fridge? or is there a way to incubate it for a week without killing everything off or having too much of it grow (i need to be able to count the colonies)?

Thank you

Hi soapymg,

E. coli will likely overgrow if left in culture at 37 degrees C, the typical temperature at which it’s incubated, for a week. I would suggest starting your culture and letting the bacteria grow 24-48 hours (however long it takes to yield countable colonies). Once the bacteria has sufficiently grown, the plates can be moved to a 4 degree incubator, where they can be stored for several weeks. This will prevent them from overgrowing, and you can count colonies whenever you have a free window of time. Good luck with your project!