Science Buddies: "Ask an Expert"

I have a question. My son is doing the above for his science fair project at school. The tryptic soy agar plates are very expensive and this project calls for 4 packages of ten of them. Each step calls for three plates. Can this amount be lowered? Can the medicine droppers and stirring rods be sanitized after collecting each sample so I don't have to buy as many packages of those? I just don't have the money to spend on this.

One way to reduce the number of agar plates required is to divide each plate into two sections and use each half for a separate sample. You'll need to reduce the number of water drops from three to 1-2 and spread this in a zig zag pattern over half the plate. Be sure to carefully label each half of the plate.

Here's an example of using half a plate for each sample:
https://microgroup3.files.wordpress.com ... g_0047.jpg

Yes, the medicine droppers and stirring rods can be sanitized and used again. However, be careful not to suck water up into the rubber portion of the medicine droppers as these cannot be sanitized and reused.