Australia's Science Forum

Hola!

I have just been given a request to make 200 agar plates... As I have never actually done this before I consulted the bible (the laboratory) and it seems fairly straight forward, however we dont have an autoclave, but I've read somewhere in a forum that you can use microwave instead? Is that correct and do you more experienced lab rats have some useful tips or things to think about when preparing agar plates???

Sassi

Yep, use a microwave or pressure cooker. Microwave is easier if you keep a ready store in conical flasks in the fridge. No. 1 tip: cleanliness! Make sure everything is as sterile as possible, flame the lip of the conical flasks before pouring molten agar, clean hands (disposable sterile gloves if possible) and don't breath on or near the petri dishes. Wait until the agar is about 50deg before pouring into dishes, let set then invert to minimise condensation. No. 2 tip: If you have a magnetic stirrer/hotplate, use it as it breaks down agar particles when the solution is just under boiling temperature beautifully and your arm won't fall off from all that stirring. Try different amounts of peptone/bonox/stock cubes or Vegemite in your mixture. No. 3 tip: when the time comes - dispose of them properly, NOT in the bin. HAPPY HIDEOUS GROWTHS!!!!

Hi Sassi - "what richard said" plus if i have to keep my plates for a few days before use- I store the petri dishes in stacks - wrapping the whole stack in glad wrap and then upside down to keep the condensation off the agar.

sorry sassy - i seem to have forgotten to engage my brain to my typing today - i meant - in the fridge. I really need to go home!

Hi,
Another tip is to sterilise your plates before disposing of them. This will reduce the risk of infection .

I also thought microwaving wasn't sufficient to sterilise and that you are better off using a pressure cooker/autoclave.

Lorrae

We used just pressure cook but some spores can tollerate it for well over 48 hours and survive! Whatever is easiest. I still do both I must admit. I pour them as late as I can to minimise problems.