MadSci Network: General Biology

Re: what if I don't have an autoclave?

Date: Tue Feb 3 16:23:33 2004
Posted By: Chris Reigstad, Grad student, Molecular Biology and Pharmacology, Washington University in St. Louis
Area of science: General Biology
ID: 1075835700.Gb

Hi Shelly,

As an alternative to an autoclave, you could use a filtration apparatus for sterilization of 
liquids used to make the broth and add agar to this broth, then microwave the mixture 
to dissolve the agar. Assuming the agar is sterile and the filtration works appropriately, 
you should have sterile nutrient agar that can be poured into sterile Petri plates to solidify. 
If you don't have access to a vacuum and/or a sterile filter, you may be able to get away with 
just boiling the mixture in the microwave. However, this may not work, depending on what 
is contaminating your reagents. Regardless of your method, you should put a couple of 
prepared agar plates or media at 37C overnight to make sure no visible colonies of 
microorganisms form (a negative control). If all else fails, you could order pre-poured agar 
plates from one of many online lab supply stores.

Good luck!
Chris Reigstad

P.S. It looks like various models of pressure cookers (essentially the same as an 
autoclave) are available for less than $100--this could be a valuable investment for your 
science classes at Glades Day School.  Check with manufacturer regarding temperature 
(autoclaves should heat to at least 121C (250F) at 15 psi).

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