Science Buddies: "Ask an Expert"

Hi! I am doing a science project involving biofilm, a layer of bacteria colonies that builds up inside of water-pipes. In my experiment i must culture the bacteria, test gram-stain the bacteria and make general identifications of the bacteria. I have a few questions:
1. What kind of agar plate should i use?
2. What specific nutrients does the agar plate need?
3. Can I buy these agar plates commercially? If so, where?
4. Can I buy sterile swabs at the same place?

Your help is greatly appreciated

Hi,
Its easier to answer your last questions first.

There are a number of places to buy pre-poured sterile agar plates commerically. I can't vouch for any of them but searching for agar plates and science fair projects will get a number of sources. Eg.
http://www.sciencestuff.com/ctgy/L-p-Agar
http://www.sciencekit.com/search.asp?t= ... agarplates
You should also be able to buy sterile innoculating loops or swabs from the same suppliers. Or you can sterilze flat toothpicks and use those if you have an autoclave sterilizer available to you that can safely heat things to high temperature and pressure.

Generally the commercially available plates are LB agar. This means that they were made by adding agar powder to LB broth (also known as Luria broth) which is a simple medium that most bacteria types will grow in. If you serach for LB broth ingredients or Luria broth contents you should find what the nutrient content is.

There are other types of agar that can be used as diagnostics, for telling the difference between different bacteria. For example some species of bacteria can grow on blood agar or agar that has antibiotics in it. Try looking at wikipedia to find information on different agar types and the species that grow on them. If you need other types of plates you may have to make and pour your own which will require an autoclave to sterilize the medium.

Remember : Be careful, you don't want to try to culture anything that could be harmful to yourself or others and think about what kinds of safety measures you will need to use when working with the cultures and disposing of them afterwards.

Best of luck,
Caroline