Expert: Walter Hintz - 2/22/2007

Question
One more quick question: I have the plates in the oven with the light on with no heat. They are upside down. A few of them are starting to get little dots, and one has 3 big dots. At first I had them right side up, but then I read on the Internet that they were supposed to be stored upside down, so I changed them. There is a lot of moisture collecting on the lids of the plates. If you tip the plates, water will roll around. Is this bad? Is there anything I can do to get rid of this?
Thanks,
Julianne
-------------------------------------------
The text above is a follow-up to ...

-----Question-----
Hi, I read on an internet site that you are supposed to match the temperature of the bacteria's environment. I'm just testing things around the school, does it need to be at 35 degrees celcius? thanks for your help
-------------------------------------------
The text above is a follow-up to ...

-----Question-----
Hi, I am doing a science project, and I am testing to see which area of my school has more bacteria. I am using agar plates to do this. The type of agar in them is Standard Methods Agar. Do you know what temperature I should keep them at to grow the bacteria? How will I categorize the results once the bacteria has grown? Thanks for your help.
-----Answer-----
Hi  Julianne
  Bacteria row best at 3.5 degees C.  I you do not have an incubator keep the plats in a warm place or under a light.
You will need to compare the number of colonies that grow from each area. You can also note the differencesin the type of colonies.
-----Answer-----
 Hi Again Julianne
bacteria grow best at 35 degrees but will still grow at lower temperatures.  it just might take a bit longer.  If at home and you have a heated home keep the plates near a furnace room.  You can also keep them under a lamp.

Answer
 It is correct to keep the plates upside down.The object of incubating the plates this way is to keep the water off of the agar and the bacteria. You do not want the water rolling around on the colonies because it can transfer bacteria to your hands This water is from condensation.  When you look at the plates just pick up the bottom and don't turn it over. Then shake out the lid into the sink and replace the bottom.
 These dots are colonies.  Be very careful when examining the colonies and do not touch any of them.  Bacteria cannot "jump" off of the plates and most are harmless but you must assume that all are dangerous.  keep me informed as to the progress of your project.