EXPERIMENT


1/13/10
We bought our materials today.
6 petri dishes
6 long cotton swabs
distilled water
2 nutrient agar packets
gloves



1/14/10
We poured 300 ml of distilled water and two agar packets into a pan to boil and stirred continuously. After dissolving, we poured 30 ml of the solution in each petri dish. We then let it sit for 8 hours so it will harden. Here is a picture of a prepared petri dish:


We then started the experiment. I took off one glove for my mom to swab my hand and gently wiped it on the petri dish. She also swabbed my mouth and did the same. Then I swabbed the cat's paw and mouth. It was easier than I thought. The dog was the hard one.


I took my samples home and put them in a homemade incubator. I poked small holes in it and cut a hole in the front. I put a small digital thermometer in the box to check the temperature. I then put my box in front of a heater to keep the samples arount 97-100 degrees. I plan to check the samples every 48 hours. Here are some pictures of the incubator.



CONTROLS
When doing an experiment, controls are helpful so you know what caused the change. In my experiment, the controls were temperature, amount of agar solution, and the amount of time. This means that all the samples were kept at the same temperature, had the same amount of agar solution, and I checked each sample at 6:00 pm every 48 hours. This let me know that the amount of bacteria grown was caused by the type of sample I took (dog, cat, or human).