Bacteria Count ResearchBacteria Count Research
by Jasperuun Virus and Mariesles
Dr. Patrick Shiel works in the Ag. Science Department at the University of Idaho. He volunteered to come to our class to help us learn about bacteria. We learned a lot. Thank you, Dr. Shiel, for coming to our classroom!
We learned that there are many kinds of bacteria. Most of them are good. Here are some of the jobs bacteria do. They volunteer their time...they do not get paid!
Digest our food
Give off oxygen
Recycle waste (sewage, compost, etc.)
Bacteria on the skin keep disease-causing microbes away by using the food and space the invaders might want.
Some bacteria stick close to plant roots and help them take up nutrients from the soil.
But bacteria also spoil food, cause smelly socks and shoes, and cause diseases like the plague, strep throat, and e. coli.
In our classroom, Dr. Shiel helped us grow bacteria. He brought petri dishes, sterile swabs and sterile containers of water. Here is what we did:
First, we brainstormed a list of places to test for bacteria. For example: cold water from the drinking fountain, handles on the drinking fountains and sink faucets, computer keys, door handle, light switch, a sixth grader's earwax, a pencil, etc.
We made guesses (hypotheses) about which places would contain the most bacteria. We thought places we touched often would have the most bacteria, like the computer keyboard or the doorknob.
We had several control dishes. Into these dishes, we poured sterile water and closed them immediately.
Then we each choose a place to test.
We took a sterile Q-tip and swabbed our test site.
We put the Q-tip in the sterile water container and stirred it around.
We poured the water
into a sterile petri dish which contained agar, a nutrient which helps bacteria grow.
We closed the dish and labeled it.
We left the dishes on the counter in our room for a few days and watched the microorganisms.
Some of the organisms grew so fast that we had to put the dishes into the refrigerator to slow the growth down. The room began to smell and some of us got headaches from the mold. (In Dr. Shiel's lab, he grows bacteria under a hood that filters smells and particles out of the room.)
We looked carefully at our dishes and drew pictures of what we saw. We counted the number of colonies of bacteria and the types of colonies. Some dishes had mold and fungus growing on them. The bacteria were slimey and the mold was fuzzy.
We recorded our counts onto a spreadsheet. Click here if you want to see the results.
When we were done, Dr. Shiel took the dishes back to his lab to autoclave them (destroy the bacteria).
Here is what we found:
We left two dishes open and exposed to the air. Surprisingly, one of those produced 218 different colonies of bacteria.
Evanitis' cough and Brian Tumor's earwax produced the largest number of bacterial colonies (500+).
The outdoor slide, air, and toilet seat from the girls' bathroom produced the most types of bacterial colonies (5-6).
The door handle and pencils from the room produced the least number and types of bacteria. Maybe the metal and wood was not a good place for bacteria to grow.
Image
Petri dish. 2 March 2002. http://www.lbusd.k12.ca.us/robinson/Graphics/Bacteria.jpg