Download April Davis` Science Class

Bacteria Plating Lab
Overview and Purpose:
Did you know that even though you may wash your hands frequently, your skin
picks up bacteria from the objects you touch? You cannot see or feel these
tiny organisms, but they are there.
In this investigation you will:
-
Sample bacteria in your environment
Sample bacteria on your hands
Problem:
Do you pick up bacteria from your environment?
Materials:
Covered petri dishes with sterile nutrient agar
Marker
Tape
Everyday object
Sterile cotton swab
Hand lens
Gloves
Procedure:
1. Get an agar petri dish. DO NOT OPEN IT YET!
2. You can now either test your hands to check for bacteria or you can test
another object.
3. If testing HANDS:
a. Remove the lid from the dish. GENTLY press the tips of two
fingers onto the surface of the agar.
b. Close the lid immediately. Tape the dish closed.
c. Mark the tape with your name and the date. Wash your hands.
4. If testing an object:
a. Choose a small object you use every day, such as a coin or an
eraser. Remove the lid from the dish.
b. Swipe the object across the agar. You can also use a sterile swab
to rub on the object and then swipe the swab across the agar.
Close the lid immediately.
c. Tape and mark the dish with the object used, your initials, and
the date.
5. If testing an area with a swab, such as the spout of the water fountain:
a. Swab the area you want to test with the cotton swab.
b. Remove the lid from your petri dish, and swipe the swab across the
agar.
c. Close the lid immediately, tape it, and mark the tape with the
object you swabbed, your initials, and the date.
Complete the following: DO NOT OPEN THE DISH
1. What did you swab onto you agar?
2. Write a description of what you see on the plate.
3. Observe the amounts of bacterial growth in each dish.
any fuzzy growths?
D0 you notice
4. Why is it necessary for the agar to be sterile?
5. What function does the agar serve?
6. Why is it important to keep the dishes covered?
7. Why is it important to use separate petri dishes for each sample?