Keeping It Clean (continued)
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3. Create a Lawn of "Bacteria"
a. Open the sterile swab; do not touch the cotton tip.
b. Put the swab into the simulated "Bacterial Suspension" to take a sample.
i. Gently press the swab against the inside of the test tube to remove any extra liquid and prevent drips.
c. Open the Petri dish just enough to insert the swab and rub the swab over the entire surface of the medium. Use care to
avoid tearing the surface of the medium.
d. Replace the Petri dish cover and set the swab aside in the contaminated tools area.
4. "Inoculate" Tube media
a. Open the sterile inoculating loop or swab.
b. Imagine your bacterial plate from step 4 has finished incubating and now contains a fresh lawn of bacteria on it.
c. Open the Petri dish just enough to insert the loop under the lid. Reach under the lid with the loop and make an indentation
in the middle of the medium to simulate picking up some bacteria from the surface of the plate.
d. Remove the loop and close the Petri dish.
e. Place the inoculating loop into the "bacterial suspension" in the test tube to simulate transferring the bacteria to the media
i. Stir the suspension with the inoculating loop and remove the loop.
ii. Place the loop in your contaminated tools area.
5. How aseptic were you?
a. Keeping gloves on, view all materials under the UV light. Be sure to look at your gloves, the Petri dish, the swab, the loop,
the test tube, and the surface of the agar.
b. In a Data Table (on the next page), make notes of where you see contamination.
Follow-up/Teaching Notes
1. In step 2, the Glo-Germ simulates the bacteria that we all have on our skin, clothes, and work surfaces. In a real lab, we trans-
fer these bacteria between each other and to objects in our environment without even noticing.
2. In Step 3, students are simulating the actions required to inoculate a media plate from a liquid culture of bacteria. In a real
situation, this plate would now be incubated overnight (or longer) and would grow a lawn of bacteria.
3. In step 4, students are simulating the actions required to 'pick' bacteria from an established plate of bacteria and transferring
it into a liquid medium. In a real lab, this media would be placed in an incubator on a shaker or under some sort of agitation to
aerate the culture as it grows.
Results:
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Location Describe the contamination
How do you think the contamination
could have been prevented?
Petri Dish
Swab(s)/Loop(s)
"Bacterial Suspension:
Tube surface
"Bacterial Suspension":
Contents
Agar surface
Work area
Used tools area
