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4. With a hot pad protecting your hands, remove the agar bottle from the microwave. Use caution when removing the bottle from the microwave as it will be HOT! 5. Gently swirl the bottle a final time to mix the solution. 6. Pour the agar solution into the bottom half of four Petri dishes. Use the agar sparingly. You only need enough to coat the bottom of the petri dish. Note: Approximately 5 mL should be enough agar to cover the entire bottom of the dish. If not, continue to add agar in approximately 1 mL increments until the bottom of the petri dish is completely covered. The agar should be only 1 or 2 millimeters deep. If too much agar is poured, there will be no space under the cover for microbial growth. 7. Place the lids onto the dishes slightly off-center to create a small space to allow condensation to evaporate and allow the agar to solidify undisturbed. This should take approximately 30 – 60 minutes. If you will not be using the dishes immediately, you can store them upside down in the refrigerator after they have fully gelled. Remove them from the refrigerator, and allow them to sit at room temperature for at least 1 hour prior to use. 8. Use a permanent marker to label the bottom of the plates (the agar side) as #1, #2, #3, and #4. PREPARE THE YEAST SOLUTION 1. Measure 230 mL of warm water (~38 C/100 F) into a 250 mL beaker. ̊ ̊
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2. Add 1 tsp. of sugar and the yeast packet to the beaker of warm water. Gently stir the solution to dissolve the ingredients. The solution should begin to foam/froth after a few minutes. COLLECT HAND BACTERIA 1. Put a disposable glove on your non-dominant hand (i.e., your left hand if you are right-handed; your right hand if you are left- handed). 2. Use a disposable transfer pipette to add 8 – 10 drops of distilled water to the palm of your gloved hand. Rub your hands together to spread the water over the surface of your ungloved hand. Remove and dispose of the glove. 3. Wipe the surface of your ungloved hand with the water on it with a sterile cotton swab. Gently rub the cotton swab on the surface of nutrient agar plate #1. Do not press too hard, or you will damage the agar. Put the lid on the plate and discard the cotton swab.
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  • Fall '19
  • Agar plate, Petri dish, Agar

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