1. Effecting factors of microorganism growth –radiation (ultraviolet, UV)
chapter 24, page 170
Microorganisms:
bacteria: Escherichia coli,
Medium:
tryptic soy agar (TSA) for E. coli
All microorganisms are incubated at 37 ℃ before experiment.
UV light: inside laminar flow hood.

2. Procedures Each group takes their microbial culture
Streak the bacterial culture onto TSA plates (two bacteria on one TSA plate)
Each group should has 10 TSA
Separate the plates into 5 groups, each group has two microorganism (group A, B, C, D, E)

3. Turn on the laminar hood
Place group A plates on test tube racks to get close to the UV light
Place group B plates on the bottom surface of the laminar hood
Measure distance between the plates and the UV light
Open the plates
Pull down the curtain (MUST)
Turn on UV light
UV exposure for 10 min
Turn off UV light
Close and take plates out

4. Place group D plates on the same place of group A
Place group E plates on the same place of group B
Open the plates
Pull down the curtain (MUST)
Turn on UV light
UV exposure for 30 min
Turn off UV light
Close and take out plates
Group C is the control. Do NOT expose group C plates to UV light.
Incubate plates 37 ℃ (E. coli and B. subtilis)
Observe the growth of bacteria on the next day.

5. Group on duty on another test 畫後再照 (streak, incubate, then UV)
Streak the bacteria onto one TSA plate in advance
Place on the positions of A and B (totally two sets)
UV light for 10 min
Turn off UV
Streak on new plates

6. Effecting factors of microorganism reduction –heat chapter 24, page 170
Moisture heat
Water (water bath) (1-6 group)
Steam
Dry heat
Oven (7-11 group)

7. Microorganism
Non spore producer
Escherichia coli

8. Temperature and time Temperature Time Heat source 80 and 60℃
10 and 20 min
Heat source
Water bath (wet heat)
Oven (dry heat)

9. 4 combination 80℃ – 10 min, 80℃ -20 min, 60℃ -10min, 60℃ -20 min
Each treatment has one heat source and one bacteria
Each group has 8 plates
Place the tubes containing bacteria culture into water bath and oven

10. Cool down the tubes with running tap water
Shake the tubes
Streak the bacteria culture onto plates
Incubate plates at 37℃ for 24 hours
Observe on the next day

11. Group on duty
Place the bacterial culture into whole milk instead of phosphate buffer
place the tubes into water bath
80℃ – 10 min, 80℃ -20 min, 60℃ -10min, 60℃ -20 min
Cool down
Streak onto plates
Compare organic matters vs. pure chemical buffer