1. Observe and record provided experiment results:
Lab 25 Goals and Objectives:
Observe and record provided experiment results:
Exercise 30: Water Activity and Osmotic Pressure
Exercise 32: Effects of Lysozyme on Bacterial Cells
FOUR GROUPS for all activities:
Exercise 31: Lethal Effect of UV Light
Do your assigned organism and times (see assignment)
Completely cover plate with organism: swab three times
Draw a line to indicate boundary of the card
Lid off, agar side up under lamp (unless assigned “with lid”)
Exercise 61: Temperature Lethal Effects (Do this LAST!!!)
Each group do all three organisms at one temperature (assigned)
Omit 60°C (100°C needs boiling water)
Plate control BEFORE heating!!! Spread plate using pipettes
Thermometer not necessary: allow 3 min to equilibrate
Observe and record provided results
**Bring favorite disinfectant/antimicrobial to next lab to test!

2. Exercise 30: Water Activity and Osmotic Pressure
Observe and record provided experiment results
Determine which organism is:
the halophile (requires 15-30% NaCl)
halotolerant (can survive up to 11% NaCl)
not tolerant of NaCl (typically less than 6% NaCl)

3. Exercise 32: Effects of Lysozyme on Bacterial Cells
Observe and record provided experiment results
Lysozyme = enzyme produced in body secretions, degrades bonds holding the lattice of peptidoglycan together
*Outer membrane can prevent access of lysozyme to peptidoglycan
*Teichoic acids can prevent degradation

4. Draw line on plate to indicate boundary of card
Cover half with paper card
Plates agar side up, no lid, cover half with paper card
UV Exposed side
Control
(was covered)
Exercise 31: Lethal Effects of UV Light

5. Exercise 61: Temperature Lethal Effects (Do this LAST!!!)
No thermometer, just set in bath for three minutes before you start timing
Each group assigned one temperature
One person in group per organism to time and plate when appropriate
Staphylococcus aureus
Serratia marcescens
Bacillus subtilis
***Mix tube WELL before plating but keep tube in bath!!!
Figure 61.1

6. **Bring favorite disinfectant/antimicrobial to next lab to test!
Lab 25 Goals and Objectives:
Observe and record provided experiment results:
Exercise 30: Water Activity and Osmotic Pressure
Exercise 32: Effects of Lysozyme on Bacterial Cells
FOUR GROUPS for all activities:
Exercise 31: Lethal Effect of UV Light
Do your assigned organism and times (see assignment)
Completely cover plate with organism: swab three times
Draw a line to indicate boundary of the card
Lid off, agar side up under lamp (unless assigned “with lid”)
Exercise 61: Temperature Lethal Effects (Do this LAST!!!)
Each group do all three organisms at one temperature (assigned)
Omit 60°C (100°C needs boiling water)
Plate control BEFORE heating!!! Spread plate using pipettes
Thermometer not necessary: allow 3 min to equilibrate
Observe and record provided results
**Bring favorite disinfectant/antimicrobial to next lab to test!