1. FOUR GROUPS for all activities:
Lab 25 Goals and Objectives:
FOUR GROUPS for all activities:
Exercise 30: Water Activity and Osmotic Pressure
Observe and record provided experiment results
Exercise 31: Lethal Effect of UV Light
Each group set up one organism (assigned) at all nine pHs
pH 4, 6, and 11 added to activity
Exercise 32: Effect of lysozyme on Bacterial cells
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 tubes!!! Spread plate using pipettes
Thermometer not necessary: allow 3 min to equilibrate

2. Exercise 31: Lethal Effect of UV Light
Read results
Exercise 31: Lethal Effect of UV Light
Do your assigned organism and times
Completely cover plate with organism: swab 3 times
Draw a line to indicate the boundary of
the card
Lid off, agar side up under the lamp
(unless assigned “with lid)
UV Exposed side
Control
(was covered)
Cover half with paper card

3. 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)
Exercise 32: Effects of Lysozyme on Bacterial Cells
Observe and record provided results

4. Exercise 62: 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 62.1