1. LECTURE: Physical Requirements of Bacteria
MICROBIOLOGY – ALCAMO
LECTURE:
Physical Requirements of Bacteria

2. Physical Requirements of Bacteria
In order to kill bacteria, you need to know what conditions they need to survive
Then if you take away what they need, death follows

3. 1. Temperature Each kind of MO has its own best temp.
OK a little below or above
= Optimum Temp, Minimum and Maximum
Reason: Enzymes only
react at specific
narrow temperature range

4. Temperature Classifications:
Psychrophiles: C (0 - 70F)
Mesophiles: C ( F)
Pathogens: 37C (98.6F)
Thermophiles: C ( F)

5. 2. pH Refers to Acid/Base Balance Acid = Free H+, Base = Free OH-
Scale:
Acid = 1 - 6
Neutral = 7
Base =
Most MO grow best 6.4 – 7.5

6. 3. Water All organisms need water as solvent for chemical reactions
If water is drawn from cell, it dries out
1 – 2% ions (salt) dries out most MO

7. 4. Oxygen
Oxygen completes electrical circuit for respiration reactions
“O” is last receiver of H+ = H2O
Most MO need air = Aerobic
Some MO have other enzyme system
No Air = Anaerobic
Some can be both = Facultative
Very low O2 requirement = microaerophilic

8. 5. Light Needed if photosynthetic (rare)
Absence of light needed by most MO