Ch. 9 Controlling Microbial Growth Environment Study Guide
Basic Principles of Microbial Control (pp. 259–261)
1. Terminology of microbial control
a) Antisepsis, aseptic, degerming, disinfection, pasteurization, sanitization, sterilization
2. Action of microbial agents
a) Alteration of cell wall & cell membranes
b) Damage to proteins & DNA & RNA
c) Relative susceptibility to antimicrobial agents – most resistant to most susceptible microbes
The Selection of Microbial Control Methods (pp. 261–264)
1. Factors Affecting the Efficacy of Antimicrobial Methods
a) Germicide classification – high, intermediate & low level germicides and the microbes they
can kill
2. Biosafety Levels – BSL 1, 2, 3 & 4
Physical Methods of Microbial Control (pp. 264-271)
1. Moist heat – autoclaving (121C, 15psi, 15mins), pasteurization
2. Filtration – pore size of filters and the type of microbes they keep out.
3. Osmotic pressure – effect of salt & sugar in creating hypertonic solutions to control growth
4. Radiation – mechanism of UV radiation (prymidine dimerization)
Chemical Methods of Microbial Control (pp. 271–278) – know the general mechanism of action for
each (table 9.5/slide 53 on ppt)
1. Phenol & phenolics
2. Alcohols
3. Halogens – chlorine bleach
4. Oxidizing agents – ozone, hydrogen peroxide
5. Soaps & detergents
6. Aldehydes – glutaraldehyde, formalin
7. Enzymes
8. Antibiotics
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