Page 69 - MNU microbiology theoritical 2025
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General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025
1. Lag Phase
- After inoculation into fresh medium.
- The population remains temporarily unchanged.
- The cells may synthesize enzymes, proteins, RNA, etc., and increase in
.
metabolic activity
2. Exponential (log) Phase
- Cells divide at a constant rate due to abundant food, absence of competition
and of inhibiting factors such as toxic waste products
• The log phase is also the stage where bacteria are the most susceptible to the
action of disinfectants and common antibiotics that affect protein, DNA, and
cell-wall synthesis.
• During the initial phase of exponential growth cells produce primary
metabolites such as amino acids and nucleotides.
• Late log phase, secondary metabolites (antibiotics), depletion of nutrients and
buildup of waste products
General Microbiology & Immunology (PM 401) theoretical handbook Page 58
