Lecture 7 Flashcards
What are the four phases of microbial growth?
- Lag phase (low log(#))
- Exponential (Log) phase
- Stationary phase (high log(#))
- Death phase (decreasing log(#))
When is penicillin effective according to the microbial growth curve phases?
During the log phase, as the rapid division of the cells make them highly susceptible to the cell wall inhibition of penicillin.
When are lysozymes effective according to the microbial growth curve phases?
During the log phase, as the rapid division of the cell walls make them highly suscpetable to the peptidoglycan inhibition of lysozymes.
What is bacterial generation time?
Doubling time of bacterial population
What is the equation of bacterial generation time?
Nt = N0 * 2^n
Optimal temperature conditions:
- Psychrophiles < 15C
- Facultative psychrophiles (psychrotrophs) 20-30C
- Mesophiles 20-40C
- Thermophiles 55-65C
Optimal water activity conditions:
- Hypotonic: aw = 1
- Isotonic: aw = 0.98
- Hypertonic (salt lakes): aw = 0.75
What are the two types of bacteria that survive hypertonic water activity?
- Osmotolerant: grows in low aw
- Halophiles: requires a low aw
Optimal pH conditions:
Acidophiles: 1.0 - 5.5
Neutrophiles: 5.5-8.0
Alkalophiles: 8.5-11.5
What are the two types of bacteria that survive high pressure environments?
Barotolerant: can grow > 1 atm
Barophilic: prefers to grow at > 1 atm
What are different bacteria’s relationship with oxygen?
Obligate aerobe: must have O2
Facultative anaerobes: can live without O2 but prefer O2
Aerotolerate anaerobes: with or without O2
Obligate anaerobe: only without O2
Microaerophiles: require a specific amount of O2
How are colonies measured?
Colony Forming Unit (CFU)
Why can H. pylori survive an acidic environment as a neutrophile.
It is able to produce urease which elevates the pH of its environment in order to be a more neutral range.
