Chapter 4: Microbial Growth - Culture Flashcards
1
Q
What is bacterial growth? (2)
A
- refers to increase in bacterial cell numbers
- not an increase in size of individual cells!
2
Q
How do most bacteria reproduce, and how? (3)
A
- binary fission
- the cell elongates and makes a copy of its DNA
- divides into two identical cells
3
Q
In lecture, what are 3 ways to replicate bacteria?
A
- transformation
- transduction
- conjugation (plasmids)
4
Q
Why is microbial growth exponential growth?
A
- Since bacteria divide by binary fission, the population of cells will double every generation
5
Q
What is generation time?
A
- time required for population to double
- varies greatly between different bacteria
6
Q
What is E. coli’s generation time?
A
- 20 min
7
Q
What is Mycobacterium tuberculosis’ generation time?
A
24 hours
8
Q
What process is used to grow bacteria in a lab?
A
- innoculation
9
Q
What is the definition of innoculation?
A
- introducing microbes into a medium to start a culture
10
Q
What is a culture?
A
- microbes growing in a medium
11
Q
What are two types of culture?
A
- batch
- continuous
12
Q
What is a batch culture? (3)
A
- closed system
- once started, no other nutrients is added
- bacteria stop growing when nutrients is used up
13
Q
What is a continuous culture? (4)
A
- open system
- nutrients continuously added
- wastes are continually removed
- supports indefinite growth
14
Q
Name the phases of growth in Batch culture (5)
A
- Lag phase
- Exponential phase (log phase)
- Stationary phase
- death phase
- Phase of prolonged decline
15
Q
What is the lag phase? (2)
A
- a period of adaptation
- cells adjust to new media and get ready to grow
16
Q
What is the exponential phase (log phase)? (3)
A
- period of maximal reproduction
- cell number increases exponentially
- used to calculate generation time
17
Q
What is the stationary phase? (3)
A
- cells have reached maximum population density
- nutrients have been used up, or wastes have accumulated
- no increase in cell number
- aka plateau phase
18
Q
What is the death phase? (2)
A
- toxic waste products have accumulated
- cells die at a uniform rate
19
Q
What is the phase of prolonged decline? (3)
A
- sometimes a small fraction of population survives the death phase
- may consume nutrients from dying cells
- selects for the strongest cells in the population
- this is an example of transformation
