Chapter_7_Bacterial and Archaeal Growth Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Describe the three phases of a bacterial cell cycle. The overlapping of cytokinesis and chromosome partitioning could potentially create problems for a cell during the cell cycle. What mechanisms does the cell use to prevent problems?

A
  • 3 phases of the cell cycle are: growth phase, chromosome replication, cytokinesis
    The cell uses the divisome mechanism at the right time to avoid premature cytokinesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What elements of the Sulfolobus spp. cell cycle are similar to the bacterial cell cycle? What elements are similar to the eukaryotic cell cycle?

A
  • Proteins segA and segB, and cytokinesis are similar to the bacterial cell cycle
    Cell cycle phases G1, S, G2, dna replication machinery, segA, segB, and histone like proteins are similar to the eukaryotic cell cycle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define microbial growth.

A
  • The increase in # of cells in a microbial population
  • Measured in terms of population size over time
    Uses a growth curve
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the phases of the growth curve and discuss the causes of each.

A
  • Lag phase: cells adapt to new conditions and synthesize necessary components
  • Log phase: cells divide exponentially
  • Stationary phase: growth slows due to nutrient depletion or waste accumulation
  • Death phase: cells die at a constant rate
    Long term stationary phase: population levels remains constant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why must k and g be calculated from exponential phase measurements?

A
  • K is growth rate constant
  • G is generation time
  • Growth is constant during exponential phase
    There is an accurate doubling time during exponential phase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why would vigorously growing cells have a shorter lag phase than those that have been stored in a refrigerator when inoculated into fresh culture medium?

A
  • Vigorously growing cells are already adapted to the environmental conditions
    Cells in a refrigerator need to adapt to environment in order to start growing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do microorganisms adapt to hypotonic and hypertonic environments?

A
  • To adapt to hypotonic environments they need to release solutes from inside the cell through mechanosensitive channels
    In hypertonic environments they have to increase solute concentration inside the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are halophiles and why do they require sodium and potassium ions?

A
  • Halophiles are microorganisms that thrive in high salt concentrations
  • They need Na+ and K+ to balance osmotic pressure between their cytoplasm and high salt external environment
    Salt in: high K+ in cytoplasm, high Na+ in external environment
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define water activity. Why is it difficult for microorganisms to grow at low aw values?

A
  • Water activity is the availability of water for microbial growth
    Difficult for microbes to survive w/o water due to osmotic stress, loss of proteins etc…
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why does the growth rate rise with increasing temperature and then fall again at higher temperatures?

A
  • Increased enzyme activity, membrane fluidity, metabolic rates with rising temp
    Enzyme denaturation, instability, dna damage with too high temp
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Identify environments where you could find microbes considered psychrophilic, psychrotolerant, mesophilic, thermophilic, and hyperthermophilic

A
  • Psychrophiles = 0-20C
  • Psychrotrophs = 0-35C
  • Mesophiles = 20-45C
  • Thermophiles = 45-80C
    Hyperthermophiles = 85-113C
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the five types of O2 relationships seen in microorganisms.

A
  • Obligate aerobe = needs o2
  • Microaerophile = needs 2-10% o2
  • Facultative anaerobe = doesn’t need o2 but grows better with it
  • Aerotolerant anaerobes = grow w or w/o o2
    Strict anaerobe = killed w o2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where would you expect to find barotolerant and piezophilic microbes? Explain your answer

A
  • Barotoletant: moderate to high pressure because they can survive but are not dependent on pressure for growth
    Barophilic: high pressure because they need it for optimal growth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is a biofilm? List two ways life in a biofilm is advantageous for microbes.

A
  • Complex community of microorganisms attached to a surface with a self produced extracellular polymeric substances (EPS)
    Advantageous because eps protects from environmental stresses and eps is able to trap nutrients
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is quorum sensing? Describe how it occurs, and briefly discuss its importance to microorganisms.

A
  • Cell to cell communication
  • Microbes produce and release small signaling molecules
    Important for coordinating group behaviours and survival advantages
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When using direct cell counts to follow the growth of a culture, it may be difficult to tell when the culture enters the death phase. Why?

A

Direct counting methods cannot differentiate between dead and live cells

17
Q

Why are plate count results expressed as colony forming units?

A
  • Colony can originate from one or many cells
  • Not all cells are viable
    Variable growth conditions