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Micro Physiology > Module 3 - Microbial Growth > Flashcards

Module 3 - Microbial Growth Flashcards

1
Q

What are the four basic phases of bacterial growth?

A
  • Lag phase
  • Log phase
  • Stationary phase
  • Death phase
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2
Q

What occurs during the lag phase of bacterial growth?

A

Period of little to no cell division; cells do not immediately reproduce but undergo intense metabolic activity

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3
Q

What is another name for the log phase in bacterial growth?

A

Exponential growth phase

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4
Q

What characterizes the log phase of bacterial growth?

A

Cells divide actively, and generation time reaches a constant minimum

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5
Q

What happens during the stationary phase of bacterial growth?

A

Growth rate slows, number of deaths balances new cells, and population stabilizes

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6
Q

What defines the death phase in bacterial growth?

A

Number of deaths exceeds new cells, leading to a decline until the population diminishes or dies out

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7
Q

What is a batch culture?

A

Method of growing microorganisms in a closed system with nutrients provided only at the start

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8
Q

What is a continuous culture?

A

Also known as open system; continuously supplies nutrients and removes waste products

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9
Q

How do bacterial cells reproduce?

A

By binary fission, where one cell divides into two

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10
Q

What is the basic equation for exponential bacterial growth?

A

N = N₀ * 2^n

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11
Q

What does each symbol represent in the equation N = N₀ * 2^n?

A
  • N: Final number of cells
  • N₀: Initial number of cells
  • n: Number of generations
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12
Q

How can generation time be calculated?

A

Using a semilogarithmic plot where the slope represents the growth rate (k)

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13
Q

What is the division rate (v) in microbial growth?

A

Reciprocal of the generation time; indicates how many generations occur per unit of time

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14
Q

What is the optimum temperature for most pathogenic bacteria?

A

37 degrees Celsius

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15
Q

What are psychrophiles?

A

Cold-loving microbes that grow within a temperature range of 0–20 degrees Celsius

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16
Q

What are mesophiles?

A

Moderate temperature-loving microbes that grow between 25 and 40 degrees Celsius

17
Q

What are thermophiles?

A

Heat-loving microbes that can grow at temperatures between 55–80 degrees Celsius

18
Q

What role do heat shock proteins (HSPs) play in stress response?

A

Assist microbes in handling heat stress by refolding damaged proteins

19
Q

What are aerobic bacteria?

A

Bacteria that require oxygen for growth

20
Q

What are obligate aerobes?

A

Bacteria that can grow only in the presence of oxygen

21
Q

What are facultative aerobes?

A

Bacteria that can grow with or without oxygen; most pathogenic bacteria belong to this group

22
Q

What are obligate anaerobes?

A

Bacteria that can grow only in the absence of oxygen

23
Q

What is the pH range for most pathogenic bacteria?

A

Between pH 7.2 and 7.6

24
Q

What is osmotic pressure in relation to microbial growth?

A

Factors such as osmotic pressure and salt concentration affect the growth of bacteria

25
Q

What are osmophilic bacteria?

A

Organisms requiring high osmotic pressures

26
Q

What happens to bacteria in a hypertonic solution?

A

Causes osmotic withdrawal of water, leading to plasmolysis

27
Q

What are barophiles?

A

Microbes that have adapted to high pressures, such as those found at the ocean’s bottom

28
Q

What is the effect of radiation on cells?

A

Causes damage to DNA, leading to mutations and cell destruction

29
Q

How do bacterial endospores respond to ionizing radiation?

A

They are extremely resistant to the harmful effects

30
Q

What types of radiation cause mutations and destruction of the cell’s DNA?

A

X-rays and gamma rays

These types of ionizing radiation can lead to significant cellular damage.

31
Q

Which type of bacterial cells are extremely resistant to the harmful effects of ionizing radiation?

A

Bacterial endospores

Endospores can withstand extreme environmental conditions, including radiation.

32
Q

What were vegetative cells thought to be in relation to ionizing radiation?

A

Quite susceptible

Vegetative cells are the active form of bacteria, as opposed to dormant endospores.

33
Q

What is the purpose of DNA repair mechanisms in microorganisms?

A

To repair damage caused by radiation

These mechanisms help maintain cellular integrity and functionality.

34
Q

Name one DNA repair mechanism used by microorganisms.

A

Photoreactivation

This mechanism involves the direct reversal of DNA damage caused by UV light.

35
Q

What is another DNA repair mechanism besides photoreactivation?

A

Excision repair

This mechanism removes damaged DNA and replaces it with the correct sequence.

36
Q

What is the SOS response in microorganisms?

A

A DNA repair mechanism activated in response to extensive DNA damage

This mechanism allows cells to repair DNA damage that might otherwise lead to cell death.

Micro Physiology (3 decks)

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