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Microbiology > Chapter 6: Microbial Growth > Flashcards

Chapter 6: Microbial Growth Flashcards

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Biology 101 flashcards
1
Q

How do bacteria divide?

A

By binary fission

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2
Q

What does cell division require?

A

DNA replication: complete, exact copy of chromosome.

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3
Q

How does binary fission occur?

A
  • chromosomes attach to membrane
  • membrane growth: chromosomes move apart
  • septum formation: new membrane and wall material start growing through midsection of cell
  • formation of two cells: membrane and wall material deposited at the cell midsection divide the cytoplasm in two
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4
Q

Phases of growth

A
  • Lag phase
  • exponential (log) phase
  • stationary phase
  • death phase
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5
Q

Phases of growth: lag phase

A

Adjustment to new conditions, few cells, little or no growth.

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6
Q

Phases of growth: exponential (log) phase)

A

Logarithmic growth, most growth, live cells.

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7
Q

Phases of growth: stationary phase

A

Cells undergo changes to survive, live and dead cells, no growth.

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8
Q

Phases of growth: death phase

A

Cells begin to die.

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9
Q

Continuous culture: chemostat

A
  • concentration of limiting nutrient
  • continuous: addition of nutrients , removal of waste-products
  • cell number remains constant
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10
Q

Colony growth

A
  • mass of cells
  • on laboratory medium
  • not same as in natural environment
  • used to study characteristics of microorganisms
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11
Q

Biofilms

A
  • natural environment
  • complex mix of microorganisms
  • unique interactions and impact on other microorganisms
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12
Q

Classification by nutrition: heterotrophs

A

Different feeders. Organic compounds as source of carbon.

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13
Q

Classification by nutrition: autotrophs

A

Self-feeders. CO2 as source of carbon.

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14
Q

Classification by nutrition: chemotrophs

A

Chemical feeders. Derive both carbon and energy from organic compounds.

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15
Q

Classification by nutrition: phototrophs

A

Light feeders. Energy from light.

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16
Q

Example of a chemoautotroph

A

Methanogens

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17
Q

Physical requirements for microbial growth

A

Temperature
pH
Osmotic pressure

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18
Q

Chemical requirements of microbial growth

A

Carbon
Nitrogen, sulfur, and phosphorus
Trace elements
Oxygen

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19
Q

What are the direct methods to measure microbial growth?

A

Plate count
Filtration
Most probable number
Direct microscopic count

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20
Q

What are indirect methods of measuring microbial growth?

A

Turbidity
Metabolic activity
Dry weight

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21
Q

At what pH do most bacteria like to grow?

A

Between 6.5 and 7.5

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22
Q

At what temperature would a human pathogen likely grow? What type of microbe is it?

A

About 37 C, mesophile.

23
Q

What happens to a cell when placed in a hypotonic solution?

A

The cell will swell and possibly burst. A hypotonic solution has a greater concentration outside of the cell.

24
Q

What happens when a cell is placed in a hypertonic solution?

A

The cell will shrink. A hypertonic solution has a lower concentration outside of the cell.

25
Q

What happens when a cell is placed in an isotonic solution?

A

The cell will be in homeostasis. The concentration is the same inside and outside of the cell.

26
Q

How can bacteria be enumerated?

A 
Turbidity 
Direct cell count
Automated devices such as coulter counter 
Flow cytometer 
Real-time PCR
27
Q

How to check turbidity of bacteria?

A

Using a spectrophotometer. Measures the absorbance of light by cells in broth culture. The greater the turbidity, the larger the population size.

28
Q

Direct cell count method

A

Counts the total dead and live cells in a microscopic slide containing a pre measured grid.

29
Q

How does a coulter counter work?

A

Uses an electronic sensor to detect and count the number of cells.

30
Q

What is generation time?

A

The time required for a complete division cycle.

31
Q

Length of the generation time is a measure of

A

The growth rate

32
Q

What are used to define the numbers of bacteria after growth?

A

Exponentials

33
Q

Psychrophiles

A

An organism that grows best at about 15 degrees C, does not grow above 20 degrees C. Cold-loving microbe.

34
Q

Mesophiles

A

An organism that grows beaten about 10 degrees C and 50 degrees C. Moderate-temp-loving microbe
Best at about 37 C

35
Q

Thermophiles

A

An organism whose optimal growth temperature is between 50 degrees C and 60 degrees C, a heat-loving-microbe

36
Q

What is the most common type of microbe?

A

Mesophiles.

37
Q

Extreme or hyperthermophiles

A

Have an optimum growth temperature of 80 C or higher.

38
Q

Acidophiles

A

A bacteria that grows slow pH 4

39
Q

Plasmolysis

A

Loss of water from a cell in a hypertonic environment

40
Q

Halophile

A

An organism that grows in or can tolerate saline conditions.

41
Q

Plate count

A

Most frequently used method of measuring bacterial population
Inoculate plate with a sample and count number of colonies

42
Q

Filtration

A

Used to measure small quantities of bacteria

43
Q

Most probable number

A

Used mainly to measure bacteria that will not grow on solid medium
Dilute a sample repeatedly and inoculate several broth tubes for each dilution point
Count the number of positive tubes in each set

44
Q

Direct microscopic count

A

Stain is added to visualize bacteria

Cells are counts and multiplied by a factor to obtain concentration.

45
Q

Obligate anaerobes(strict)

A

Bacteria that cannot grow in the presence of oxygen

46
Q

Aerotolerant anaerobes

A

Cannot use oxygen for growth but can tolerate its presence.

47
Q

Facultative anaerobes

A

Can grow without oxygen but use oxygen if it is present

48
Q

Microaerophile

A

Requires oxygen to survive but requires environments containing lower levels of oxygen than are present in the atmosphere

49
Q

Alkalinophile

A

Prefers or is able to withstand an alkaline environment, pH above 9

50
Q

Strict aerobe (obligate)

A

Requires oxygen to grow

51
Q

What is quorum sensing?

A

The ability of bacteria in a biofilm to communicate with each other and coordinate their activities.

52
Q

The microbes in biofilms can work

A

Cooperatively to carry out complex tasks

53
Q

Phagocytosis

A

The ingestion of bacteria or other material by phagocytes and amoeba is protozoans

54
Q

Pinocytosis

A

The ingestion of liquid into a cell by the budding of small vesicles from the cell membrane

Microbiology (5 decks)

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