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MBIO1010 > Chapter 5: Microbial Growth > Flashcards

Chapter 5: Microbial Growth Flashcards

1
Q

Growth

A

Measured as an increase in the number of cells

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2
Q

Binary fission

A

Cell division following enlargement of a cell to twice its minimum size

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3
Q

Generation time

A

Time required for microbial cells to double in number

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4
Q

Each daughter cell receives during cell division

A

A chromosome and sufficient copies of all other cell constituents to exist as an independent cell

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5
Q

What occurs simultaneously in bacteria and archaea?

A

Growth in cell size, chromosome replication, and septum formation

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6
Q

Is there mitosis in bacteria and archaea?

A

No

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7
Q

Generation time is dependent on

A

Growth medium and incubation conditions: carbon source, pH, temperature, etc.

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8
Q

Exponential growth

A

Growth of a microbial population in which cell number double at a constant and specific time interval

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9
Q

What kind of curve does exponential growth create?

A

One that has a slope that increases continuously

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10
Q

Growth rate (k)

A

Rate of increase in population number or biomass.

Expressed in bacteria and archaea as number of doublings per hour

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11
Q

Generation time

A

Time it takes for each to cell to become 2 cells

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12
Q

Specific growth rate

A

Fastest growth rate in the best medium and optimal temperatures

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13
Q

Batch culture

A

Closed-system microbial culture of fixed volume

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14
Q

Lag phase

A

Interval between inoculation of a culture and beginning of growth

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15
Q

Exponential phase

A

Cells in this phase are typically in the healthiest state

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16
Q

Stationary phase

A

Cells metabolically active, but growth rate of population is zero

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17
Q

Why is growth rate in stationary phase zero?

A

Either an essential nutrient is use up, or waste product of the organism accumulates in the medium

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18
Q

Death phase

A

If incubation continues after cells reach stationary phase, the cells will eventually die

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19
Q

Do all bacteria die in the death phase?

A

Some bacteria form spores/cysts or dormant stage that allow a significant proportion of cells to survive for a long time

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20
Q

Continuous culture

A

Open-system microbial culture of fixed volume

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21
Q

Chemostat

A

Most common type of continuous culture device

Both growth rate and population density of culture can be controlled independently and simultaneously

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22
Q

Dilution rate

A

Rate at which fresh medium is pumped in and spent medium is pumped out

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23
Q

Concentration of limiting nutrient controls

A

Population size and the growth rate

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24
Q

How are microbial cells counted by direct microscopic observations?

A

Petroff-Hausser counting chamber

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25
Q

Petroff-Hausser counting chamber

A

Each square corresponds to a calibrated volume

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26
Q

Limitations of microscopic counts

A
  • Cannot distinguish between live and dead cells without special stains
  • Small cells can be overlooked
  • Precision is difficult to achieve
  • Phase-contrast microscope required if a stain is not used
  • Low density cell suspensions are hard to count
  • Motile cells need to be immobilized
  • Debris in sample can be mistaken for cells
  • Brownian motion, some forms clumps
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27
Q

Flow cytometer

A

Second method for counting cells in liquid samples

Uses laser beams, fluorescent dyes, and electronics

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28
Q

Viable cell counts (plate counts)

A

Measurement of only living cells capable of growing to form a population

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29
Q

Methods of plate counts

A

Spread-plate method

Pour-plate method

30
Q

Viable count issues

A
  • Preparation and incubation time
  • Unreliable on counts of natural samples
  • Culture media and growth conditions can’t grow every microbe
31
Q

The great plate anomaly

A

Direct microscope counts of natural sample reveal far more organisms than those recoverable on plates

32
Q

How much microbial diversity is culturable?

A

1-10%

33
Q

What supports the great plate anomaly?

A

Microscope methods count dead cells, whereas viable methods do not
Different organisms may have vastly different requirements for growth

34
Q

Turbidity measurements

A

Indirect, rapid, and useful methods of measuring microbial growth

35
Q

How is turbidity measured?

A

With a spectrophotometer

36
Q

What is turbidity measured in?

A

Optical density

37
Q

Why is turbidity measured in optical density?

A

Bacteria behave like small particles and absorb and scatter light

38
Q

The larger the number of particles…

A

The greater the absorbance and the lower the light transmission to the photocell

39
Q

Does absorbance distinguish cells?

A

No it can’t tell live cells from dead cell or if it’s chemical particles

40
Q

Does turbidity require a stain?

A

No they do not disturb the sample

41
Q

How is direct cell related to turbidity?

A

A standard curve must first be established to another counting method

42
Q

What other counting methods are there?

A

Viable cell count
Weight of biomass produced
Measuring other parts of the cell which are proportional the the whole mass of cells

43
Q

Issues with optical density

A
  • Has a finite linear range of measurement
  • Only works if the cells are evenly distributed throughout the medium
  • Cuvette must not have scratches
  • Culture may need to be diluted when the cells are at a very high density
44
Q

Cardinal temperature

A

Minimum, optimum, and maximum temperatures at which an organism grows

45
Q

Psychrophile

A

Low temperature

46
Q

Mesophile

A

Midrange temperature

47
Q

Thermophile

A

High temperature

48
Q

Hyperthermophile

A

Very high temperature

49
Q

Where are mesophiles found?

A

In warm-blooded animals, terrestrial and aquatic environments, temperate and tropical latitudes

50
Q

Extremophiles

A

Organisms that grow under very hot or very cold conditions

51
Q

Psychrophile temperature optima

A

Less than 20 degrees celsius

52
Q

Psychophile environments

A

Permanently cold environments: deep oceans, Arctic and Antarctic environments

53
Q

Psychotolerant

A

Organisms that can grow at 0 degrees celsius but have optima of 20-40 degrees celsius

54
Q

Molecular adaptations that support psychrophily

A

Production of enzymes that function optimally in the cold

Modified cytoplasmic membranes - high unsaturated fatty acid content

55
Q

What life forms exist at above 65 degrees celsius?

A

Prokaryotes - chemorganotrophic and chemolithotrophic

56
Q

What is the upper limit temperature of phototrophy?

A

70 degrees celsius

57
Q

Thermophile optimal temperature

A

45-80 degrees celsius

58
Q

Hyperthermophile optimal temperature

A

Greater than 80 degrees celsius

59
Q

Hyperthermophile environments

A

Boiling hot springs and seafloor hydrothermal vents

60
Q

Methanopyrus kandleri

A

Archaeon that can grow at 122 degrees celsius

61
Q

Molecular adaptations to thermophily

A

Specific modifications provide thermal stability to enzymes and proteins
Modifications in cytoplasmic membranes to ensure stability

62
Q

Bacteria have what to survive high temperatures

A

Lipids rich in saturated fatty acids

63
Q

Archaea have what to survive high temperatures

A

Lipid monolayer rather than bilayer

64
Q

What produces enzymes widely used in industrial microbiology?

A

Hyperthermophiles

65
Q

Taq polymerase

A

Used to automate the repetitive steps in the polymerase chain reaction technique

66
Q

Hydrolytic enzymes

A

Proteases, cellulases, lipases

67
Q

True/false: enzymes of thermophiles are more stable and tend to have higher activity than mesophilic counterparts

A

True

68
Q

What are the upper temperature limits for life?

A

Suggested at 140-150 degrees celsius

69
Q

What are the closest descendants of ancient microbes?

A

Hyperthermophiles

70
Q

What supports the theory that hyperthermophiles are the closest descendants?

A
  • Are found on the deepest, shortest branches of phylogenetic tree
  • Oxidation of H2 is common to many hyperthermophiles and may have been the first energy-yielding metabolism

MBIO1010 (13 decks)

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