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Microbiology > Microbial Growth > Flashcards

Microbial Growth Flashcards

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Biology 101 flashcards
1
Q

Which elements are essential for microorganisms? (7)

A

H, C, N, O, P, S, Se

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2
Q

What needs to be done before the incorporation of most nutrients into cellular material?

A

Slight modification

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3
Q

___ are required in large amounts. Ex.

A

Macronutrients. Ex: Carbo, nitrogen, hydrogen, oxygen, phosphorous, sulfur, potassium, magnesium, calcium, sodium.

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4
Q

___ are required in trace amounts. Ex.

A

Micronutrients. Ex: iron, manganese, cobalt, copper.

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5
Q

What are growth factors?

A

Vitamins, amino acids, purines, pyrimidines and other organic molecules that the microorganism needs for growth but can’t synthesise by itself.

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6
Q

Can by-product or waste of microorganism be growth factors?

A

Yes

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7
Q

Example of growth factors.

A

Vitamin K, Biotin, p-amino benzoic acid, folic acid, riboflavin, lipoid acid, thiamine.

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8
Q

What is the growth of the population?

A

The increase number of cells or biomass

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9
Q

How do most prokaryotes multiply?

A

Binary fission

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10
Q

What are the 3 steps of binary fission?

A
  1. Cell elongation
  2. Septum formation
  3. Completion of septum, formation of walls, cell separation.
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11
Q

What does each daughter cell receive to exist ad an independent cell?

A

The cell receives:

  • one copy of the chromosome
  • ribosomes
  • macromolecules
  • other molecules
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12
Q

What is the generation time of e.coli?

A

20 minutes

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13
Q

What does cell division require?

A

It requires:

  • synthesis of the news cell wall material
  • its destruction by autolysins
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14
Q

What allows peptidoglycan subunit to be exported across the cytoplasmic membrane?

A

Bactoprenol

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15
Q

Where do autolysins create some gaps in the peptidoglycan? What does this allow?

A
  • At the division ring (FtsZ ring)

- this allows the rearrangement of the peptidoglycan and synthesis of the new cell wall.

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16
Q

What are wall bands?

A

Scars between old and new peptidoglycan?

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17
Q

What type of medium is MacConkey medium?

A

Selective

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18
Q

Bile salts inhibit growth of ___ and are permissive for ___/___ pathogens

A
  • gram +

- gram - / enteric

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19
Q

It differentiates between lactose ___ (pink) and lactose ___ (colourless)

A
  • fermenters

- non-fermenters

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20
Q

With bile precipitate, E. coli forms ___ colonies.

It is lactose ___ .

A
  • dark pink

- positive

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21
Q

What coloraturas are lactose negative?

A

colourless

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22
Q

Lactose -> __ + __

A

glucose + galactose

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23
Q

Glucose –> ___ –> ___(lactic acid, reduce pH)

A
  • glycolytic pathway

- fermentation: lactate

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24
Q

Mannitol Salt is a ___ medium.

A

selective

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25
Q

Which medium is used for isolation or detection of Staphylococcus?

A

Mannitol-salt

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26
Q

What inhibits most gram negative and many gram positive in the selective media (Mannitol-salt)?

A

High NaCl concentration.

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27
Q

Example of a mannitol fermenter (mannitol +)

What color is it?

A
  • Staphylococcus aurea.

- Yellow

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28
Q

+ mannitol fermenters : __

- mannitol fermenters : __

A
  • yellow

- pink

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29
Q

Example of negative mannitol fermenter.

A

Staphylococcus epidermidis

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30
Q

Why count bacteria growth?

A
  • to evaluate contamination of food, water
  • to ensure enough microorganisms are inoculated (ex; beer, wine, yogurt, cheese)
  • to evaluate the efficiency of antimicrobial agents
  • to study microbial populations from different ecosystems.
  • to measure effect of mutation of gens involved in metabolic pathway, survival, protection, virulence, etc
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31
Q

Results are reliable when how many colonies?

A

Between 30 - 300

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32
Q

What type of growth medium is required to enumerate bacteria?

A

A permissive growth medium.

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33
Q

What are 2 methods to enumerate bacteria?

A
  • the spread-plate method

- the pour plate method

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34
Q

Steps of spread-plate method.

A
  • sample is pipetted onto surface of agar plate
  • sample is spread evenly over surface of agar using a sterile glass spreader
  • incubation time
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35
Q

Steps of pour-plate method.

A
  • sample is pipetted into sterile plate
  • sterile medium is added and mixed well with inoculum
  • solidification and incubation
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36
Q

What can be made to get a viable count of bacterial cultures that can reach billions of cells.

A

A serial dilution.

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37
Q

What can affect the results of a serial dilution?

A

The skills of the technician.

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38
Q

What is the CFU formula?

A

CFU= (number of colonies)/ (dilution plated x volume plated)

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39
Q

What can be used to differentiate dead and live cells in the lab?

A

Viability staining.

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40
Q

During microscopic counts what is counted? (3)

A
  • dead cells
  • alive cells
  • cells that can’t be grown in lab
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41
Q

In viability staining, dead cells are ___ and live cells are ___.

A
  • dead : red

- alive : green

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42
Q

What are the pros of viability staining?

A
  • fast

- no need to wait until bacteria has grown

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43
Q

What are the cons of viability staining?

A
  • small cells can be missed

- motile cells are hard to count and must be immobilised

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44
Q

Microscopic counts are done on what?

What does it consist of?

A
  • A counting chamber.

- consists of a whole grid with 25 large squares. 1 large square has 16 small squares..

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45
Q

What is used to count during viability staining (large/small squares)?

A

several large squares are counted and the number is averaged.

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46
Q

Formula used when doing microscopic counts.

A

number of cells in a large square x 25 large squares x 50 x 10^3

47
Q

What is better at counting big cells such as protozoan, yeast, mammalian cells?

A

Flow cytometry.

48
Q

What can flow cytometry be used for?

A
  • to sort cells according to size, shape, labelling
49
Q

What occurs in flow cytometry.

A
  1. Sample enters the nozzle. sample = stained cells in suspension
  2. Hydrodynamic Focusing.
    Cells pass through in ‘single file’
  3. Laser light source.
    Allows the detection of fluorescent dyes. When stained cells : fluorescence emitted.
50
Q

What does the detection of fluorescent dyes allow?

A

Allows labelling of specific cell types or species.

51
Q

For flow cytometry where are black dots are seen during :

  • dead control
  • live control
  • test
A
  • dead control : dead cells are signalled with many black dots
  • live control : live cells have black dots
  • test : dots are equivalent for Iive and dead cells
52
Q

What does the turbidimetric method measure?

A

It measures the contribution of both living and dead cells to turbidity.

53
Q

In the turbidimetric method what is affected by properties of cells (clumping, size…)

A

OD (optical density)

54
Q

Optical density is high when water is the most or least turbid?

A

Most turbid.

55
Q

What needs to be established? (2)

A
  • A standard curve must be made

- relationship between OD and cell number

56
Q

Time needed for the population to double =

A

Generation time

57
Q

What does the generation time depend on? (2)

A
  • the growth medium

- the conditions

58
Q

When conditions are right, microorganisms grow ___ .

The population ___ at a ___ rate.

A
  • exponentially
  • doubles
  • constant
59
Q

Formula to calculate the number of cells (N).

A

N= (number of cells initially) x (2^number of generation)

60
Q

Difference between a logarithmic and arithmetic curve.

A

logarithmic : straight curve

arithmetic : exponential

61
Q

How to calculate the generation time (g)?

A

g= t/n
t-time
n-number of generation
g-generation time

62
Q

What is the form of a generation curve?

A

Straight line, increases.

63
Q

What are the 4 growth phases in a batch culture?

A
  • Lag
  • Exponential
  • Stationary
  • Death
64
Q

Which has a more viable organisms in the stationary phase (viable count or turbidity count)?

A

Viable count

65
Q

Time needed by the bacteria to adjust to new condition is the __ phase.

A

Lag

66
Q

The growth in the lag phase is __.

A

Slow

67
Q

Doubling of the population at a constant rate is in the ___ phase.

A

Exponential.

68
Q

What occurs in the stationary phase? (4)

A
  • limiting nutrients are depleted or accumulation of product inhibits growth
  • growth is stopped
  • no net increase in cell number
  • induction of “survival” systems.
69
Q

Are cells still metabolically active in the stationary phase?

A

Yes

70
Q

Cells start to die, metabolism has stopped and some cases cell death occurs with cell lysis in the __ phase.

A

Death.

71
Q

What type of function is the death phase?

A

Exponential.

72
Q

What type of culture is continually being affected by the metabolic activities of the growing microorganism (depletion of nutrients, generation of toxic waste)?

A

Batch cultures.

73
Q

Most natural environments are __ systems.

A

Open

74
Q

What do open systems experience? (4)

A
  • constant supply of nutrients and diffusion of waste
  • competition with other microorganism
  • predation (protozoan, worms)
  • changing environmental conditions
75
Q

What to most environment systems reach over time?

A

An equilibrium

76
Q

What is an equilibrium?

A

A division rate= death rate

77
Q

What is the main factor of a limiting growth factor?

A

the concentration

78
Q

What can be used in the lab to keep microorganisms in a CONSTANT growth rate over a long period of time?

A

Chemostats

79
Q

Describe a chemostat.

A
  1. Fresh medium (supply of limiting nutrients) from reservoir passes through flow-rate regulator.
  2. Fresh medium enters the gaseous headspace of the cultural vessel.
  3. The overflow of medium escapes, it contains dead microbial cells.
80
Q

What happens when equilibrium is reached? (2)

A
  • The number of cells is constant

- the growth rate = death rate

81
Q

Fact about concentration of a limiting nutrient

A
  • fresh medium

- aeration

82
Q

Facts about dilution rate

A
  • addition of fresh medium

- washout

83
Q

What affects growth in nature? (7)

A
  • nutrients
  • temperature
  • pH
  • osmolarity
  • oxygen
  • pressure
  • radiation (visible light, UV light)
84
Q

Microorganisms that grow preferentially under extreme conditions are __

A

Extremophiles

85
Q

__ % of microbial species have never been grown as a pure culture in the laboratory.

A

99

86
Q

What does minimum temperature cause?

A
  • membrane gelling

- growth can’t occur because transport processes are slow

87
Q

What does maximum temperature cause?

A
  • protein denaturation
  • collapse of the cytoplasmic membrane
  • thermal lysis
88
Q

What does optimum temperature cause?

A
  • enzymatic reactions occur at maximum possible rate
89
Q

Organisms that can grow at 0°C but have optima around 20 to 40 °C are called __

A

psychrotolerant

90
Q

Organisms that have optima at :

  • 4°C are ___
  • 39°C are ___
  • 60°C are ___
  • 88°C & 106°C are ___
A
  • psychrophile
  • mesophile
  • thermophile
  • hyperthermophile
91
Q

Escherichia coli is __

A

Mesophile

92
Q

What kills micro-organisms?

A

Ice crystals (cold temperature doesn’t kill them)

93
Q

Microbial cultures are preserves at -80°C or -196°C in __.

A

Liquid nitrogen

94
Q

How do microbes adapt to cold temperatures?

A
  • change in protein structure and sequence so enzyme can be active
  • transport across the membrane is optimal
  • cytoplasmic membrane is modifies to stay fluid
  • cold-shock proteins help keep proteins active.
95
Q

What are antifreeze proteins (glycerol) that help the formation of ice crystals that can puncture the cytoplasmic membrane?

A

Cryoprotectants

96
Q

What grows best at high pressure?

A

Barophilic (piezophilic)

97
Q

characteristics of a hydrothermal vent (2)

A
  • high temp

- high pressure

98
Q

What can heat-stable enzymes be useful for?

Example

A
  • biotechnology

- tas polymerase

99
Q

What helps resist high temperatures but aren’t metabolically active?

A

Endospores

100
Q

How does microbial life adapt at high temperature?

A
  • change in protein sequence so enzymes aren’t denatured
  • transport across the membrane functions optimally
  • modification of cytoplasmic membrane so it remains stable
  • heat shock proteins keep proteins in active conformation
  • DNA stabilise by projection mechanisms
101
Q

Enzymes at high temperature are ___

A

heat-stable

102
Q

What are :

  • alkaliphiles
  • acidophiles
  • neutrophiles
A
  • pH >= 8
  • ph <= 5.5
  • ph > 5.5 and <8
103
Q

What happens at low pH?

A

Low pH : cytoplasmic modification require high concentration of protons.

104
Q

What happens at high pH

A

High pH : cytoplasmic modification because low composition of protons, sodium-dependent pumps used for transport and motility

105
Q

Microorganisms that can grow at high salt concentrations are called ___
What do they usually require for growth?

A
  • halophiles

- NaCl

106
Q

Example of nonhalophiles

A

E. coli

107
Q

Difference between obligate and facultative aerobes?

A

Obligate - require O2

Facultative - don’t require O2 but grows better with it

108
Q

What indication is used to differentiate toxic and anoxic zones?

A

Redox indicator reazurin

109
Q

Composition of tubes for

  • obligate aerobes
  • anaerobes
  • facultative aerobes
  • microaerophiles
  • aerotolerant anaerobes
A

oxic zone - anoxic zone

  1. a lot of microorganisms - none
  2. no microorganisms - microorganisms mainly at bottom of tube
  3. most microorganisms -microorganisms homogeneously present
  4. few microorganisms in both phases
  5. many microorganisms homogeneously in both phases
110
Q

During oxygenic photosynthesis, __ is oxidised to __

A

H2O -> O2

111
Q

During aerobic respiration and oxygenic photosynthesis, what is produced?

A

toxic forms of oxygen

112
Q

Aerobes and facultative aerobes usually have __ and __

A

catalase; superoxide dismutase

113
Q

If anaerobes have the same enzymes a aerobes they are __.

A

aerotolerant anaerobes (they can grow in presence of oxygen).

Microbiology (6 decks)

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