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Microbiology > Lecture 8: Bacterial Growth in the Lab > Flashcards

Lecture 8: Bacterial Growth in the Lab Flashcards

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Biology 101 flashcards
1
Q

Where can bacteria grow in a lab?

A
  • agar plates
  • broth
  • nutrient rich media
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2
Q

Growth in nutrient rich media takes on
the form of ________ growth

A

logarithmic growth

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3
Q

Logarithmic growth

A
  • Binary fission - 1, 2, 4, 8, 16…
     Growth rate can be expressed as doubling
    time
     E. coli has a doubling time in rich broth culture of 20 min
     More formally, N=N0e^kt
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4
Q

How to measure microbial growth?

A
  • perform measurements on liquid cultures only
  • plate counts
  • optical density (turbidity)
  • Microscopic visualization
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5
Q

Plate counts

A

count number of colony forming units (CFU) on plate

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6
Q

Optical density (turbidity)

A

direct measure the ability to absorb light at a specific wavelength

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7
Q

microscopic visualization

A

count bacteria in a given amount of culture directly

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8
Q

how to conduct plate counts?

A

 Dilute culture in an appropriate buffer/
medium (serial dilutions)
 If sample is very dilute, may use filtration method to concentrate instead
 Plate onto nutrient agar plates
 Count colonies (CFUs) after right amount of time (24h for standard
organisms)

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9
Q

Advantages and disadvantages of plate counts

A

advantage- only counts bacteria capable of dividing (CFU)
 Disadvantage- takes time to do; subject to experimenter error in dilution

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10
Q

How to do optical density (turbidity)

A

 Use a spectrophotometer
 Shines light at a specific
wavelength through the culture, measures the amount that passes
through (transmittance or its converse, absorbance)

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11
Q

Advantages and disadvantages of turbidity

A
  • Advantage- quick, accurate
    method for determining density of
    culture
     Disadvantage- may count dead cells
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12
Q

How to do microscopy?

A

 Take direct sample, count cells (use
hemocytometer or Petroff-Hauser cell counter)

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13
Q

Advantage and disadvantage of microscopy

A

 Advantage-quick, precise
 Disadvantage- may vary greatly from field to field, so need to observe many fields to get statistically relevant numbers
 Disadvantage- doesn’t distinguish live from dead cells
 Disadvantage- intensive compared to other two techniques
 This is not commonly used for cell counting

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14
Q

Logarithmic growth phases

A

bacterial culture growth has 4 phases
- lag
- log phase
- stationary phase
- death phase

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15
Q

Lag phase

A

when inoculating
a culture, cells take
time to adjust to new
environs

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16
Q

Log phase

A

maximal growth rate
 N=N0e^kt
 Calculate doubling time
(N=2N0)

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17
Q

Stationary phase

A

number of cells is
steady

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18
Q

Death phase

A

rate of cell death exceeds division rate

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19
Q

Solve N=Noe^kt
No=100, N =3200, t=300

A

3200 = 100e^k(300)
32 = e^300k
ln32 = 300k
ln32/300 = k
k = doubled

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20
Q

tD is when N = 2No

A

2No = Noe^ktD
2 = e^ktD
ln2 = ktD
tD = ln2/k

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21
Q

Solve N=Noe^kt
No=300, N =600, t= 60

then plug into tD equation

A

600= 300e^k(300-240)
2= e^k(60)
ln2 = 60k
ln2/60 = k

tD = ln2/(ln2/60)
tD = 60

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22
Q

What kind of culture does logarithmic growth curve describe?

A

batch cultures

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23
Q

What is batch culture?

A

The microbes are exposed to the same media, even as they utilize the nutrients and release various products

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24
Q

Where is continuous culture done?

A

in a chemostat

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25
Q

What is continuous culture?

A

The spent media (containing bacteria) is removed, and fresh
media added, at a constant flow rate

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26
Q

Chemostat culture graph

A

D = f/V
- at low dilution rates, growth rate proportional to D (Monod)
maintenance energy
high dilution rates - washout

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27
Q

What environmental factors affect growth rate?

A
  • temperature
  • pH
  • water activity
  • oxygen
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28
Q

psychrophilic

A

cold loving

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29
Q

thermophile

A

heat loving

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30
Q

mesophile

A

moderate temp. loving

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31
Q

hyperthermophile

A

high temp. loving

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32
Q

Why does temperature curves have that asymmetrical shape?

A

after you reach optimal temp. the cells immediately inhibit growth and eventually denature at the higher temperatures.

33
Q

What do cardinal temperatures reflect?

A

reflect niche where normally found

34
Q

What bacterium are found in skin (can tell by their cardinal temperatures 30-37)?

A
  • listeria monocytogenes
  • staphylococcus aureus
35
Q

acidophile

A

acidic condition loving

36
Q

neutrophile

A

neutral pH loving

37
Q

alkalophile

A

high pH loving

38
Q

How does chemiosmosis work?

A

uses proton gradient to generate ATP across a membrane

39
Q

compatible solutes

A

a molecule that doesn’t interfere with the biochemistry happening in a cell, but pulls water into the cell ( or holds water in the cell)
- modulate osmolyte concentration so it can quickly change whether to release or retain water.

40
Q

how does bacteria make compatible solutes?

A
  • manipulate ion flows across a membrane
  • make derivative compounds of simple ones they use a lot, to use them as a compatible solute temporarily (ex: trehalose)
41
Q

osmotic pressure

A

solutes
- salts

42
Q

halophile

A

salty conditions

43
Q

matric pressure

A

absorption to solids
- desiccation

44
Q

water activity

A

available water for organisms
- proportion of water available for biochemistry

45
Q

low water activity

A

makes life difficult

46
Q

formula for water activity

A

aw = Psoln / Pwater

47
Q

desiccation

A

loss of water? no water?

48
Q

What protects against modest changes in water activity?

A

the cell wall

49
Q

What happens at low water activity?

A

DNA disordering

50
Q

What is botulism? What food is a known botulism carrier? Who is at risk of it?

A

Clostridium botulinum
- a rare illness caused by a toxin that attacks the body’s nerves and causes difficulty breathing, muscle paralysis, and even death
- honey
- babies, not adults because we already have bacteria in our gut so clostridium botulinum cant plant itself in our gut.

51
Q

staphylococci

A

facultative anaerobes?
(use oxygen when its there, doesn’t use it when its not)

52
Q

streptococci

A

aerotolerant anaerobe
(ignore oxygen completely)
- never aerobes
- always anaerobes

53
Q

Other factors on microbial growth

A
  • radiation
  • pressure
54
Q

Radiation

A

 UV, ionizing
 DNA damage T-T
dimers
 Deinococcus
radiodurans
 Endospores

55
Q

barophilic

A

high pressure

56
Q

barotolerant

A

can survive high or normal pressures

57
Q

piezophilic

A
  • deep sea
    lives under elevated hydrostatic pressure
58
Q

Liebig’s law of the minimum

A

total biomass of organism determined by nutrient present at lowest concentration

59
Q

Shelford’s law of tolerance

A

above or below certain environmental limits, a microorganism will not grow, regardless of the nutrient supply

60
Q

Nutrient stress (oligotrophy) May result in ___________ in cells

A

physiological changes

61
Q

Viable but non-culturable (VBNC)

A

 Can be identified by staining protocols
 Postgate microviability
 Morphological changes at single cell level
 Many bacteria studied show capacity

62
Q

All organisms need ____ and energy to survive

A

carbon

63
Q

Carbon sources

A
  • autotrophy
  • heterotrophy
64
Q

autotrophy

A

fixation of carbon dioxide (gets it from the environment?)

65
Q

heterotrophy

A

use of organic carbon

66
Q

energy sources

A
  • prototrophy
  • chemotrophy
67
Q

phototrophy

A

energy from light

68
Q

chemotrophy

A

energy from chemical reactions

69
Q

photoautotroph

A

light and fix CO2

70
Q

photoheterotroph

A

light and uses organic carbon

71
Q

chemoautotroph

A

chemical rx and fix CO2

72
Q

chemoheterotroph

A

chem rxs and uses organic carbon

73
Q

Redox reactions generate…

A

cell energy

74
Q

Where is the energy cells need stored?

A

in chemical bonds

75
Q

what forms bonds in a molecule?

A

electrons

76
Q

______ are moved between molecules by ____ reactions

A
  • electrons
  • redox
77
Q

In biological systems, oxidation of the nutrient is coupled with….

A

reduction of an electron carrier

78
Q

What does a carrier do to electrons?

A

can transfer electrons from the nutrient molecule to other systems, where it is converted to ATP

79
Q

OILRIG

A
  • oxidation is loss
  • reduction is gain

Microbiology (16 decks)

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