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Microbio Midterm II > Lecture 8: Microbial Growth > Flashcards

Lecture 8: Microbial Growth Flashcards

1
Q

What is growth?

A

Increase in # of cells or biomass

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2
Q

Which nutrient sources undergo many transformations before incorporation?

A

Sources of carbon and energy

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3
Q

Which of these is not a macronutrient?

a. Mg
b. S
c. N
d. Fe
e. Ca

A

d

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4
Q

In what form are sources of Mg usually found?

A

In solution or in salts

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5
Q

What are growth factors?

A

Cannot be made by the organism, needed for growth. Ie. Vitamins, AAs, Purines, Pyrimidines

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6
Q

True or False: growth factors can be the byproduct or waste of another microorganism.

A

True

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7
Q

How do prokaryotes reproduce?

A

Via binary fission

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8
Q

What are the 3 steps of binary fission?

A
  1. Cell Elongation
  2. Septum Formation
  3. Completion of septum, formation of cell walls, and separation
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9
Q

What constitutes as 1 generation of reproduction?

A

When 1 cell divides into 2=1 generation

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10
Q

What enzyme cleaves the cell wall in binary fission?

A

Autolysins

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11
Q

Why is the cell wall cleaved in binary fission? (Not for separation)

A

Autolysins break down the cell wall in small sections so growth can occur (peptidylglycan is very rigid)

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12
Q

What is bactoprenol used for in binary fission?

A

Allows peptidylglycan subunits to be exported across cytoplasmic membrane (makes them hydrophobic) & inserts them at point of growth in cell wall.

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13
Q

What is transglycosylase used for in binary fission?

A

Adds peptidyglycan monomers to the cell wall. Catalyze glycosidic bond formation (transpeptidation)

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14
Q

What is bactoprenol?

A

Lipid carrier molecule, bind to NAG/NAM of peptidylglycan monomers

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15
Q

What bonds to autolysins cleave?

A

Hydrolyze bonds that connect NAG to NAM @ FtsZ ring (Allows synth of new cell wall and peptide rearrangement)

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16
Q

What kind of medium is MacConkey Agar?

A

Selective, Differential

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17
Q

What is in MacConkey Agar?

A

Bile salts, crystal violet, red dye

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18
Q

What colour do lactose fermenters produce on MacConkey Agar?

A

Pink (colourless is non-lactose fermenter)

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19
Q

True or False: E. coli is a lactose fermenter.

A

True

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20
Q

What kind of growth does MacConkey agar inhibit?

A

Gram negative (its the bile salts and crystal violet that inhibit it)

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21
Q

What kind of medium is Mannitol-Salt Agar?

A

Selective and differential

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22
Q

Whats in Mannitol-Salt agar?

A

High NaCl concentration

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23
Q

What kind of growth does Mannitol-Salt agar inhibit?

A

inhibits most gram - bact. as well as some gram +

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24
Q

What is an indicator that the organism on a Mannitol-Salt agar ferments mannitol?

A

Mannitol fermenters turn the agar yellow (pink if non-mannitol fermenter)

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25
Q

What is Mannitol-Salt agar commonly used to isolate?

A

S. aureus (Mannitol fermenter)

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26
Q

What is a viable cell?

A

Cell able to divide and form offspring

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27
Q

What does CFU stand for?

A

Colony forming unit

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28
Q

What is a wall band?

A

Scar formed in binary fission between new and old cell wall.

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29
Q

What is the spread plate method of counting bacteria?

A

0.1ml or less pipetted onto solid agar, then sample is spread and incubated

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30
Q

What is the pour plate method of counting bacteria?

A

Sample pipetted onto sterile plate, medium added and incubated.

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31
Q

How do you perform a serial dilution?

A

(10^-1) remove 1ml of sample and dilute into 9ml of broth

(10^-2) remove 1ml of diluted solution and add to 9 more ml of broth

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32
Q

What is the equation for CFU?

A

(# of colonies)/(dilution plated)(volume plated)

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33
Q

What is the formula for generation time?

A

N=No2^n
(N=final# of cells, n=# of generations)
and

g=t/n (g=generation time)

34
Q

Is a batch culture a open or closed system?

A

Closed= constantly affected by metabolic activity of growing microorganism

35
Q

What is a continuous culture?

A

Open system=constant input of nutrients and removal of waste. Reaches equilibrium.

36
Q

What is flow cytometry?

A

Cells are stained, then driven in a narrow tube single file. A laser is shined at the tube. If cells scatter laser, they are counted. Cells can be tagged to emit fluorescence when going through the laser.

37
Q

What kind of cells are best to use with flow cytometry?

A

Big cells, and it can be used to detect fluorescent labelled cells and sort cells.

38
Q

What is the tubidimetric method of counting cells?

A

Cell suspensions look cloudy (turbid) because cells scatter light-more cells=more light scattered. Therefore, more turbid=more cells.

39
Q

How is the tubidimetric method used to count cells?

A
  1. Light is shone through prism and filter, at the sample.

2. Spectrophotometer measures unscattered light.

40
Q

True or False: Low temperatures kill microorganisms.

A

False, the low temperature doesn’t kill them the ice crystals do.

41
Q

What are the ways a microbe adapts to life in the cold?

a. changes in protein structure so enzymes active at low temp
b. membrane transport optimal at low temp
c. membrane modified to stay fluid
d. cold shock proteins (cryoprotectants-prevent ice crystal formation)
e. all of the above

A

e

42
Q

What is the lag phase?

A

Slow growth, bacteria is adjusting to new environment.

43
Q

What is the exponential phase?

A

Doubling population at a constant rate.

44
Q

What is the stationary phase?

A

No net increase in cell #. Limiting nutrients have been depleted or waste is accumulating. Growth has stopped but cells are still metabolically active.

45
Q

What is the death phase?

A

Cells start to die exponentially.

46
Q

What is a chemostat?

A

Used in the lab to keep organisms in constant growth over a period of time. Supplies fresh medium and removes dead organisms.

47
Q

What happens when you reduce the dilution rate?

A

Decrease growth rate

48
Q

What happens when you increase the dilution rate?

A

Increase growth rate

49
Q

What are cardinal temperatures?

A

Min and max temperatures that define limits of growth of an organism.

50
Q

What happens when the temperature is too low for an organism?

A

Membrane gells, transport is so slow that growth is inhibited.

51
Q

What happens when the temperature is too hot for an organism?

A

Proteins are denatured, cytoplasmic membrane collapses due to thermal lysis.

52
Q

What are the techniques you can use to measure total cell count?

A

Microscopic counts, flow cytometry

53
Q

What are the techniques you can use to measure viable cell count?

A

Viable (plate counts), staining + microscopic count/flow cytometry

54
Q

What does psychrotolerant mean?

A

Can grow at 0C, optimum at 20-40 celsius

55
Q

What are the cardinal temperatures of a psychrophile?

A

-5-12C (Optimal at 4)

56
Q

What are the cardinal temperatures of a mesophile?

A

9-47C (Optimal at 39)

57
Q

What are the cardinal temperatures of a thermophile?

A

41-69C (Optimal at 60)

58
Q

What are the cardinal temperatures of a hyperthermophile?

A

65-95C (Optimal at 88)

59
Q

What kind of bacteria grow best at high pressure?

A

Barophillic/piezophillic bacteria

60
Q

What are the ways a microbe adapts to life in high temperatures?

A
  • Changes protein sequence so enzymes not denatured
  • Transport across membrane optimal at high temperatures
  • Membrane modified to be stable at high temperatures
  • Heat shock proteins=keep proteins in active conformation
  • DNA is GC rich (3 H bonds)
61
Q

What is a neutrophile?

A

5.5

62
Q

What is a acidophile?

A

pH<5.5

63
Q

What is a alkaliphile?

A

pH>8

64
Q

How do microbes adapt to life in a low pH?

A

Changes membrane to need a high [H+] to be stable-bacteria lyse at higher pH because membrane becomes unstable

65
Q

How do microbes adapt to life in a high pH?

A
  • Changes membrane to withstand a low [H+].
  • Uses Na+ gradient for transport and motility (low [H+]=pmf is hard to maintain).
  • Keeps ETC close to ATPase so H+ pumped out doesn’t diffuse.
66
Q

What is a halophile?

A

Bacteria that can frow at high [NaCl]. Up to 12%

67
Q

What % NaCl can a halotolerant microbe endure?

A

0-11%

68
Q

What % NaCl can halophillic microbes endure?

A

Often require seawater to grow (3%)

69
Q

What % NaCl can extreme halophiles endure?

A

11-25%

70
Q

What is an obligate aerobe?

A

O2 required

71
Q

What is a facultative aerobe?

A

O2 not required. Anaerobic or aerobic respiration possible.

72
Q

What is a microaerophillic aerobe?

A

O2 required but at lower levels than than atmospheric.

73
Q

What is an aerotolerant anaerobe?

A

Growth no better with O2, uses fermentation

74
Q

What is an obligate anaerobe?

A

O2 harmful

75
Q

How do you test if an organism is an aerobe or anaerobe?

A
  1. add Thioglycolate-reduces O2 to H2O (creates O2 gradient in tube)
  2. Redox indicator reazurin used to differentiate zones (Pink when oxidized)
76
Q

When are toxic forms of O2 produced?

A
  • During aerobic respiration (O2 oxidized to H2O)
  • During oxygenic photosynthesis (H2O oxidized to O2)
  • Flavoproteins quinone and FeS proteins can also reduce O2->O2-
77
Q

What is a superoxide?

A

O2-

78
Q

What is a hydroxyl radical?

A

OH.

79
Q

Why are aerobes and facultative aerobes resistant to toxic O2? (also some aerotolerant anaerobes)

A

Have catalase/superoxide dismutase/peroxidase

80
Q

What does catalase do?

A

Converts H2O2 to H2O and O2

81
Q

What does superoxide dismutase do?

A

Converts O2- to H2O2 and O2

Microbio Midterm II (7 decks)

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