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LSCI230 > W4-lecture 2: Microbial growth > Flashcards

W4-lecture 2: Microbial growth Flashcards

1
Q

What is the name of the enzyme that will destruct the peptidoglycan wall during cell division?

A

Autolysin

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2
Q

What is the name of the enzyme allows peptidoglycan subunit to be exported across the cytoplasmic membrane

A

Bactoprenol

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3
Q

What is the name of the ring that contains the autolysin?

A

the FtsZring

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4
Q

What are the scars that you can see near the septum on the bacteria

A

the wall bands, they separate the old and new peptidoglycan

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5
Q

What is a selective medium?

A

medium that allow the growth of only some kind of bacteria can grow on it

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6
Q

What is a differential medium?

A

medium that helps to differentiate the different kind of bacteria that grow on it

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7
Q

Give two example of selective medium ?

A

MacConkey Mannitol-salt

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8
Q

What does the macconkey medium help differentiate?

A

Differentiate (differential media) between Lactose fermenters (Pink) and Lactose non‐fermenters (colorless).

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9
Q

What does the bile salts inhbits in the macconley medium?

A

The gram+ and it is permissive for the gram enteric pathogens.

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10
Q

What does the mannitol-salt is selective for

A

Selective medium, high NaCl concentration: inhibits most Gram‐and many Gram+.

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11
Q

Name one use of the mannitol-salt medium

A

Used for isolation or detection of Staphylococcus.

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12
Q

What does the mannitol-salt help differentiate?

A

Mannitol fermenters: +, yellow; ‐, pink.

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13
Q

T or F : staphylococcus aureus is mannitol.

A

false, is is a mannitol fermenter.

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14
Q

Where will the microorganisms grow on the spread-plate technique

A

on the agar (2D)

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15
Q

Where will the microorganisms grow on the pour-plate method?

A

in 3 dimensions.

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16
Q

What is the advantage of the pour-plate method?

A

you can grow anaerobes.

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17
Q

What is used to make the count under the microscope ?

A

the counting chamber

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18
Q

If there is 159 colonies on a plate that is diluted at 10^-3, what will be the CFU?

A

CFU is the number of colonie per mL. Since there is 159 colonies in 10^-3, plate count x dilution factor is (10^3x159) so the CFU is 1.59x10^5 cells per mL of original sample

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19
Q

What are the pros and cons of the counting chamber?

A

• Pros: Fast, no need to wait until bacteria has grown (so can be done on bacteria that can’t grow). • Cons: Small cells can be missed, motile cells are hard to count and must be immobilized.

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20
Q

What counting technique would you use if you have a microorganisms that can’t grow because it is dead?

A

The microscopic count pr flow cytometry

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21
Q

what is viability staining?

A

viability staining : stains to know which cells are dead and which ones are alive

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22
Q

T or F : you can use the turbidity method to quantify only for living cells

A

false

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23
Q

what is the reason of the stationary phase in the growth phases?

A

there is some nutrients that are lacking. There will be no growth in this phase.

24
Q

name the growing phase in order

A

lag -> exponential or log-> stationary -> death

25
Q

t or F : death phase is also exponential

A

T

26
Q

What is a chemostat?

A

a continuous culture that has fresh nutrient flow in and metabolic end products flushed out at the same rate.

27
Q

What type of culture would you use if you would want to imitate what is happening in the nature

A

a continuous culture

28
Q

What is the equilibrium in microorganism?

A

division rate equals death rate.

29
Q

Under what conditions would a lag phase not occur?

A

If an exponentially growing culture is transferred into the same medium under the same conditions of growth, there will be essentially no lag and exponential growth will begin immediately.

30
Q

Why do cells enter stationary phase?

A

because of the lack of nutrients

31
Q

Explain the concept of steady state

A

in the steady state the concentration of bacteria stays the same because there is a high dilution rate so the microo are created at the same rate that they are washed out. Also they are doubling at a fast rate because they are receiving nutrients at a faster rate.

32
Q

Explain the difference between the yield and the growth rate and why at high nutrient concentration, only the yield is affected

A

has the concentration increases, the growth yield will increase (the total number of cells). When nutrient increases, the growth rate will increase but at a certain level, cell are dividing at their maximum rate and so the growth rate is stationnary while the total number of cells still increases (total yield)

33
Q

name the temperature optimum of : psychrophile, mesophile, thermophile, hyperthermophile, extra-hyperthermophile

A
34
Q

What is a psychrotolerant?

A

Organisms that can grow at 0°C but have optima around 20 to 40 °C. (listerios)

35
Q

T or F : it is the cold temperature in itself that kills the microorganisms

A

F : important point that it is not the cold that kill the bacteria but the ice crystal that puncture the bacteria

36
Q

What are barophilics?

A

Bacteira that grow best at high pressures

37
Q

What would be an adaptation of the DNA of the microbial life at high temperautre?

A

more rich in GC (3 bonds insteand of AT).

38
Q

Define the term : halotolerant, halophile, extreme halophile and nonhalophile.

A
39
Q

Define the pH for these microo. :

  • Neutrophile
  • Acidophile
  • Alkaliphile
A
  • Neutrophile : 7
  • Acidophile : <5.5
  • Alkaliphile : >5.5
40
Q

What can do the microorganisms to adapt to the low pH?

A

Changes of the cytoplasmic membrane to require high concentration of protons for membrane stability. Bacteria lyse at higher pH, because the membrane becomes unstable.

41
Q

What can do the microorganisms to adapt to the high pH?

A

– Changes of the cytoplasmic membrane to withstand low concentration of protons.

– Use of Na+ gradient for transport and motility (low concentration of protons outside, pmf is hard to maintain).

– Keep the electron transport chain close to the ATPase, so protons that are pumped out do not diffuse away.

42
Q

T or f ; the extreme halophiles can’t grow at a salt concnetration of less than 10%

A

t

43
Q

What are the factors that are affecting the microbial growth?

A
  1. oxygen
  2. Salt concentration
  3. Temperature
  4. pH
44
Q

What is a facultative aerobe?

A

microo. that can grow without O2 but is better with oxygen. It can do fermentation, anaerobic and aerobic respiration.

45
Q

what are microaerophiles

A

microaerophiles requires oxygens but at lower levels than in the atmosphere

46
Q

What are the different groups of aerobes?

A
  1. obligate
  2. facultative
  3. microaerophilic
47
Q

What are the groups of anaerobes?

A
  1. Aerotolerant
  2. obligate
48
Q

What is the difference between the aerotolerant anaerobes and obligates anaerobes

A

Aerotolerant won’t use oxygen but don’t mind the presence of oxygen while the obligate find the o2 presence lethal

49
Q

What is the name of the compound that reduces the oxygen to water to study the anaerobes microorganisms?

A

Thioglycolate

50
Q

What is the redox indicator used in the lab to indicate the anoxic and oxic zones

A

Reazurin

51
Q

indicate the group of anaerobes or aerobes

A

a) obligate aerobes
b) anaerobes
c) facultative aerobes
d) microaerophilics
e) aerotolerant anareobes

52
Q

What is the type of metabolism of the aerotolerant anaerobe?

A

fermentation

53
Q

What is the type of metabolism of the oblicate anaerobe?

A

femrentation and anaerobic respiration

54
Q

T or F : anaerobes and aerobes contain the enzymes catalase and superoxide dismutase

A

f: Anaerobes may or may not contain such enzymes. If they do, they may be aerotolerant anaerobes (can grow in presence of O2 although they do not use it). Contrasts with obligate anaerobes which are inhibited or even killed by O2.

55
Q

T or F:

A

LSCI230 (20 decks)

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