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Microbiology > Microbial growth > Flashcards

Microbial growth Flashcards

1
Q

What are growth factors?

A

Organic molecules that the microorganisms need for growth but cannot synthesize by itself. Some growth factors are the by-product or waste of another microorganism.

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2
Q

Exemple of growth factors?

A

Vitamins, a.a. , purines, pyrimidines or other…

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3
Q

What are siderophores?

A

Shuttles to get iron. Molecule that will bidn to iron

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4
Q

What form or Iron can be taken up by cells? In what condition?

A

Ferrous ( 2+) or soluble form , in anoxic condition

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5
Q

What form of Iron cannot be taken up by cells? In what condition?

A

Ferric (3+) or insoluble. In oxic conditions.

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6
Q

What particular nutrient is limiting nutrient in nature and really important for many enzymes in resp. and photosynth?

A

IRON

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7
Q

What is growth of a population?

A

Increase in number of cells or in biomass

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8
Q

Most prokaryotes multiply by…

A

Binary fission

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9
Q

Steps of binary fission?

A
  • CEll elongation
  • Spetum formation
  • Completion of septum, formation of walls, cell separation
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10
Q

What enzyme is involved in division of bacteria with peptidoglycan?

A

Autolysin and Bactoprenol

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11
Q

What is the role of Autolysin?

A

Destruction of peptidoglycan

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12
Q

What is the role of Bactoprenol?

A

Allows peptidoglycan subunits to be exported across the cytoplasmic membrane

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13
Q

What will decide where there has to be a fission/ making new peptidoglycan in division of bacteria?

A

FtsZ ring, or division ring

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14
Q

What is a wall band?

A

Scar between old and new peptidoglycan

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15
Q

Why is macconkey plate selective?

A

Because bile salts inhibits growth of Gram +

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16
Q

Why is MacConkey differential?

A

Because it contains lactose, and a pH indicator: only bacteria fermenting lactose will produce acid–> indicator = pink color on the plate

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17
Q

What does E.Coli form on a macconkey plate?

A

Dark pink colonies with bile precipitate: “ I don’t care about bile, I will destroy it”

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18
Q

Why is Manitol-salt selective?

A

Hight in NaCl concentration–> inhibits growth of most Gram -, and many Gram +

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19
Q

Why is mannitol-salt plates differential?

A

Mannitol fermenters will turn yellow

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20
Q

Exemple of a mannitol fermenter?

A

Straphylococcus aureus

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21
Q

Name all methods to measure microbial growth/presence.

A
  • Viable Count
  • Serial dilution
  • Microscopic counts
  • Flow cytometry
  • Turbidimetric method
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22
Q

Describe viable count method

A
  • Spread-plate method
  • Pour plate method
  • Need a permissive growth medium
  • Results are reliable when there are between 30-300 colonies
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23
Q

How can you get a viable count with serial dilution?

A

CFU calculation: number of colonies/ dilution plated x volume plated

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24
Q

Microscopic count ?

A
  • Use of a petroff-hauser chamber
  • Count all cells, dead or alive…
  • Can use viability staining to differenciate dead or alive
  • Small cells can be missed.. motily, immobilize
25
Q

Flow cytometry?

A
  • Better at counting big cells : protozoans, yeast, mammalian cells etc.
  • need of a DYE!
  • Detection of dye allow labelling of sepcific cell types pr species
  • Can be used to sort cells according to size/shape
26
Q

turbidity method ?

A
  • Measure alive or dead cells
  • Can be affected by clumping or attachment to surface of cells
  • Optical density is affacted by size, shape composition cell inclusion etc.
  • Curve compare relationship between OD and cell number
27
Q

What is generation time?

A
  • Time needed for the population to double
28
Q

On what do generation time depend?

A
  • Growth medium

- Conditions

29
Q

How to calculate the number of cells?

A

N= N0*2^n

N= number of cells
N0= Number of cells initially
n= number of generation (number of time doubled)
30
Q

How to calculate generation time?

A

g=t/n

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

31
Q

What are the steps of a growth cycle in a batch culture (in a tube)?

A
  • Lag phase: Time needed to ADJUST to new condition, SLOW growth
  • Exponential phase: DOUBLING of the population at a constant rate
  • Stationary phase: limiting nutrients are depleted or accumulation of a waste product that inhibits growth. GROWTH IS STOPPED. SURVIVAL PHASE.
  • Death phase: Cells start to die, metabolism has stopped. EXPONENTIAL.
32
Q

Particularity of batch culture?

A

CLOSED SYSTEM

-Affected by the metabolic activities of the growing microorganism: depletion of nutrients, generation of toxic waste.

33
Q

What is a continuous culture?

A
  • OPEN SYSTEM
  • Reaches EQUILIBRIUM:
    division rate= death rate
  • constant supply of nutrients
  • constant diffusion of waste
34
Q

What are factors affecting growth of organisms?

A
  • Nutrients
  • Temperature
  • PH
  • Radiation
  • Oxygen
  • Osmolarity
  • Pressure
35
Q

What do we call organisms that grow preferentially under extreme conditions?

A

Extremophiles

36
Q

What are the 3 points on the curve of temperature affecting growth?

A
  • Minimum: membrane gelling, transport processes are slowed down, so that growth is not possible
  • Optimum: enzymatic reaction occuring at maximal rate
  • Maximum: denaturation of enzymes , collapse of the cytoplasmic membrane, thermal lysis
37
Q

How do we call organisms growing from -X-10 degres?

A

phsychrophiles

38
Q

How do we call organisms growing best at 39?

A

Mesophiles

39
Q

How do we call organisms growing best at 60 degres?

A

Thermophiles

40
Q

How do we call organisms growing best at higher than 60 degres?

A

Hyperthermophiles

41
Q

What are adaptations made by organisms that live in COLD environment?

A
  • Changes in PROTS STRUCTURE
  • Modification of the CYTOPLASMIC MEMBRANE so its stays more FLUID.
  • COLD-SHOCK PROTEINS which help keep proteins stay active
  • CRYOPROTECTANTS (antifreeze proteins ), glycerols help prevent the formation of ICE CRYSTALS that could puncture the cytoplasmic membrane
42
Q

Does cold kill microorganisms?

A

No! ice crystals do!

43
Q

How are microbial cultures preserved?

A

at -80 to -196 in liquid nitrogen

44
Q

How do we call organisms that grow best at high pressure?

A

Barophilic organisms

45
Q

What are adaptations made by organisms that live in HOT environment?

A
  • Change in protein sequences so that enzymes are not denatured
  • Modification of cytoplasmic membrane so it remains more RIGID (ex: lipid monolayer of archeas)
  • HEAT-SHOCK proteins which help keep prots in active formation
  • Protection mechanisms to ensure stability of DNA (GC rich –> 3 links)
46
Q

Does hot temperatures kill microorganisms

A

yes! –> THERMAL LYSIS

47
Q

What are adaptations made by organisms that live in LOW PH environment?

A
  • changes in cytoplasmic membrane to resist HIGH CONCENTRATION PROTONS.
  • usually, membrane requires high concentration of protons for stability. Bacteria lyse at high pH because membrane is unstable
48
Q

What are adaptations made by organisms that live in HIGH PH environment?

A
  • changes in cytoplasmic membrane to resist low concentration protons
  • Use of Na+ gradient for transport motility
  • ## Keep the electron transport chain close to th ATPase, so p+ that are pumped out do not diffuse away
49
Q

What is internal pH?

A
  • DNA= acid-labile
  • RNA = alkali-labile
  • Internal pH limits= 4.6- 9.5 (with protection systems not fully understood yet)
50
Q

What is used to keep the pH steady in a growth medium and why?

A

Buffer, because waste can often affect pH (ex: MacConkey)

51
Q

What do we call microorganisms that can grow in high salt concentration?

A

Halophiles

52
Q

What is the % of salt in sea water?

53
Q

What are the groups of aerobes? and what is their metabolism?

A
  • Obligate (oxygen required): aerobic respiration
  • Facultative (not required, but growth is better): aerobic or anaerobic respiration
  • Microaerophilic ( require oxygen but at low level) : aerobic respiration
54
Q

What are the groups of anaerobes?

A
  • Aerotolerant (do not require oxygen , and growth is not affected) : fermentation
  • Obligate (oxygen is harmful/lethal) : fermentation or anaerobic respiration
55
Q

What adjustment to the medium needs to be made for obligate and facultative aerobes to grow?

A
  • Liquid medium

- Needs to be shaken constantly, so sufficient amount of oxygen present in medium.

56
Q

What is added to a liquid medium to know the oxic zone, and how does in work?

A

Thyoglycolate. Reduces O2 to H2O. , creating a gradient of oxygen concentration.

57
Q

What is the danger with toxic forms of oxygen?

A

They oxidize cell components, stopping key metabolic pathways and destroying key structures.

58
Q

What compound can reduce O2 to O2-?

A

Flavoproteins, quinone, iron sulfur proteins

59
Q

What enzymes are used to take care of toxic forms of oxygen , and in what types of aerobes?

A

Catalase and superoxide dismutase. They are present in aerobes and facultative aerobes.

Microbiology (11 decks)

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