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MCR101 > Topic 5 -Microbial Growth > Flashcards

Topic 5 -Microbial Growth Flashcards

1
Q

List the requirements for microbial growth

A

Physical:
Temperature, pH, osmotic pressure

Chemical:
NCHOPS totally organic
Nitrogen, Carbon, Hydrogen, Oxygen, Phosphorous, Sulphur
Trace elements (e.g. vitamins)
Organic growth factors (e.g. Fe, Mg, Cu, Zn, Co)

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2
Q

A little bit about pH and microbes?

A 
bacteria grow b/w pH 6.5-7.5
Moulds & yeast grow b/w 5 - 6
pH controlled by buffers
Acidophiles
Alkaliphiles
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3
Q

Explain the importance of osmotic pressure to growth

A

Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.
Hypertonic enviro’s cause plasmolysis (inside of cell shrinks)

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4
Q

Use of Nitrogen (N) in growth?

A

amino acids, proteins, DNA, RNA

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5
Q

Use of Carbon (C) in growth?

A

carbohydrates, lipids, aa, DNA, RNA. Carbon for cata/anabolism.

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6
Q

Use of Hydrogen (H) in growth?

A

counter ion e.g. -OH & -COOH. Used as proton source for chemiosmotic formation of ATP

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7
Q

Use of Oxygen (O) in growth?

A

found in most organic molecules e.g. glucose.

electron acceptor

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8
Q

Use of Phosphorous/phosphate (P/Pi) in growth?

A

found as phosphate

ATP, NADP, DNA & RNA

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9
Q

Use of Sulfur (S) in growth?

A

needed for aa cysteine and methionine & co factors

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10
Q

What is the role of trace element Fe?

A

Iron.

needed for cytochromes in electron transport

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11
Q

What is the role of Trace element Mg?

A

Magnesium

Counter iron for nucleotides and ATP

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12
Q

What is the role of trace element Zn, Co, Cu & Mo?

A

Zinc, Cobalt, Copper, Molybdenum.

Enzyme cofactors

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13
Q

How do aerobes avoid damage from O2?

A 
Enzymes.
singlet oxygen=> boosts O2 to higher energy state
then to superoxide free radicals
Then to peroxide anion
then to hydroxyl radical
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14
Q

Describe the visual growth of an obilgate aerobe?

A

all near top of tube where high [] of O2.

See diagram. pg 4

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15
Q

Describe visual growth of facultative anaerobes?

A

more [] near top of tube but spread throughout tube.

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16
Q

describe visual growth of obligate anaerobes?

A

all at bottom of tube where very low to no O2

17
Q

describe visual growth of aerotolerant anaerobes?

A

spread throughout tube

18
Q

describe visual growth of microaerophiles?

A

very sensitive, need exact right conditions. Found in strip through middle of tube or to particular needs.

19
Q

Explain the purpose of organic growth factors

A

organic compounds obtained from the enviro.
e.g. vitamins, aa, purines, pyrimidines
many bacteria do not require these
some microorganisms absolutely require a particular GF

20
Q

What is a culture medium?

A

nutrients prepared for microbial growth

21
Q

what does sterile mean?

A

contains no living organisms

22
Q

what is inoculum?

A

microbes introduced into medium

23
Q

what is a culture?

A

microbes growing in/on a culture medium

24
Q

what is a pure culture?

A

contains only one species or strain

25
Q

what is a colony?

A

population of cells arising from a single cell or spore or group of attached cells

26
Q

what is a colony forming unit (CFU)?

A

number of living cells in a sample that will grow, divide & form colonies on solid media

27
Q

what is a chemically defined media for bacterial growth?

A

exact chemical composition known. Microbes make all nutrients themselves, uses a lot of energy, takes longer to grow

28
Q

what is a complex media for bacterial growth?

A

e.g. beef extract and peptone (no defined chemical composition)
Nutrients provided, faster growth

29
Q

How can single colonies be isolated?

A

streak plate method

30
Q

List the different kinds of bacterial growth (repro)

A

binary fission
budding
fragmentation of filaments
conidiospores (asexual)

31
Q

Name & describe the 4 different bacterial growth phases

A
  1. lag phase -little cell division occuring
  2. exponential (log) phase -growth phase
  3. stationary phase -bacterial death=bacterial division
  4. death phase -cell lysis occurs
32
Q

List 4 ways of measuring cell growth

A

Plate count
membrane filtration
direct count under microscope
turbidity

33
Q

List the 5 main groups of microbes classified according to their temp. range of growth, and what temp they grow at.

A 
Psychrophiles -10 - 20C
Psychotrophs 0-30C
Mesophiles 10-50C
Thermophiles 40-70C
Hyperthermophiles 65-110C

MCR101 (13 decks)

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