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MICR2209 > 14 - Intro to Bacteriology > Flashcards

14 - Intro to Bacteriology Flashcards

1
Q

Bacteria prokaryotes or eukaryotes

A

Prokaryotes

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2
Q

Aechaea prokaryotes or eukaryotes

A

Prokaryotes

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3
Q

Eukarya prokaryotes or eukaryotes

A

Eukaryotes

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4
Q

Universal phylogenetic tree

A

shows evolutionary relationships based on 16S rRNA sequence comparisons

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5
Q

Bacteria

A
  • single-celled
  • Cell walls contain peptidoglycan
  • no membrane-bound nucleus
  • no membrane-bound organelles
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6
Q

Smallest bacterium

A

Mycoplasma (0.3 μm diameter)

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7
Q

Most common shapes of bacteria

A

Coccus (cocci) and rods (bacillus/bacilli)

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8
Q

Function of capsules and smile layers

A

Resistance to phagocytosis, adherence to surfaces

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9
Q

Fimbriae and pili function

A

Adherence to surfaces, DNA transfer, twitching and gliding motility

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10
Q

Flagella function

A

Swimming and swimming motility

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11
Q

Endospore function

A

Survival under harsh conditions

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12
Q

What colour do gram positive bacteria stain

A

Purple

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13
Q

What colour do gram negative bacteria stain

A

Pink or red

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14
Q

Gram positive cell envelope

A
  • Cell wall is thick, multi layered peptidoglycan containing teichoic acids
  • Plasma membrane
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15
Q

Gram negative cell envelope

A
  • Cell wall is a thin peptidoglycan layer
  • Large periplasmic space between outer and inner membranes
  • Outer membrane containing lipopolysaccharides (LPS)
  • Plasma membrane
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16
Q

Why does gram positive stain purple

A

Thick cell wall traps crystal violet

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17
Q

Why does gram negative stain pink

A

Cell wall cant hold crystal violet and is washed away by alcohol and counter stained with safranin

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18
Q

Flagella

A
  • Mediate swimming bacterial motility (flagella rotate to propel the bacteria forward)
  • helical proteinaceous structures extending from the plasma membrane and
    cell wall
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19
Q

Polar flagella

A

Flagella at one or both ends of a cell

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20
Q

Peritrichous flagella

A

Flagella spread over the whole surface of the cell

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21
Q

Pili / Fimbriae

A
  • proteinaceous structures extending from the plasma membrane and cell wall
  • Thinner, shorter, straighter than flagella
  • Mediate attachment of bacteria to surfaces including host cells
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22
Q

Sex pili

A

Mediate the transfer of DNA from cell to cell

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23
Q

Type IV pili

A

mediate twitching motility by extending and retracting to
pull the cell forward

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24
Q

Endospores

A
  • Heat and chemical resistant
  • Radiation resistant
  • Dormant
  • Thick-walled
  • Develop within the vegetative (mother) cells of some species
25
Q

Examples of genus that produce endospores

A

Bacillus and Clostridium

26
Q

Bacterial growth

A

Logarithmic or exponential (number doubles at each generation)

27
Q

Generation time (g)

A

The time for a cell to
produce 2 cells or the time for a bacterial population to double in number

28
Q

Generation time of E.coli

A

g = 20 mins

29
Q

Mycobacterium tuberculosis

A

g = ~ 12 hours

30
Q

Factors that limit bacterial growth

A
  • Nutrients are used up
  • Metabolic wastes accumulate
  • Living space may become limited
  • Aerobes may suffer from oxygen depletion
31
Q

Four main phases of bacterial growth curve

A
  • Lag phase
  • Exponential or log phase
  • Stationary phase
  • Death phase
32
Q

Lag phase

A

synthesis of new components, preparing to divide

33
Q

Log or exponential phase

A

growth at maximal growth rate possible

34
Q

Stationary phase

A

Total number viable bacteria constant

35
Q

Causes of stationary phase

A
  • Balance between cell division and cell death
  • Nutrient or O2 limitation
  • Accumulation of toxic by products
36
Q

Obligate aerobe

A
  • Depend on atmospheric O2
    for growth
  • Gain energy by respiration
37
Q

Microaerophile

A

Require 2-10% oxygen (lower than atmospheric)

38
Q

Facultative anaerobe

A

Do not require O2 but grow better in its presence

39
Q

Aerotolerant anaerobe

A

Grow equally well in presence or absence of O2

40
Q

Obligate anaerobe

A

Killed by O2 (may gain energy by fermenting sugars)

41
Q

Bacterial pathogen O2 requirement

A

Helps decide which body site is targeted

42
Q

Mesophile

A

Moderate temperature (20-45ºC)

43
Q

Psychrophile

A

Cold loving (15ºC)

44
Q

Thermophile

A

Heat loving (60ºC)

45
Q

Hyperthermophile

A

Extremely thermophilic (found in ocean hydrothermal vents at 85-100ºC)

46
Q

Which temperature group do most human pathogens belong to

A

Mesophiles as human body temp constant 37ºC

47
Q

Acidophile

A

0 - 5.5 pH

48
Q

Neutrophile

A

5.5 - 8 pH

49
Q

Alkaliphile / alkalophile

A

8 - 11.5 pH

50
Q

Which pH group do most human pathogens belong to

A

Neutrophiles but there are some important exceptions

51
Q

what is the culture media for bacteria determined by

A
  • Sources of carbon, electrons and external energy used for growth
  • The diversity of chemicals needed to make bacterial cell components
  • The need for growth factors (e.g. vitamins, amino acids)
52
Q

Two common methods of culturing bacteria

A
  • Liquid culture: Bacteria grown as a liquid suspension (‘broth culture’)
  • Solid culture: Bacteria grown on an agar suface (‘plate culture’)
53
Q

Types of culture media

A
  • Complex media
  • Selective media
  • Differential media
54
Q

Complex media

A
  • Contain some ingredients of unknown chemical composition
  • May include peptones, meat extract, yeast extract, blood
  • Useful as many bacteria can grow on them
55
Q

Examples of complex media

A

Nutrient agar, TSA, blood agar, MacConkey agar

56
Q

Selective media

A

allow the growth of some bacteria while inhibiting others

57
Q

Differential media

A

distinguish between different bacteria and may allow tentative identification

58
Q

How is MacConkey agar both selective and differential

A
  • Bile salts and crystal violet inhibit Gram positive bacteria but not Gram negative bacteria
  • Lactose and neutral red, a pH indicator, differentiate lactose fermenters (pink) from non-fermenters (colourless)

MICR2209 (26 decks)

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