14 - Intro to Bacteriology

Question 1

Bacteria prokaryotes or eukaryotes

Answer 1

Prokaryotes

Question 2

Aechaea prokaryotes or eukaryotes

Answer 2

Prokaryotes

Question 3

Eukarya prokaryotes or eukaryotes

Answer 3

Eukaryotes

Question 4

Universal phylogenetic tree

Answer 4

shows evolutionary relationships based on 16S rRNA sequence comparisons

Question 5

Bacteria

Answer 5

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

Question 6

Smallest bacterium

Answer 6

Mycoplasma (0.3 μm diameter)

Question 7

Most common shapes of bacteria

Answer 7

Coccus (cocci) and rods (bacillus/bacilli)

Question 8

Function of capsules and smile layers

Answer 8

Resistance to phagocytosis, adherence to surfaces

Question 9

Fimbriae and pili function

Answer 9

Adherence to surfaces, DNA transfer, twitching and gliding motility

Question 10

Flagella function

Answer 10

Swimming and swimming motility

Question 11

Endospore function

Answer 11

Survival under harsh conditions

Question 12

What colour do gram positive bacteria stain

Answer 12

Purple

Question 13

What colour do gram negative bacteria stain

Answer 13

Pink or red

Question 14

Gram positive cell envelope

Answer 14

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

Question 15

Gram negative cell envelope

Answer 15

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

Question 16

Why does gram positive stain purple

Answer 16

Thick cell wall traps crystal violet

Question 17

Why does gram negative stain pink

Answer 17

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

Question 18

Flagella

Answer 18

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

Question 19

Polar flagella

Answer 19

Flagella at one or both ends of a cell

Question 20

Peritrichous flagella

Answer 20

Flagella spread over the whole surface of the cell

Question 21

Pili / Fimbriae

Answer 21

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

Question 22

Sex pili

Answer 22

Mediate the transfer of DNA from cell to cell

Question 23

Type IV pili

Answer 23

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

Question 24

Endospores

Answer 24

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

Question 25

Examples of genus that produce endospores

Answer 25

Bacillus and Clostridium

Question 26

Bacterial growth

Answer 26

Logarithmic or exponential (number doubles at each generation)

Question 27

Generation time (g)

Answer 27

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

Question 28

Generation time of E.coli

Answer 28

g = 20 mins

Question 29

Mycobacterium tuberculosis

Answer 29

g = ~ 12 hours

Question 30

Factors that limit bacterial growth

Answer 30

- Nutrients are used up - Metabolic wastes accumulate - Living space may become limited - Aerobes may suffer from oxygen depletion

Question 31

Four main phases of bacterial growth curve

Answer 31

- Lag phase - Exponential or log phase - Stationary phase - Death phase

Question 32

Lag phase

Answer 32

synthesis of new components, preparing to divide

Question 33

Log or exponential phase

Answer 33

growth at maximal growth rate possible

Question 34

Stationary phase

Answer 34

Total number viable bacteria constant

Question 35

Causes of stationary phase

Answer 35

- Balance between cell division and cell death - Nutrient or O2 limitation - Accumulation of toxic by products

Question 36

Obligate aerobe

Answer 36

- Depend on atmospheric O2 for growth - Gain energy by respiration

Question 37

Microaerophile

Answer 37

Require 2-10% oxygen (lower than atmospheric)

Question 38

Facultative anaerobe

Answer 38

Do not require O2 but grow better in its presence

Question 39

Aerotolerant anaerobe

Answer 39

Grow equally well in presence or absence of O2

Question 40

Obligate anaerobe

Answer 40

Killed by O2 (may gain energy by fermenting sugars)

Question 41

Bacterial pathogen O2 requirement

Answer 41

Helps decide which body site is targeted

Question 42

Mesophile

Answer 42

Moderate temperature (20-45ºC)

Question 43

Psychrophile

Answer 43

Cold loving (15ºC)

Question 44

Thermophile

Answer 44

Heat loving (60ºC)

Question 45

Hyperthermophile

Answer 45

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

Question 46

Which temperature group do most human pathogens belong to

Answer 46

Mesophiles as human body temp constant 37ºC

Question 47

Acidophile

Answer 47

0 - 5.5 pH

Question 48

Neutrophile

Answer 48

5.5 - 8 pH

Question 49

Alkaliphile / alkalophile

Answer 49

8 - 11.5 pH

Question 50

Which pH group do most human pathogens belong to

Answer 50

Neutrophiles but there are some important exceptions

Question 51

what is the culture media for bacteria determined by

Answer 51

- 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)

Question 52

Two common methods of culturing bacteria

Answer 52

- Liquid culture: Bacteria grown as a liquid suspension ('broth culture') - Solid culture: Bacteria grown on an agar suface ('plate culture')

Question 53

Types of culture media

Answer 53

- Complex media - Selective media - Differential media

Question 54

Complex media

Answer 54

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

Question 55

Examples of complex media

Answer 55

Nutrient agar, TSA, blood agar, MacConkey agar

Question 56

Selective media

Answer 56

allow the growth of some bacteria while inhibiting others

Question 57

Differential media

Answer 57

distinguish between different bacteria and may allow tentative identification

Question 58

How is MacConkey agar both selective and differential

Answer 58

- 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)