Module 4 Structure

Question 1

Flagellum Function

Answer 1

Provide Motility

Acts like a propeller.

Question 2

Cell Wall Function

Answer 2

Provides strength to the bacterial cell
Determines Bacterial cell shape
Protects against osmotic lysis.

Question 3

Capsule Function

Answer 3

Protect cell from attack by host’s immune system (phagocytosis)
Prevents bacterial cell from desiccation (drying out)
Aids in bacteria adhering to cell surfaces & structures
Act as a source of nutrients.

Question 4

Fimbriae Function

Answer 4

Attachment (adhesion) of bacterial cells to surfaces.

Question 5

Draw a diagram of a microbial growth curve for a closed batch culture system.

Answer 5

Death/decline phase
Lag phase
Log/exponential phase
Number of living bacterial cells (Log10)
Stationary phase
Time

Question 6

Which phase would a microbiologist use to calculate the fastest doubling time (growth rate) of a bacterium?

Answer 6

Log Exponential Phase

Question 7

By which process do bacteria multiply?

Answer 7

Binary Fission

Question 8

In what phases are the cells most likely to be sensitive to penicillin?

Answer 8

Log Exponential Phase

Question 9

Why are cells sensitive to penicillin in this phase?

Answer 9

Cells are replicating/growing/dividing/ during this phase,

Cell wall being synthesised/turned over.

Question 10

why is a ‘persister’ bacterium insensitive to penicillin treatment?

Answer 10

In a Dormant, non-dividing phase.
Penicillin targets bacteria as they are growing/dividing (and
synthesising cell wall), bacteria that are in this dormant, non-dividing phase are not targeted by penicillin.

Question 11

What are the 3 main things microorganisms need in order to grow?

Answer 11

1. Carbon source (building blocks for macromolecular synthesis)
2. Energy source (energy (electrons) to drive anabolic and catabolic reactions in the cell)
3. Reducing power (carriers of energy/electrons (NAD+
   /NADP+)

Question 12

Carbon source

Answer 12

Building blocks for macromolecular synthesis

Question 13

What is Carbon source?

Answer 13

Building blocks for macromolecular synthesis

Question 14

What is Energy source?

Answer 14

Energy electrons to drive anabolic and catabolic reactions in the cell

Question 15

What is Reducing power?

Answer 15

Carriers of energy/electrons NAD+/NADP+

Question 16

Photoautotroph

• Carbon source
• Energy source

Answer 16

• CO2 (inorganic carbon)

- Light

Question 17

Chemoheterotroph

• Carbon source
• Energy source

Answer 17

• Organic compounds

- Chemical compounds

Question 18

Photoheterotroph

• Carbon source
• Energy source

Answer 18

• Organic compounds

- Light

Question 19

Chemoautotroph

• Carbon source
• Energy source

Answer 19

• CO2 (inorganic carbon)

- Chemical compounds

Question 20

Photoautotroph Examples

• 3 for Oxygenic
• 2 for Anoxygenic

Answer 20

• Plants, algae and cyanobacteria

- Photosynthetic green sulphur and purple sulphur bacteria

Question 21

Chemoheterotroph

• 4 for Aerobic respiration
• 4 for Anaerobic respiration
• 3 for Fermentation

Answer 21

• Animals, fungi, protozoa and many bacteria
• some animals, protozoa, bacteria and archaea
• some bacteria, fungi (yeasts) and archaea

Question 22

Oxygenic photoautotrophs

Answer 22

Carry out photosynthesis aerobically and use H2O to reduce CO2, producing O2 as a by-product.

Question 23

Anoxygenic photoautotrophs

Answer 23

Carry out photosynthesis anaerobically (do not use H2O nor produce O2.
Eg sulphur bacteria use H2S to reduce CO2, producing S as a by-product.

Question 24

Functional food

Answer 24

Food claimed to have a health-promoting or disease-preventing property beyond the basic function of
supplying nutrients.

Question 25

Probiotic.

Answer 25

Live microorganisms which when ingested in adequate amounts confer a health benefit on the host.

Question 26

What types of bacteria are commonly used as probiotics?

Answer 26

Majority of probiotics are Gram positive, lactic acid producers Bifidobacterial species and Lactobacillus species.

Question 27

Draw a diagram depicting the structure of a bacteriophage.

Answer 27

the bacteriophage DNA the tail sheath the head the tail fibres.

Question 28

Lysogenic cycle

Answer 28

Viral genome inserted into the bacterial chromosome and lies dormant, replicating with the bacterial cell and being passed on to all daughter cells until it is induced to leave the chromosome

Question 29

Lytic cycle

Answer 29

Replication cycle that results in cell death and release of phage particles

Question 30

Prophage

Answer 30

Inactive bacteriophage genome inserted into a specific site on a bacterial host cell’s chromosome.

Question 31

FOUR stages of microbial pathogenesis.

Answer 31

- Adherence to host cells - Invasion of host tissues - Replication within host tissues - Disease causing damage to host tissues

Question 32

Adherence - list a bacterial virulence factor - how it contributes to the virulence of the bacteria?

Answer 32

Adhesions – bind to host cell

Question 33

Invasion of host tissues - list a bacterial virulence factor - how it contributes to the virulence of the bacteria?

Answer 33

Motility – move through mucus | Internalin-related proteins (invades host)

Question 34

Replication within host tissues - list a bacterial virulence factor - how it contributes to the virulence of the bacteria?

Answer 34

Siderophores – bind iron | Capsules – resist phagocytosis

Question 35

Disease causing damage to host tissues - list a bacterial virulence factor - how it contributes to the virulence of the bacteria?

Answer 35

Endotoxins – cause inflammation/fever | Exotoxins – can be cytotoxins, neurotoxins, enterotoxins.

Question 36

Selective toxicity - My answer - worksheet answer

Answer 36

Chemical 'magic bullet' to kill microbial cells but not the host cells. Effective antimicrobial agent must be more toxic to a pathogen than to the pathogen’s host. E.g. the antimicrobial agent kills microbial cells without damaging the host cells.

Question 37

Most important cause of genetic diversity in microbial populations.

Answer 37

Mutations

Question 38

Mutations can be

Answer 38

``` Spontaneous (occur randomly) Environmental causes (such as UV light, radiation etc.) ```

Question 39

Draw FIVE key target sites of antimicrobial activity within a bacterium

Answer 39

- Cell wall synthesis (inhibition of peptidoglycan) - Protein synthesis (ribosomes) - Cytoplasmic membrane - Metabolic pathways/metabolites/binding site of proteins or receptors - DNA or RNA synthesis

Question 40

4 Ways to slow or prevent antibiotic resistance from occurring.

Answer 40

- Decrease antibiotic utilization - Improve diagnostics - Identify new targets - Combination therapies

Question 41

Features of the bacterial genome.

Answer 41

- Single circular chromosome. - No nuclear membrane (chromosome restricted to nucleoid). - Plasmids (small, circular, self-replicating DNA molecules).

Question 42

Vertical gene transfer

Answer 42

cells replicate their genomes and pass copies to their daughter cells

Question 43

Horizontal gene transfer

Answer 43

prokaryotes acquire genes from other microbes of the same generation

Question 44

Draw a diagram outlining the stages of an infectious disease.

Answer 44

``` X axis (vertical) = Number of microorganisms or intensity of signs or symptoms Y axis (horizontal) = time Incubation period Prodromal period Illness stage Decline Convalescence ```

Question 45

spread of disease involves six components which must be present for an infection to spread from one person to another (the chain of infection). what are they?

Answer 45

- Causative agent (e.g. bacteria, parasite, virus) - Reservoir/source (e.g. human, animal, fomite, food, water) - Means of exiting the body (e.g. excretions, secretions, droplets) - A mode of transmission to spread the infection (e.g. contact, airborne, vector) - Portal of entering the body (e.g. respiratory, GI, GU, mucous, skin) - A person at risk (e.g. young/elderly, immunocompromised)

Question 46

Infectious diseases can be classified epidemiologically into four categories:

Answer 46

Endemic Sporadic, Epidemic Pandemic.

Question 47

HIV is a retrovirus. Explain what the term retrovirus means.

Answer 47

``` HIV synthesises DNA from its RNA genome. This is reverse (“retro”) of the usual DNA to RNA information flow (Reverse transcription). ```

Question 48

Draw a phylogenetic tree of sequences of a virus taken from different tissues of a single individual. What does the tree tell you about the relationships between the viral genome sequences?

Answer 48

L36 Viruses in each individual tissue are more closely related to each other than they are to viruses from other tissues.

Question 49

Draw a phylogenetic tree of sequences of a virus taken from different tissues of a single individual. How would you explain this pattern of relatedness?

Answer 49

L36 Single viruses infect individual tissues and then remain in those tissues where they evolve.

Question 50

What are the Selection pressures that the HIV virus is under within an individual patient?

Answer 50

The immune system Drug regimen Changes in the receptor Tropism in tissues