Cellular Microbiology and Bacterial Pathogenesis

Question 1

What are distinct features of prokaryotes?

Answer 1

• Absence of distinct nucleus
• DNA is in the form of a single circular chromosome
• Transcription and translation can be carried out simultaneously

Question 2

Who created the first vaccine?

Answer 2

Edward Jenner

Question 3

What is Koch’s postulates?

Answer 3

Important technique for determining the actual microbial cause agent of a disease

Question 4

Who is Alexander Fleming?

Answer 4

Discovered the first antibiotic-penicillin

Question 5

What is the unique parts of gram negative and gram positive bacteria?

Answer 5

Gram - have inner and outer membranes

Gram + have a capsule (polysaccharide)

Question 6

What are the 5 groups of bacteria?

Answer 6

1. Spherical- strep
2. Rod (bacilli)- salmonella
3. Spiral (spirilla) - H. Pylori
4. Comma- V. Chlolera
5. Corkscrew- Trepona palidum

Question 7

What is the function of adherence factor?

Answer 7

Binding to host cells, will determine the site of colonisation. some diseases can target different areas depending on adherence factor

Question 8

What are the functions of cell wall components?

Answer 8

Inhibit phagocytosis, escape from immune recognition, escape complement

Question 9

What is the role of invasion factors?

Answer 9

Mediate entry into host cells

Question 10

What is an endotoxin? What does it do?

Answer 10

A toxin that is attached to the wall of bacteria. Activates PRR (TLR4)> pro-inflammatory cytokines

Question 11

What happens at high concentrations of endotoxins?

Answer 11

Septic shock

Question 12

What do exotoxins do and what can it lead to?

Answer 12

Makes holes in membranes. hemolytic= causes lysis of red blood cells and kills other cells

Question 13

What is salmonella?

Answer 13

• Foodbourne gram- rod
• different strains cause diff diseases in diff animals
• typhoid fever, food poisoning
• uses 2 type III secretion systems encoded on pathogenicity islands
• SPI-1 involved in invasion and inflammation

Question 14

What is the salmonella enterica lifecycle?

Answer 14

• replicates within a membrane bound vacuole
• They promote the multiplication of bacteria in epithelial cells and macrophages
• Help bacteria counteract immune signalling

Question 15

What is shigella?

Answer 15

Infection through ingestion of contaminated food or water, low inoculum.

• Induces its own uptake into epithelial cells from basal side using T3SS
• Shigella replicates rapidly in cytosol
• Actin comet tail to move within cells and from cell to cell

Question 16

What is pathogenic E.coli?

Answer 16

• EPEC and EHEC are best studied
• Infection through contaminated food and water
• Gram -ve, extracellular
• Virulence is located on lotus of enterocyte effacement PAI

Question 17

Why do bacteria target the actin cytoskeleton?

Answer 17

To:

• Promote entry into non-phagocytic cells
• Inhibit entry or phagocytosis in macrophages
• Move from cell to cell to spread infection
• Adhere tightly to cells

Question 18

What do bacteria target in the cell?

Answer 18

Actin cytoskeleton

Question 19

What is actin?

Answer 19

The skeleton and muscle of the cells, it enables: cell mobility, cell junction and cell shape etc

Question 20

What is actin polymerization?

Answer 20

A reversible process in which monomers both associate and dissociate from ends of actin filaments

Question 21

What do GTPase activating proteins do?

Answer 21

Catalyse GTP hydrolysis by the GTPase> this inactivates the protein

Question 22

What do GTPase activating proteins do?

Answer 22

Catalyse GTP hydrolysis by the GTPase> this inactivates the protein

Question 23

What are phagocytes?

Answer 23

Cells that protect the body by ingesting harmful bacteria and dead or dying cells by phagocytosis

Question 24

What are the steps of phagocytosis?

Answer 24

• Binding
• Internalisation
• Degradation

Question 25

What is actin regulated by?

Answer 25

• Rho GTPases
• WASP family proteins
• The Arp2/3 complex

Question 26

What drives phagocytosis?

Answer 26

Actin

Question 27

What are the different modes of entry by bacteria?

Answer 27

1. Receptor driven- zipper, small actin rearrangements (listeria)
2. Type III secretion system- trigger mechanism, large actin ruffles (salmonella, shigella)

Question 28

How does yersinia enter the cell?

Answer 28

Yersinia needs to enter the host through invasion of epithelial cells, then it remains extracellular.

• yersinia has a T3SS but doesn’t use it for entry
• Uses adhesions, especially invasin
• Invasin binds β1 integrins

Question 29

What is actin based motility?

Answer 29

Actin-based motility propels the bacteria through the cytosol and enables spread into neighbouring cells
used by: shigella, listeria, rickettsia

Question 30

How is actin based motility carried out by shigella?

Answer 30

Vacuole rupture initiated by IpaB

recruits N-WASP and then binds Arp2/3

Question 31

What do bacterial virulence factors mimic?

Answer 31

Host factors like GEFs and GAPs and activate host actin polymerisation pathways

Question 32

What are pattern recognition receptors?

Answer 32

Pattern recognition receptors recognise pathogen associated molecular patterns or danger/damage associated molecular patterns
-this initiates signal transduction cascades that induce the expression and production of response genes