Myco. tuberculosis

Question 1

Explain the infectious lifecycle of Mtb

Answer 1

Mtb is aerosolised, goes in the lung (alveola) and interacts with macrophages.

Question 2

what is the granuloma?

Answer 2

It then passes through the alveolar barrier and migrates to the lymph nodes. The macrophages will recruit B and T cells. This makes a ball. There is a lot of secretion of inflammation factors.

Question 3

What do the 4 antibiotics do?

Answer 3

Mostly inhibits cell wall fromation. One inhiibits RNa polymerase

Ethanbutol: disrupts cell wall formation (disrupts Lam formation)

Question 4

MDR = multidrug resistant Tb
XDR = extensively drug-resistant.

Answer 4

. Resistant to at least Ryph. And Iso.
Resistant to Ryph, Iso, fluoroquinones and 1 injectable second-line drug

Question 5

cell wall architecture of Mtb.

Answer 5

–. It contains 1 plasma membrane.
Small peptidoglycan layer. Second membrane, made of mycolic acids and glycolipids (thick).

There is porins. There is Lam (glycolipid) connected to the cell membrane.

Question 6

What does 2nd membrane of Mtb do?

Answer 6

This layer prevents antibiotics from happening and resistants chemical damage.

Question 7

Ways to study bacterial virulence (in…)

Answer 7

Vitro = what happens to cell
vivo = study disease

Question 8

Bacetrial load

Answer 8

How many bacteria are alive? Shown in CFU

Question 9

Most genes in bacteria are found in

Answer 9

Operons. makes it hard to see which protein is cause of bacterial virulence

Question 10

How do we do the experiments?

Answer 10

Knock out what we think is a virulence gene. CFU should decrease.

Reintroduce the gene back in.

If expression comes back, it’s THIS gene that’s responsible.

If the expression DOSEN’T come back, it’s due to OTHER genes in the operon. This is called a polar effect

Question 11

What are cell wall glycolipids?

Answer 11

virulence factors. They are LamMan and TDM

Question 12

How does phaogytsis usually occur?

Answer 12

IgG connects with opsonized bacteria. Recognised by cell, phagocytosed, fuses with lysosomes to get killed.

Question 13

What does TDM do?

Answer 13

TDM affects granuloma formation

It interacts with Mincle to express inflammation factors and other things so that the bacteria is not killed

It also inhibits phagosome maturation

Question 14

What does LamMan do?

Answer 14

It inhibits apoptosis, as cell death is a really important factor for survival in Tb.

LamMan changes how phagocytosis is done as the bact. Enters through a mannose receptor. This makes it so the bacteria block calcium signalling, which blocks phagosome maturation.

Question 15

Name at least two virulence factors

These virulence facots prevent fusion with lysosomes

Answer 15

PtpA and SapM

Question 16

How does PtpA work? (2 purposes)

Answer 16

It prevents phagosome acidification that leads to phagosome maturation. It does this by targeting and binding the subunit H of the vacuolar ATPase pump.
It also dephosphorylates host vacuolar sorting protein VPS33B.
To work, PtpA must have its catalytic domain (to VPS) and binding domain (to subunit H).

Question 17

How does SapM work?

Answer 17

Phosphatase (desphosphorilate PI3P), a lipid.

Is a key lipid on the membrane of the phagosome TO ALLOW FUSION TO HAPPEN.

Desphosphoriliation by SapM = no more progression of phagocytosis. Some studies show that there might be some polar effects, as COMP is not as good as WT.

Question 18

Does Mtb escape from the phagosome ?

Answer 18

cytosol through the T7SS ESX-1 secretion system.

Question 19

Pros and cons of Mtb escape?

Answer 19

Pros: More nutrients, escape from lysosome, host-cell death, dessimination
Cons: Inflammatory response, autophagy, cytosolic surveillance

Question 20

When does Mtb want to start necrosis?

Answer 20

TB does stay inside, so it prevents apoptosis. But at some point it will try and escape when it has replicated enough TB must initiate necrosis to escape. Necrosis is good for bacteria to escape and infects other cells.

Question 21

Does Mtb produce an endotoxin or exotoxin?

Answer 21

Exotoxin, C-terminal of porin - CpnT

Question 22

What does the exotoxin TnT do?

Answer 22

Cleaves NAD+

Question 23

How is Mtb protected by it’s own TnT?

Answer 23

Operon control of TnT as well as IFT (no NAD destruction)