Virulence and Phagocytes

Question 1

Siderophores

Answer 1

substances produced by bacteria to capture iron from the host

Question 2

Exotoxins

Answer 2

~ actively secreted proteins

~ act on specific targets

Question 3

Endotoxins

Answer 3

~ bound to cell
~ released when bacteria lyse
~ indirect action, activated host systems which cause damage
~ lipopolysaccharide in outer cell wall of gram -ve cells

Question 4

Name the five invasins.

Answer 4

Hyaluronidase
Neuraminidase 
Collagenase
Coagulase
Strephtokinase/Staphylokinase

Question 5

Name the different adhesins. (7)

Answer 5

Flagella
Pili
Fimbrae
Stallks
Lipoteichoic acid
Adherence proteins
Capsule

Question 6

Bacterial superantigens

Answer 6

~ stimulate large numbers of immune cells

~ damage by extensive inflammatory response

Question 7

Cytolytic toxins

Answer 7

attack cell constituents, causing lysis

Question 8

A-B toxins

Answer 8

two subunits (A + B)
B = binds to cell surface receptor
A = transported to cytoplasm + interfere with cell's functions

Question 9

Corynebacterium diptheriae

Answer 9

~ upper respiratory tract infection
~ high mortality (5-10%)
~ exotoxin (diphtheria toxin) is encoded by temperate phage DNA (tox gene)
~only lysogenic bacterial cells produce the toxin

Question 10

How does the cholera toxin work?

Answer 10

A-5B
~ A subunit increases adenylate cyclase activity
= increase cAMP
= loss of cell nutrients
= diarrhoea

Question 11

Amoebae are described as … and can only …

Answer 11

a natural analogy

feed on attached bacteria

Question 12

Roles of molecular chaperones are..

Answer 12

~ correct folding of polypeptide

~ re-fold incorrectly-folded proteins

Question 13

Normal sigma factor

Answer 13

sigma 70

Question 14

QS

Answer 14

quorum sensing

= taking signals from other species and using them to turn on genes

Question 15

Egested bacteria

Answer 15

~ still be in the stress response = increased antimicrobial resistance
~ close association in food vacuole = hot-spot for genetic exchange
~ increase in QS controlled genes = increase in virulence

Question 16

Entner-Doudoroff pathway

Answer 16

~ provides cells with an alternative to glycolysis for fermenting sugars
~ the cells can maximize the production of reducing power at the expense of ATP production

Question 17

Elastase

Answer 17

lyses collagen and fibronectin

Question 18

Alkaline protease

Answer 18

lyses fibrin

Question 19

Pyocyanin

Answer 19

~ inhibits cilia
~ disrupts epithelial cellas
~ starts an inflammatory response in phagocytes

Question 20

Leukacidin

Answer 20

a cytotoxin pore-forming toxin

Question 21

Haemolysin

Answer 21

lyses erythrocytes by forming pores in the phospholipid bilayer OR hydrolysing bilayer phospholipids

Question 22

Type III secretion system (T3SS)

Answer 22

~ employed by gram -ve pathogens

~ injects effectors directly into the cytoplasm of eukaryotic cells

Question 23

ExoU

Answer 23

~ one of the most aggressive toxins inject by T3SS = rapid cell necrosis
~ Pseudomonas aeruginosa uses it

Question 24

Phospholipase C

Answer 24

enzymatic attack of phospholipid bilayer

Question 25

Lecithinase

Answer 25

phospholipase that degrades lecithin (a.k.a. phosphatidylcholine)