Week 5: Virulence and Vibrio 2 - Vibrio and regulation of virulence factors

Question 1

What is the final feature of Gram-negative bacteria and virulence?

Answer 1

Regulation of virulence factors and related processes critical → correct time and place

Question 2

Why is Regulation of virulence factors and related processes critical?

Answer 2

processes critical → correct time and place

ensure virulence genes are only turned on when the vibrio are in the appropriate region of the small intestine.

CT and TCP are co-ordinately regulated

Question 3

What does the regulation of virulence factors and related processes typically involve?

Answer 3

integration of many environmental signals

Question 4

What are examples of environmental signals detected by regulators in the regulation cascade?

Answer 4

presence of bile

temp

pH

Question 5

What are the 2 primary virulence factors?

Answer 5

CT
TCP

Question 6

What is the pathway for TCP activation from environmental signals?

Answer 6

bile –> TcPH & ToRS –> ToxT –> TcpA-F

–> TCP

Question 7

What is the pathway for CT activation from environmental signals?

Answer 7

bile etc –> TcPH & ToRS –> ToxT –> CtxAB

–> CT

Question 8

How does Vibrio coordinate expression of virulence genes with biofilm formation?

Answer 8

master regulator AphA

Activates expression of VpsT.

activates expression of the VpsA operon (form the biofilm polysaccharide)

Activates expression of the biofilm matrix proteins RbmC and Bap1.

Promote biofilm formation.

Question 9

What does AphA regulate?

Answer 9

TCP

CT
biofilm formation

Question 10

What is the positive feedback loop in biofilm formation?

Answer 10

VpsT activates VpsR and vice versa.

Then activate the downstream proteins/ operons.

Question 11

How do virulence and biofilm formation co-regulate?

Answer 11

via AphA

Question 12

How else can bacteria regulate their virulence factors?

Answer 12

cell density

using quorum sensing

Question 13

How can vibrio detect cell density?

Answer 13

quorum sensing

Question 14

When are biofilm, TCP and CT genes upregulated?

Answer 14

low cell density

Question 15

At what cell density does V. cholerae establish infection?

Answer 15

low cell density.

not many cells in host to establish pathogenicity

Question 16

What regulators establish/ promote AphA and VpsT?

Answer 16

low cell density promotes CqsT and LuxPQ sensors.

These sensors lead to phosphorylation f LuxU and LuxO, leading to activation of Qrr1-4 sRNAs.

And lead to AphA

Question 17

In high cell density, what regulator inhibits biofilm, TCP and CT?

Answer 17

HapR

Question 18

What does HapR/Hap promote?

Answer 18

At high cell density, production of virulence factors and biofilm repressed, production of Hap protease increased

→ dispersal and escape of large number of cells from the host and back out into the environment.

Question 19

What 2 autoinducers does V. cholerae make?

Answer 19

Vibrio-specific CAI-1
and AI-2

Question 20

When does Vibrio’s autoinducers accumulate?

Answer 20

high cell density

Question 21

What sensing protein attaches CqsS?

Answer 21

CAI-1

Question 22

What sensing protein attaches LuxPQ?

Answer 22

AI-2

Question 23

What do the autoinducers mean for downstream components?

Answer 23

dephosphorylation of LuxU and LuxO

no longer expression of sRNAs.

small RNAs canno longer inhibit expression of HapR.

HapR can repress biofilm genes and upregulate expression of the Hap protease

Question 24

What other regulators can feed into the network via environmental signals?

Answer 24

cAMP, increase HapR expression

8 DGCs can promote c-di-GMP and upregulate VpsR and promote biofilm formation.

7 PDEs inhibit c-di-GMP and inhibit biofilm formation