Regulation of Virulence Salmonella

Question 1

State why S. typhimurium infection of mice is a good experimental model for S. typhi infections of humans

Answer 1

S. typhimurium in mice minics the disease caused by S. typhi in humans

Question 2

Describe acid tolerance and its role in virulence

Answer 2

Acid shock proteins

They are considered virulence factors in that they help the bacteria survive

Question 3

Describe the S. typhimurium process of invasion

Answer 3

INTRACELLULAR PATHOGEN
Uses type III secretory apparati to inject signal to M cells (in gut) to ruffle and phagocytize the bacteria into a phagosome. Salmonella inhibits fusion of the phagosome with lysosomes

Lack of phagosome-lysosome fusion allows the bacterial cell to transit (via the phagosome) through the M cell where it interacts with macrophage. There is a second Type III secretary system that injects bacterial proteins into the macrophage to facilitate phagocytosis

Question 4

Describe the phoP-phoQ signal transduction pathway and its regulon

Answer 4

PhoQ is membrane bound histidine kinase sensor (senses low Mg)

PhoP is its cognate response regulator that functions as DNA-binding protein. When phosphorylated it represses genes required for invasion into M cells and macrophages (prg) while activating genes required for survival in the macrophage (pag)

Question 5

Two-component signal transduction

Answer 5

Sensor: histidine autokinase, usually a membrane bound receptor that autophosphorylates (ATP donor) on a histidine residue

Response regulator: aspartate autokinase, usually a DNA binding protein that autophosphorylates on asparate reside (pSensor is phospho-donor). Either can activate or repress and is attached to an output domain (DNA binding domain)