How does salmonella invasion occur?
bacterial mediated endocytosis (2 steps)
1) attachment
2) entry
How do salmonella get from the lumen of the gut into the body?
cross the M epithelial cells
cause vili to ruffle and pull it in via phagosome
How does salmonella facilitate entry into M cells? survive phagosomes and macrophages?
type III secretory apparatus
What is the name of the pathogenicity island that most of the virulence factors are found on?
SPI1 (salmonella pathogenicity island)
How does SIP facilitate entry?
SIP proteins sned signal to host cells that changes conformation and causes ruffles and phagocytosis
What does salmonella do to evade lysosomes?
inhibits fusion of phagosomes with lysosome
How does pathogen get from inside cell to mac?
another type III secretory apparatus (exports proteins into macs)
Once inside the macrophage, how does salmonella protect itself?
two component signal transduction
What is a two component transfer system?
has a sensor and a regulator (controls virulence factors)
What is the sensor for salmonella?
histidine autokinase
PhoQ
(phosphodonor)
What is the regulator for salmonella?
aspartate autokinase
PhoP
How does the sensor, histidine autokinase, relay its signal to the response regulator?
transfers phosphate group response regulator
Name 4 examples controlled by 2 component signaling?
1) Chemotaxis (E coli)
2) Pertussis
3) Capsule (pseudomonas aeruginosa)
4) PhoPQ regulon (Salmonella)
What does salmonella sense to tell it it is inside a macrophage?
low magnesium
PhoP phosphorylates in response to this
What genes are upregulated by PhoP?
pag
prg are repressed - they are involved in invasion into M cells
What are prg genes?
PhoP Repressed Genes
needed for entry into M cells, macs
What are pag genes?
PhoP activated genes (needed for survival in macs)
How do you determine this PhoPQ system is necessary in salmonella disease?
delete it and lose virulence
