Bacteria Flashcards
Type 3 secretion system example
Salmonella
Type 3 secretion system components
Basal body (crosses bacteria membranes)
Needle (crosses space between bacterial cell and host membrane)
V-tip complex (crosses the host membrane)
Translocation
substance (bacterial effectors) moved from bacterial cell to host cell
Secretion
substance simply secreted from bacterial cell
Salmonella enterica causes…
food poisoning (most commonly)
Salmonella typhi causes…
typhoid fever
Types of type 3 secretion in Salmonella
Two different pathogenicity islands
SPI-1 & SPI-2
Different niches, induced by different stimuli
SPI-1 invasion and establishment
SPI-2 after invasion for translocation of effector proteins fr survival and replication
Which serotypes of Salmonella can only affect humans?
S. typhi
S. paratyphi
Distinctive features in exclusively human-infective Salmonella
presence of a capsule presence of the typhoid toxin more pseudogenes longer incubation tryptophan and cysteine auxotrophy
Marker of host specific Salmonella serotypes
presence of high number of pseudogenes
Type 3 secretion system pseudogenes in S.typhi
sopA, sopE2, sopD2, slrP
How do type 3 secretion system pseudogenes in S.typhi restrict it to humans?
mouse macrophages can destroy vesicle with Rab32-BLOC-3 dependent antimicrobial pathway
Rab32 would have been blocked by functional versions (sopD2 and GtgE absent in S. typhi)
Roles of membrane proteins in bacterial survival (basic)
Sensing Transport Defence Stress Response Attachment Infection
Bacterial membrane sensing example
2 component systems
Sensor histidine kinase (HPK) & response regulator (RR)
HPK - senses change in environment - often external to cell/membrane
located
HPK autophosphorylated by ATP → HPK-P on conserved His
HPK-P phosphorylates RR → RR-P + HPK
RR-P binds to DNA or to protein and changes cell behaviour
Bacteria membrane transport and defence example
CusCBA
CusCBA (effluxes copper accumulated in periplasm)
Adaptor protein-mediated metal-responsive dynamic assembly–disassembly
model of CusCBA complex.
Two transporters - one on each membrane
- stress = linking protein and transport
- no stress = un-linked no transport
Bacteria membrane stress response example
CpxAR and sigmaE
sigmaE response bacteria
Stress response
Activity of σE is negatively controlled by anti-sigma factor RseA (inner membrane protein)
- held by it and when it is cleaved -> response
Many stress conditions activate σE pathway – all proposed to lead to
accumulation of outer membrane proteins -> signal via DegS protease
CpxAR response bacteria
two-component
Responds to envelope stress conditions - inner membrane protein
Eg alkaline pH, adhesion,
pathogenesis
