Bacteriology - cellular invasion Flashcards
(201 cards)
1
Q
Chlamydia binding
A
Probably many receptors. cell-surface exposed PDI may be bound by EB and have an enzymatic role in entry.
2
Q
Chlamydial entry - actin rearrangements.
A
Requires Rac1 dep remodelling.
3
Q
Chlamydial Rac1 remodelling
A
Injection of Tarp, phosphorylation –> recruitment of Sos and Vav (Rac1 GEFs) and Abi-1 –> WAVE complex activity –> Arp2/3.
Possible role for Ct694.
4
Q
Chlamydial transition EB –> RB
A
EB outer proteins are cross-linked. Disulphide bonds are reduced on internalisation –> nucleoid decondensation –> transcription.
5
Q
Chlamydial effector secretion system.
A
T3SS
6
Q
Chlamydial effectors inserting into inclusion membrane are called…
A
Inc
7
Q
Inc-recruited proteins
A
Rab1, 4, 11; recycling endosome and Golgi related Rab GTPases.
Dynein for transport to perinuclear regions.
8
Q
Chlamydial inclusion body formation and nutrient delivery.
A
Needs lipids (sphingolipids, cholesterol) for development.
a) Golgi fragmentation
b) Multivesicular bodies
c?) Non-classical routes e.g. lipid droplets
9
Q
Inhibition of host cell death: Chlamydia.
A
Early block, late induction
10
Q
Chlamydia: early block of apoptosis.
A
Stabilises inhibitor of apoptosis proteins.
Sequesters pro-apoptotic BAD.
Degrades BH3 only proteins. –> less Bax activation –> less cyt c release.
11
Q
Intracellular bacteria - host cell death.
A
Inhibition - early chlamydia
Induction - late chlamydia, salmonella, shigella
12
Q
Chlamydia - general
A
obligate intracellular pathogen.
13
Q
Intracellular bacteria rapidly escaping cell cytoplasm.
A
Shigella, Listeria
14
Q
Intracellular bacteria remaining withing the membrane bound vesicle.
A
Salmonella, Legionella pneumophila, Brucella abortus or Chlamydia spp
15
Q
Chlamydial target cells
A
Epithelial cells.
16
Q
Chlamydial entry sites
A
Occur at lipid microdomains.
17
Q
Bacteria using raft-dependent entry pathways.
A
Shigella flexneri, Fim H-expressing E. coli, Brucella spp. and Chlamydia spp.
May confer special properties to the early inclusion/vesicle.
18
Q
Chlamydial entry overview.
A
Adhesins, lipid microdomains, actin cytoskeleton reorganisation.
19
Q
Intracellular bacteria uptake
A
Zipper, trigger, other mechanisms, phagocytosis.
20
Q
Intracellular survival
A
Bacterial developmental transition.
Stay in the vacuole?
Manipulating the host cell
21
Q
Manipulating the host cell
A
Bacteria containing compartment interacting with other compartments.
Altering host cell death
Inhibiting immune response.
22
Q
Exiting the host cell
A
Host cell death.
Exocytosis.
Intracellular spread.
23
Q
Host endocytotic pathway
A
Endocytosis/macropinocytosis –> EE –> late endosomes and acidification –> lysosomes.
24
Q
Zipper mechanism
A
Express surface proteins.
25
Trigger mechanism
Inject effector proteins.
26
Result of chlamydial transition to RB.
New effectors by T3SS system.
| Some insert into membrane - Incs.
27
Chlamydia inhibiting immune response
Block nuclear translocation of NFkB.
| Increase NFkB degradation.
28
Inhibiting the immune response - mechanisms
Alter TLR binding
Alter NFkB
Alter cytokine mRNAs
Avoid autophagy.
29
Chlamydial cell escape
Transition from RB to EB and exit by host cell death.
30
Endocytic pathway. Endocytosis-->early endosomes.
Decrease inclusion of normal endocytic ones.
| Use bacterial proteins to recruit Rabs (Chlamydia).
31
Endocytic pathway. EE --> LE.
GTPase Rab5 does this. Recruits EEA1
32
Endocytic pathway. LE --> lysosomes, mechanism
Calcium fluxes.
33
Endocytic pathway. LE --> lysosomes, mechanism; calcium fluxes.
Important in signalling maturation of lysosome. Ca++ influences calmodulin recruits Rab5 recruits PI3P
- ->EEA1
- -> v-ATPases
- -> hydrolases.
34
Inhibiting Ca++ induced lysosomal fusion.
Unknown mechanism by cord factor. (TB).
| Inhibited by phosphatidylinositol derivatives e.g. LAM.
35
LAM full name.
lipoarabinomannan
36
LAM action
Inhibits Ca++ mediated fusion; reduces development to a late endosome or acidification even if just on beads. With mannose caps inhibits recruitment of EEA1 as well.
37
Lysosomal conditions
Acidification via v-ATPase.
Acid hydrolases
Phagolysosomal oxidative burst.
38
Ways to survive acidification of lysosome.
TB: stop this.
| Survive and divert hydrolases: Coxiella.
39
Coxiella survival of lysosome
Coxiella (passively continues down endosomal pathway until this point). Even just 5 minutes after internalisation it acidifies. Delayed acquisition of lysosomal enzymes such as cathepsin D.
40
How many acid hydrolases are there?
About 60.
41
Which bacteria decrease presence of acid hydrolases?
TB (none)
| Salmonelal (very few, and few of their receptor, mannose-6-phosphate).
42
Mechanism of oxidative cell burst.
NADPH oxidase complex recruited by Rac (a Rho GTPase). Electron transfer occurs from NADPH to FAD to oxygen to make superoxide anions of various sorts.
43
Inhibiting oxidative cell burst
Superoxide dismutase by many pathogens.
| Interfere with assembly/recruitment of NADPH oxidase.
44
Interfering with NADPH oxidase.
A phagocytophilum
Listeria
Salmonella
45
General intracellular replication points
```
Use conditions to stimulate replication.
Accumulation of nutrients.
Space limitations
Alteration of vacuolar structure.
Salmonella-induced filaments.
```
46
Space limitations in vacuole.
Acquisition of more lipids expands envelope of organelle.
47
Chlamydia Golgi fragmentation
Necessary for nutrient delivery.
Cleavage of Golgin-84 by CPAF gives access to sphingolipids by Golgi fragmentation. Formation of mini-stacks around the inclusion, triggers re-differentiation into EBs.
48
Interacting with other compartments - necessary for replication: delivery of nutrients.
Chlamydial Golgi-fragmentation.
| Host proteins to facilitate accumulation.
49
Altering vacuolar structure for replication.
• Recruitment of mitochondria and ribosomes causes formation of ER like structure in which bacteria replicate (Legionella). Effector proteins via Dot/Icm.
50
Recruiting autophagy pathway for replication?
Coxiella. Autophagy vesicles loaded with membranes.
51
Role of salmonella induced filaments?
Formation of filaments probably causes intracellular survival and replication of bacteria but not fully understood.
Possible role for egress.
52
Bacteria using the zipper mechanism.
Listeria, Yersinia.
53
Listeria - general bacterial invasion mechanisms
Actin rearrangements.
Microtubule dependent.
Intermediate filaments and septins contribute to invasion efficiency.
54
Bacteria using intermediate filaments and septins
E. Coli, Salmonella, Listeria, Shigella.
55
Listeria binding proteins
Internalins InlA and InlB anchored to membrane via LPXTG or GW motifs. Leucine rich repeats critical for function. Determine cell tropism and host range.
56
InlA - binding.
Binds E-Cadherin, species specific. Has leucine rich curve which grips around it.
Listeria.
57
E-Cadherin clustering (bound by InlA)
Zipper, Listeria.
| Binds catenins on cytoplasmic side. Interact with actin. Arp2/3 activated.
58
InlB - binding
Binds MET via LRR repeats which curve and grip. Listeria.
59
MET clustering due to InlB binding.
Mimics hepatocyte growth factor, but downstream recruits ABI and WAVE, and dynamin and cortactin.
60
Escaping the vacuole: Listeria.
Uses LLO and PLCs
61
LLO
Secreted by Sec. Thiol activated, reduced by GILT, optimally active at pH 5.5 Cholesterol dependent pore-forming toxin.
62
Action of LLO
Forms pore, interferes with iron gradients so no maturation and fusion of endosome. PLCs actually degrade vacuole.
63
Intracellular motility: Listeria
Surface protein ActA is a robust regulator of actin dep motility.
64
ActA structure.
```
VCA domain (mimics N-WASP) so recruits Arp2/3.
Polyproline repeats bind VASP (elongation and directionality). VASP cooperates with Arp2/3 - elongates F actin.
Does not have GBD or PRD domains so no sequestration.
Listeria
```
65
Listeria: actin in motility
Actin stays stationary, bacteria moves away.
66
Listeria: intracellular spread.
InlC, LLO, PlcB
67
Listeria: intracellular spread: InlC
Relaxes cortical tension by inhibiting host Tuba-WASP interactions (which provide the link between the membrane and the supporting cytoskeleton).
68
Listeria: intracellular spread: LLO
Lysis of 2nd vacuole.
69
Listeria: intracellular spread: PlcB
Closes protrusion.
70
Listeria invades which cells.
Transcytosis across M cells then into macrophages.
| Also invades epithelial cells by zipper mechanism.
71
Zipper mechanism.
Contact and adherence, phagocytic cup formation and phagocytic cup closure and retraction.
72
Cells taken up by phagocytosis
Legionella, Mycobacterium, Salmonella, Coxiella.
73
Trigger mechanism
repression of secretion, interaction and secretion, formation of macropinocytic pocket, actin depolymerisation and closing of pocket.
74
Cells taken up by phagocytosis: legionella
Legionella; a parasite of amoebae and macrophages which phagocytose, so does not drive uptake itself.
75
Cells taken up by phagocytosis: mycobacterium
Complement receptors and complement opsonisation are main routes of uptake. But specific receptor unimportant.
76
Phagocytosis: salmonella
Also taken up by trigger mechanism. Requires induction of membrane ruffling requiring WAVE.
77
Phagocytosis: coxiella
Binds αvβ3 which is normally used in phagocytosis of apoptotic cells so does not induce inflammation.
78
Listeria - regulation of virulence genes
Temperature change to 37 degrees --> conformational change in mRNA of PrfA --> can be translated --> makes PrfA --> activates small chromosomal pathogenicity island.
79
Actin polymerisation cascade - spontaneous.
G actin nucleates --> unstable actin nucleus --> elongated to F actin
80
Actin polymerisation cascade - spontaneous. G actin nucleates --> unstable actin nucleus.
Inhibited by profilin
81
Actin polymerisation cascade - spontaneous. Unstable actin nucleus --> elongated to F actin.
Increased by profilin/ATP-actin. Elongation inhibited by capping protein CapZ.
82
Actin polymerisation cascade - facilitated.
Attachment of Arp2/3 to a mother filament leads to branching. Profilin/ATP-actin used in elongation, with formin as capping protein.
83
Orientation of actin filaments in comet tails.
Barbed ends towards bacteria. Propulsive force provided by polymerisation.
84
ActA
Critical to virulence in the mouse model. Sufficient for comet formation. Activates Arp2/3.
85
Actin turnover in comet tails
Cofilin, coronin and capping proteins are important. Acceleration of this maintains actin monomer pool.
86
Actin comet tails formation overview.
Arp2/3 nucleates, VASP promotes speed and directionality, favours parallel filaments. Actinin stabilises. CapZ prevent nonproductive growth.
87
Autophagy pathway
Targets cytosolic proteins and organelles to lysosomes, a key innate immune response against intracellular bacteria.
Phagophore --> autophagosome --> lysosome.
88
Listeria and autophagy
LLO triggers by damaging vacuoles. ActA protects.
89
Rho GTPases
Master regulators of the actin cytoskeleton. Recruit/activate N-WASP and WAVE.
90
GEF
Guanine nucleotide exchange factor.
91
GAP
GTPase activating protein.
92
GDI
GTPase disassociation inhibitor.
93
WAVE
Have VCA domain for Arp2/3 activation.
94
Bacterial manipulation of Rho GTPases
Toxins tend to covalently modify, secreted effectors tend to mimic.
95
Avoiding autophagy
Actin helps evade autophagy (motility or actin shel).
| Phospholipases may degrade autophagosome.
96
Yersinia cell entry
Zipper mechanism into epithelial cells from basolateral side via invasins.
97
Invasins (Yersinia) - binding
Bind B integrins (usually mediate cell adhesion). Results in Rac1 remodelling and FAK recruitment. Src involved.
98
Key Rho GTPases
RhoA - stimulates focal adhesion and stress fibres
Rac1 - induces lamellipodia and ruffling.
Cdc42 - produces filopodia.
99
Invasins (Yersinia) - structure
Autotransport, not cleaved so anchored. D1, 2, 3 homo-oligomerise, D4, 5 bind integrins. Functionally mimics fibronectin (convergent evolution).
100
Yersinia resisting macrophage uptake
Uses YOPs.
101
Yersinia location
Inside epithelial cells, or in extracellular abscesses in Peyer's patches.
102
Inv locus Yersinia
Sufficient to convert E. Coli into bacteria which can penetrate cells. Codes for invasins
, critical for focal adhesion.
103
Yersinia: importance of clustering in integrin binding.
Without clustering of integrins, no signalling occurs.
104
Salmonella typhimuriusm functions of effectors in uptake
Interact with actin
Activate Rho GTPases by acting as GEFs
Activate Rho GTPases via inositol phosphate activity.
105
Salmonella typhimurium functions of effectors in uptake: interaction with actin
SipC nucleates and bundles
SipA is a molecular staple preventing ADF mediated dissassembly.
SipA potentiates SipC.
106
Salmonella typhimurium functions of effectors in uptake: activate Rho GTPases by acting as GEFs.
SopE activates Rac1, but SptP deactivates to restore actin cytoskeleton after invasion.
107
Salmonella typhimurium functions of effectors in uptake: activating Rho GTPases via inositol phosphate activity.
SopB makes PIP3 --> membrane ruffling. Binds ARNO for Arf1 activation. Arf1 + Rac1 recruit WAVE and Arp2/3.
108
Survival in vacuole: Salmonella induced filaments
Lysosomal membrane tubules induced by salmonella.
109
Survival in vacuole: Salmonella induced filaments formation
SifA --> SKIP (a linker protein to kinesin) --> would go to peripheral distribution of lysosomes in cells. PipB2 also involved.
110
Survival in vacuole: movement of SCVs to juxtanuclear region.
Near Golgi stacks.
Rab7 --> RILP --> dynactin --> dynein --> moves towards nucleus.
SseF and SSeG also involved.
111
Types of filament induced by salmonella
SNX tubules (sorting nexin), SCAMP3 tubules and LAMP negative tubules.
112
Salmonella - inducing cell death.
SlrP interacts with redox protein thioredoxin to cause apoptosis. SipB activates caspase 1 to cause macrophage death.
113
Salmonella: inhibition of immune response
NFkB pathway and mRNA
114
Salmonella: inhibition of immune response: NFkB pathway
Ubiquitin ligases IpaH and SspH1 are E3 ubiquitin ligases. Affects NFkB pathway and hence IL-8 production.
115
Salmonella: inhibition of immune response: mRNA
SpvC irreversibly removes phosphates reducing cytokine mRNA
116
Role of SPI-1 in salmonella uptake and cell infection.
Transcytosis across M cells.
Macrophage apoptosis and release of bacteria.
Uptake into cells.
117
Role of SPI-2 in salmonella uptake and cell infection.
Growth inside macrophages.
118
Salmonella divergence from E coli.
Acquisition of factors for intestinal colonisation - SPI-1
Acquisition of ability to cause systemic disease - SPI-2
Acquisition of ability to infect warm-blooded hosts.
119
Salmonella regulation of virulence genes.
Mg++/Ca++ high in gut lumen.
PhoPQ inactive in high salt conditions --> transcriptional activators like HilA --> SPI1 active.
PhoPQ active --> SPI-1 repressed, SPI-2 activated.
120
Salmonella effector translocation system
T3SS
121
SopB and SopE interactions in Salmonella
SopB generates PIP3, eventually recruits Arf1. SopE activates Rac1. Together they recruit WAVE.
122
Understanding salmonella infection
In mouse: bacteria invade, escape and infect many more cells.
In cultured macrophages: invade and replicate intracellularly.
In humans: rarely escapes gut.
123
Salmonella intracellular survival.
SPI-1 effectors --> early SCV formation.
Rabs are key to SCV formation and maturation.
Luminal environment triggers SPI-2 expression.
SPI-2 effectors maintain the vacuole, induce filaments and possibly have a role in egress.
124
Positioning of SCV.
SseF and SseG maintain. Tether in a Golgi associated manner. Promote interactions with dynein.
125
Salmonella typhi and paratyphi
Causes typhoid fever, a systemic disease.
126
Non typhoidal salmonella
Salmonella enterica serovars typhimurium (mouse is natural host in which it causes typhoid).
127
Number of SPIs
21, but 1 and 2 are the most studied
128
SPI-1 effectors --> early SCV formation.
Consider for entry
| SopB recruits Rab5.
129
Salmonella: avoiding delivery of acid hydrolases
Normally: cation-independent mannose-6-phosphate receptor delivers lysosomal hydrolases from TGN to early endosomes.
SNX1 retrieves these vesicles back to the TGN.
SNX1 binds PI3P produced by SopB, so is localised to near the SCV to protect it.
130
Sensing the luminal environment to express SPI-2 effectors.
SsrAB senses acidic environment and limitation of Pi. SsrB is the RR.
Causes transcription of T3SS and effectors.
131
SCV maturation to intermediate SCV
Rab5 replaced by Rab7 (migration to perinuclear region).
| SCV fuses with endosomes containing LAMP1 and vATPase.
132
SPI-2 encodes
A type III secretion system.
A two component system.
Effector proteins.
133
Interfering with NADPH oxidase - A. phagocytophilum
A. phagocytophilum interferes with assembly of NADPH oxidase subunits in inclusion membrane. and blocks activation of NADPH with phorbol myristic acetate.
134
Interfering with NADPH oxidase - Listeria
Listeria ribosylate Rab5 to inactive to prevent NADPH oxidase mediated killing before escaping vacuole.
135
Interfering with NADPH oxidase - Salmonella
Avoid recruitment.
136
SifA
Required for vacuole integrity. Anchored to SCV membrane.
SifA --> recruits SKIP --> reroutes M6PR, hydrolases secreted into extracellular medium instead. Rab9 retrieves M6PR from the PM.
137
Salmonella induced filament formation
PipB2 recruits kinesin.
SifA recruits SKIP, which activates kinesin.
Kinesin moves away from nucleus.
Generates Sifs, since SCV anchored by SseF/SseG.
138
SCV movement to perinuclear region.
Rab7 binding RILP and then dynein/dynactin motor complex, salmonella containing vacuole moves towards nucleus.
139
S. typhimurium broad host specificity
GtgE cleaves Rab32 which is necessary for lysosomal mediated death of S. typhi.
140
Cytolethal typhoid toxin exocytosis
Salmonella.
| Dependent on Rab27l
141
Salmonella T3SS
Similar to flagella.
142
Bacteria taken up by trigger mechanism
Salmonella, Shigella.
143
Shigella invasion site
Transcytoses M cells.
Taken up by macrophages, induce apoptosis.
Invades epithelial cells from the basolateral side.
144
Shigella general
Causes bacillary dysentry.
| Shigella dysenteriae, Shigella flexneri, Shigella sonnei, Shigella boydii.
145
Shigella regulation of invasive phenotype
The virulence plasmid is activated by VirF, a transcriptional regulator activated by physiological temperature. This causes transcription of VirF and VirB, which are also regulated by EnvZ-OmpR, CpxA-CpxR
146
Shigella effectors
IpgD (like SopB), IpaA (binds vinculin), IpgB1 activates Rac1.
IpaC is part of translocon, but indirectly activates Rac1 and Cdc42.
147
Escaping the vacuole: Shigella
Unknown mechanism. IpgD recruits Rab11. Unknown mechanism involves IpaB and IpaH. Possibly destabilising vacuole membrane.
148
motility: Shigella
IcsA for actin, VirA to sever microtubules.
149
IcsA structure and function.
Shigella. Identified in transposon mutagenesis.
| Autotransported by Ctd domain. Ntd has glycine rich repeats. Binds N-WASP, activates Arp2/3.
150
VirA: function.
Microtubule network hinders shigella motility. VirA is key to severance, controversy as to how - Yoshida suggested cysteine protease activity.
151
Actin motility with branched actin
Listeria and Shigella.
| Need ADF/cofilin, capZ and profilin.
152
Shigella: inducing cell death
IpaB activates caspase 1 causing macrophage death.
153
Shigella: inhibition of immune response: avoiding autophagy.
Actin based motility, actin shield and IcsB shield (competitively inhibits binding of autophagy related genes).
154
Shigella: intracellular spread.
Poorly characterised. Cell-cell junctions are subverted.
155
Mechanism of actin tails in Shigella
IcsA binds N-WASP. This binds Arp2/3 initially, and then feeds actin monomers onto the barbed end, propelling the bacterium away.
156
Role of actinin
cross-links actin.
157
Rickettsia motility
Doesn't use Arp2/3. Sca2 mimics formin to to generate unbranched acting polymers.
158
Determinants of vesicular transport
Membrane lipid composition
Membrane associated regulatory proteins
Lumenal environment.
159
Cellular compartment definition
Lipid phosphoinositides
| Rabs.
160
Ways to deal with lysosomal pathway
1) Uncouple early from pathway (Chlamydia, Legionella)
2) Escape vacuole (Listeria, Shigella)
3) Prevent progression to lysosome (mycobacterium)
4) Survive progression to lysosome (Coxiella)
161
LCV morphology
rER like. SldC promotes LCV-ER fusion.
Host proteins Sar1, ARF1 and Rab1 to recruit ER derived vesicles.
Recruit mitochondria.
162
Legionella secretion system
T4SS, dot-icm.
163
Number of legionella effector proteins
More than 300. Many interact with RhoGTPases or otherwise alter LCV morphology. Others provide nutrients. Examples: RalF, SldC, AnkB.
164
T4SS
Core complex spans both inner and outer membrane.
Self-assembling.
Has cytoplasmic inner membrane subcomplex with 3 ATPases. Membrane anchors link to the core complex.
165
Which bacteria use T4SSs?
H. Pylori, Brucella suis, Legionella pneumophila.
166
RalF
Sequence homology to Arf1 GEF. Arf is important in Golgi-ER retrograde transport and formation of secretory vesicles. Legionella.
167
AnkB
Recruits proteosome so that high levels of amino acids are generated by the LCV to provide nutrients. Legionella.
168
Legionella uptake
Phagocytosis.
169
Rab 1 control by Legionella.
SidM releases Rab1 from RabGDI. Recruited to LCVs. SidM converts to GTP bound form. Locks in constitutively active form by ampylation.
SidD deampylates later in infection, enabling deactivation by LepB.
170
Mycobacterial phagosome maturation block.
LAM: ManLAM blocks Ca++ rise, preventing PI3P synthesis.
PI3P is dephosphorylated due to SapM.
Trehalose dimycolate.
Rab7 is converted to its inactive GDP bound form.
171
EEA1
Tethering molecule essetial for fusion of early and late endosomes.
172
Mycobacterium: inhibition of immune response
Binding of TLR2 leads to potent pro-inflammatory cascade, and inhibits IFNy induction and induction of antigen presenting genes.
173
Mycobacterial cell wall
Lower segment
| Upper segment includes LAM and PIM
174
PIM stands for
Phosphatidylinositol mannosides.
175
Granuloma progression
Shed Mtb cell wall components. Exocytosed. Induce macrophage differentiation to foam cells. Undergo necrosis.
176
Mycobacterium secretion system
five ESX systems (T7SS)
177
Mycobacterial phagosome
Highly dynamic. Contains some lysosomal markers. Accessible to early and recycling endosomes.
Indicators of trafficking arrest: retention of Rab5 . No EEA1, vATPase, Cathepsin D or Rab7.
178
Mycobacterial damage to phagosomal membrane.
ESAT-6 and CFP-10 contribute to damage. Depend on each other for stability, secreted by ESX system.
179
Mycobacterial acquisition of iron.
Early endosomes accessible due to Rab5 marker: acquires iron from these.
180
Bacterial developmental transition on cell entry: Coxiella.
Small cell variant to large cell variant. Acidification = trigger.
181
Coxiella burnetti avoidance of killing.
Uses T4SS like legionella, but not involved in avoiding lysosome as only expressed 8 hours post-infections.
Delays hydrolases.
182
Roles of Coxiella effector proteins.
Promotion of CCV integrity.
Transcriptional modification.
Preventing apoptosis and cyt c release.
Proteasome mediated degradation for nutrients.
183
Coxiella vacuolar expansion.
Induces autophagy --> giant vacuole via Cig2.
Requires recruitment of Rho GTPase and Rab1b – maintenance and acquisition of additional membranes. Expand from small to large coxiella containing vesicles.
184
Intracellular bacteria rapidly escaping cell cytoplasm.2
Shigella, Listeria
185
Intracellular bacteria remaining withing the membrane bound vesicle.
Salmonella, Legionella pneumophila, Brucella abortus or Chlamydia spp
186
Intracellular survival
Bacterial developmental transition.
Stay in the vacuole?
Manipulating the host cell
187
Manipulating the host cell
Bacteria containing compartment interacting with other compartments.
Altering host cell death
Inhibiting immune response.
188
Exiting the host cell
Host cell death.
Exocytosis.
Intracellular spread.
189
Inhibiting the immune response - mechanisms
Alter TLR binding
Alter NFkB
Alter cytokine mRNAs
Avoid autophagy.
190
Bacteria using the zipper mechanism.
Listeria, Yersinia.
191
Microorganisms and regulation of virulence
Listeria, PrfA.
Salmonella PhoPQ
Shigella VirF.
192
Host cytoskeleton
Intracellular matrix that supports both shape and function.
Actin polymerisation
Rho GTPases
PIPs.
193
Shigella disease
causes shigellosis in humans (and apes) = dysentery with imbalance of host regulation of inflammation due to bacterial —> one of the leading bacterial causes of diarrhoea worldwide with at least 100,000 deaths (mostly children in developing world
four serogroups: s. dysenteriae causes epidemics whereas s. flexneri and s. sonnei are endemic
faeco-oral transmission
invades colonic mucosa to cause destructive recto-colitis, fever, cramps and bloody stool
194
Listeria disease.
food borne
causes gastroenteritis
invasive infection = listeriosis —> infection of the CNS — meningitis and brain accesses etc (only happens in immunocompromised, neonates, elderly, pregnant women and healthy persons who have ingested very large inoculum)
195
Shigella virulence plasmid
has 220kb virulance plasmid that has mxi-spa locus that encodes T3SS and effector proteins Ipa-Ipg
VirF responds to pH, 37 degrees C, osmolarity and iron to induce VirB expression with in turn induces T3SS and effectors
also regulated by TCSs: osmotic stress (via EnvZ/OmpR) and pH (via CpxAR)
196
Shigella: IpaB and C
bind cholesterol with high affinity and insert into membranes as translocon —> disrupt membrane to allow effector entry
197
Shigella: IpgD
interacts with PIP2 to induces actin rearrangements
198
Shigella: VirA
induces Rac1/Cdc42 dependent actin polymerisation and membrane ruffles
199
Shigella: IpgB1 and B2
act as GEFs for RhoA and Rac respectively to promote remodelling
200
Shigella: IpaA
mediates localised depolymerisation of actin via vinculin —> required to close the phagocytic cup
201
SopB and SopE interactions in Salmonella
SopB generates PIP3, eventually recruits Arf1. SopE activates Rac1. Together they recruit WAVE.
