Flashcards
Lecture 11 PMB
Cards in this deck (31)
- 1What does a capsule contain?Contains a polysaccaride and protein (hydrophilic polymer)
- 2What does a capsule do (in general)?Repels viruses & hydrophobic antimicrobial compounds, attaches to host, protects agains phagocytosis & desiccation, helps with biofilm formation
- 3What type of protein is the bacterial flagella?Is a helical polymer
- 4Where does the flagella attach to the cell?It is anchored to the cell membrane by the rotary motor
- 5What drives the rotary motor?It is driven by using a proton gradient across the cytoplasmic membrane
- 6Typical rates of cell movement300 Hz is max rate
1000 protons/revolution
cells can travel up to 60 cells/sec - 7Different rings within rotary motor and their locationMS ring anchor - cytoplasmic membrane
P ring anchor - peptidoglycan
L ring anchor - outermembrane - 8C ring proteinslocated on cytoplasmic face of membrane, can switch direction of motor and export flagellar proteins
- 9STATOR componentsMotA & MotB
MotB - PG layer; MotA - IM layer
protons pass through MotA which causes a conformational change in the rotor - 10ROTOR componentsFliG (in C ring, gets pushed), FliM and FliN determine which direction the rotor turns
- 11flagella biosynthesisthe base is built from inside to outside, with monomers added at the far end under the cap
early flagellar proteins: secreted into membrane by SecYEG pathway
mature flagellar proteins: secreted through axis of rod/hook/filament - 12How are flagella lost?By mechanical shearing
- 13How are genes for flagellar proteins transcribed?Transcribed through a hierarchy or transcriptional cascade
- 14What do the classes of the transcriptional cascade transcribe for?class I: master flagellar regulator
class II: MS, P, L rings, rod, hook, ALSO transcription factor that promote class III genes (σ28) alongside its repressor (FlgM aka anti-σ)
class III: flagellin and cap - 15When is FlgM activated?Activated while the basal body hook is still forming and then after the flagellum has fully formed
- 16Uses of Pili/fimbriaeUsed for :
1) twitching motility
2) bacterial conjugation (F pilus)
3) adherence to host tissues - 17Where are pili located, and what are they made of?Formed in the cell envelope and extend outside the cell; made of NON-helical filaments, typically covered with phage particles
- 18Type IV piliextend and retracts, aid in surface motility
- 19type IV pili proteinsexported in cytoplasmic membrane or periplasm using the Sec system
subunits are very hydrophobic --> stay attached to the IM until assembly at PilG.
The PilF ATPase = assembly
The PilT ATPase = retraction
assembled pilus travels through the OM in a large channel made of PilQ subunits - 20Pre-PilA and PilDpremature pre-PilA subunits get cut off, form mature unit PilD --> assembly occurs in PilG and units are pushed out
hydrophobic units degraded in periplasm - 21Pilus retraction in Pseudomonas aeruginosatype 4 pili
shows how extension of pilis pushes cell while retraction of pilis pulls, plus how pilis can adhere to surfaces - 22Type I/Pap pilipili that are not used for motility
can only attach and NOT retract
*used in uropathogenic E coli* - 23Type I pili proteinsSec pathway transfers subunits to periplasm, these bind to PapD chaperone that prevents subunit degredation and promotes assembly by PapC
PapH = termination unit = cap
PapA = main subunit
other Paps at tip bind to host epithelium - 24Type II secretion systemsexports protein substrates to extracellular space, related to Type IV pili
substrates --> periplasm : Sec system
periplasm --> EC space : ATP hydrolysis and pseudo (short) pilin polymerization/depolymerization - 25Type II secretion proteinsT2S makes the platform to assemble pili, Ctx extends to GM1 surface receptor
- 26Type III secretion systemsused to export substrates into the cytoplasm of a host cell, related to flagular hook-basal body (or needle) complex
*substrates are virulence proteins*
Sec system is NOT used for substrates, poke hole in cell membrane instead
energy from ATP hydrolysis - 27Yersinia sp. secretionUsing Type III secretion:
Yops affect actin cytoskeleton/focal adhesion --> inhibits phagocytosis
Other Yops inhibit MAP kinase signaling --> inhibits innate immune response.
*Toxins modify target proteins; sequester actin monomers; modulate GTPase activity + nucleotide exchange of target proteins* - 28Type VI secretion systemsused in cell-cell competition
T6SS built into innner membrane, when they contract --> puncture target membrane to deliver protein toxins
phage tail contracts --> puncture host cell and deliver genome - 29protection against protein toxinsTdi can cleave toxins, otherwise DNA may be degraded
individuals of same species have inhibitors of eachother's toxins, for other species they do not - 30P. aeruginosa vs V. chloraeVibrio attacks Pseudomonas --> P. starts signal cascade to build T6SS --> P. cell attacks V. with T6SS and lyses cell with toxins --> T6SS disassembled after attack
- 31main differences between secretion systems
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- Bacterial Appendages and Secretion Systems
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- Candice Young
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