Created by Candice Young
almost 7 years ago
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Question | Answer |
What does a capsule contain? | Contains a polysaccaride and protein (hydrophilic polymer) |
What does a capsule do (in general)? | Repels viruses & hydrophobic antimicrobial compounds, attaches to host, protects agains phagocytosis & desiccation, helps with biofilm formation |
What type of protein is the bacterial flagella? | Is a helical polymer |
Where does the flagella attach to the cell? | It is anchored to the cell membrane by the rotary motor |
What drives the rotary motor? | It is driven by using a proton gradient across the cytoplasmic membrane |
Typical rates of cell movement | 300 Hz is max rate 1000 protons/revolution cells can travel up to 60 cells/sec |
Different rings within rotary motor and their location | MS ring anchor - cytoplasmic membrane P ring anchor - peptidoglycan L ring anchor - outermembrane |
C ring proteins | located on cytoplasmic face of membrane, can switch direction of motor and export flagellar proteins |
STATOR components | MotA & MotB MotB - PG layer; MotA - IM layer protons pass through MotA which causes a conformational change in the rotor |
ROTOR components | FliG (in C ring, gets pushed), FliM and FliN determine which direction the rotor turns |
flagella biosynthesis | the 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 |
How are flagella lost? | By mechanical shearing |
How are genes for flagellar proteins transcribed? | Transcribed through a hierarchy or transcriptional cascade |
What 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 |
When is FlgM activated? | Activated while the basal body hook is still forming and then after the flagellum has fully formed |
Uses of Pili/fimbriae | Used for : 1) twitching motility 2) bacterial conjugation (F pilus) 3) adherence to host tissues |
Where 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 |
Type IV pili | extend and retracts, aid in surface motility |
type IV pili proteins | exported 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 |
Pre-PilA and PilD | premature pre-PilA subunits get cut off, form mature unit PilD --> assembly occurs in PilG and units are pushed out hydrophobic units degraded in periplasm |
Pilus retraction in Pseudomonas aeruginosa | type 4 pili shows how extension of pilis pushes cell while retraction of pilis pulls, plus how pilis can adhere to surfaces |
Type I/Pap pili | pili that are not used for motility can only attach and NOT retract *used in uropathogenic E coli* |
Type I pili proteins | Sec 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 |
Type II secretion systems | exports 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 |
Type II secretion proteins | T2S makes the platform to assemble pili, Ctx extends to GM1 surface receptor |
Type III secretion systems | used 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 |
Yersinia sp. secretion | Using 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* |
Type VI secretion systems | used 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 |
protection against protein toxins | Tdi can cleave toxins, otherwise DNA may be degraded individuals of same species have inhibitors of eachother's toxins, for other species they do not |
P. aeruginosa vs V. chlorae | Vibrio attacks Pseudomonas --> P. starts signal cascade to build T6SS --> P. cell attacks V. with T6SS and lyses cell with toxins --> T6SS disassembled after attack |
main differences between secretion systems |
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