Lecture 11 PMB

Pregunta	Respuesta
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	Image: Screen Shot 2017 10 27 At 5.31.17 Pm (binary/octet-stream)

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