Lecture 4 Flashcards
What are the 4 types of envelope modifications in prokaryotes?
1) Capsules and slime layers
2) S-layer
3) Flagella
4) Pili
What is a tightly attached “slime” called?
capsule
What is a loosely attached “slime” called?
slime layer
What is “slime” made of?
high-molecular-weight polysaccharide
Is the slime layer/capsule a target for vaccines? why?
yes, bc it’s the first bacterial structure encountered by immune system
What is capsular polysaccharides (CPS) usually composed of? charge?
typically negatively charged and can form 200 sugars long
Serotyping uses what to help distinguish isolates?
CPS
What allows insertion of the CPS into the membrane?
name? attached by what?
a phospholipid attached to the end of the CPS (hydrophobic)
called lyso-phosphatidylglycerol attached by Kdo linker
What are the 4 functions of the capsule?
1) acts as a sponge to retain water and nutrients
2) protection against desiccation
3) limits diffusion of harmful chemicals
4) aids in surface adherence and biofilm formation
How does the capsule protect against immune evasion?
protects against complement system
and via cationic antimicrobial peptide resistance (positively charged and bacteria is negatively charged)
How can you assay for capsule in the lab? (4)
1) Electron microscopy
2) calcofluor
3) biochemical isolation
4) capsule stain
Procedure of capsule stain?
1) coat with india ink
2) air dry (heat melts sugar in capsule)
3) saturate with crystal violet for 1 min
4) rinse with water and air dry, look under microscope
What is the role of the s-layer?
protection, structural support, permability barrier, mediate binding
Where is the s-layer found?
bacteria and archea
Where is the s-layer? for bacteria
anchored to the cell wall of Gram-positive bacteria and to the outer membrane of Gram-negative bacteria
Where is the s-layer? for archea
either cell wall or directly to the cell membrane
What is the s-layer made of? unique ability?
glycoproteins
can self assemble
What is the role of flagella?
locomotion
what is flagella at the end of a cell called?
polar
what is flagella all over the cell called?
perotrichous
more than one flagella?
flagellum
What is the structure of a flagellum?
1) long helical filament
2) connecting hook
3) basal body equipped with a rotor to turn the flagellum
Wha is the rotor power by?
proton motive force
What is the flagellum filament made of? structure?
rigid helical hollow structure made of flagellin that self-assembles
What is it important that the flagella is highly antigenic?
immune system can recognize
What is the structure of the hook?
short joint, curved
What is the basal body made of?
around 15 proteins that form a rod and anchors structure to cell membrane
What does CCW rotation move the bacteria?
foward
What does CW rotation move the bacteria?
tumble in place
how is a random walk produced?
alternating CCW and CW
What are endoflagella? ex?
flagella contained within periplasm, ex spriochetes
Why do few gram-positive bacteria have pili?
pili attach to the outer membrane which Gram+ bacteria do not have
Do pretty much all Gram- have pili or fimbriae?
yes
What are pili or fimbriae?
thinner and shorter flagella distributed in large numbers over the surface
Function of pili or fimbriae? (3)
1) attachement to surfaces
2) conjugation (transfer DNA/RNA)
3) motility
What is pili composed of?
oligomeric pilin proteins
what is the bottom/base of the pili called?
pilus
what is twitching motility?
pili are sticky and this is how they move,
extends and retraction due to polymerization and depolymerization
How do we assay motility in the lab?
1) dip sterile toothpick into bacterial suspension
2) poke swim agar with toothpick
3) incubate at desired temperature and measure zone of motility
what is the zone of motility?
diameter of colony
How do we know which part of the flagellum are crucial for motility?
mutants lose parts of flagellar apparatus and look for small zones of motility in assay motility
