Structural Macromolecules (Dr Alderwick): Part 2 Flashcards Preview

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Flashcards in Structural Macromolecules (Dr Alderwick): Part 2 Deck (22)
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1
Q

S-layer attachment in bacteria?

A
  • negative: LPS associated

- positive: PG and teichoic acids

2
Q

S-layer attachment in archaea?

A
  • negative: hydrophobic anchor

- positive: psedomurein

3
Q

Paracrystalline Surface Layer (S-layer_

- briefly describe what its found in..composition , arrangement etc

A
  • in many bacteria and all major lineages of archaea
  • composite of protein and glycopolymers
  • ordered symmetrical appearance (self arranging)
  • hexagonal, tetragonal and trimeric arrangement
4
Q

What is the function of S-layer in bacteria?

A
  • outermost layer - interaction with host
5
Q

What is the function of S-layer in archaea?

A
  • protection against osmotic pressure
  • protection against permeability layer and low pH, lysozyme and other lytic enzymes, adhesion esp glycosylated s-layers, protection against phagocytosis and other biological predators
6
Q

Why is the bacterial cell surface important?

- also + vs -?

A
  • site at which bacterial cell meets enviornment
  • host cell components
  • adhesion - colonisation
  • capsules and slime layers
  • gram +: fimbriae
  • gram -: fimbriae, pilus and type III - IV secretion systems
7
Q

Explain the bacterial cell surface structure fimbriae!

A
  • hair like proteinaceous appendages
  • 1- 20 uM in length and 20nm in diameter
  • gram neg bacteria Enterobacteriaceae and Neisseria gonorrhoeae
  • no motility function ****
  • antigenic and hemagglutinating properties - adherence to cells
8
Q

Explain the bacterial cell surface structure pilus

A
  • longer than fimbriae
  • serves to connect the bacteria to those of the same species, different species and host cells
  • made of an oligomer pilin
  • various types of this oligomer
  • Type IV pili = adhesion..surfaces, bacteria (colinsation and biofilm)
  • Sex pili: conjugation sex…transfer of plasmid DNA between species or across species…this transformation can lead to antibiotic resistance
9
Q

Difference between gram + and - pilus?

A
  • neg: pilin molecules attached via protein-protein interactions
  • pos: polymeriszed pilin appendage
  • *assembly is tightly regulated
10
Q

With the bacterial operon what are the two regions involved in pilus assembly. Explain them briefly

A
  • syntenic region: aka constant region –>these gene clusters are seen across many species and are very conserved (found in basal area)
  • variable regin: for the tip fibrium - these are highly variable and not conserved. Species specific thereby making them different from one another.
11
Q

Describe the bacterial pilus assembly pathway

A
  • Chaperone-usher pathway
  • SEC system
  • PapD= Chaperone
  • PapA, K, E, F and associated with PapD
12
Q

Explain bacterial conjugation

A
  • donor and recipient cell
  • line up
  • sex pili attachment occurs
  • DNA cleavage
  • linerisation of DNA
  • DNA transfer
  • DNA polymerase > re-circulation of DNA
13
Q

Explain briefly the mechanisms of bacterial motility! (archaea comparison)

A
  • flagella (primary role locomotion )
    • Bacterial: proteinaceous helical appendages
  • Archaeal: superficially similar to bacterial counterparts
  • *SHARE NO SEQUENCE HOMOLGY WITH BACTERIAL PROTEINS AKA THEY EVOLVED DIFFERENTLY
14
Q

Describe bacterial flagella !

A
  • long thin appendage: 15-20 nm in diameter ( largest app found)
  • attach in various cellular locations that are species specific
15
Q

What are the three cellular locations bacterial flagella can be in?

A
  1. Peritrichous -> developing all over the surface of the bacteria
  2. Polar -> one long one at one end
  3. Lophotrichous –> cluster of them at one end
16
Q

Flagella experiment with Rhodospirillum centenum revealed what about them?

A
  • when grown in liquid media it had a polar flagella
  • in solid media it had peritrichous flagella
    • arrangement is dependent on the enviornment and it can adapt locomotion abilities
17
Q

What drives flagellar rotation?

A
  • proton motive force
  • simple transport : driven by the energy in the proton motive force
  • *electrochemical gradient
18
Q

Describe the structure of the flagella?

A
  • L ring: located in the outer membrane
  • P ring:located in the peptidoglycan
  • MS ring: located in the cytoplasmic membrane
  • C Ring: located in the cytoplasm
  • 45 degree hook allows it to push through the enviornment!
19
Q

What is a Type III secretion ?

A
  • protein appendage found in only Gram negative bacteria
  • needle like structure
  • probe: sensory function to detect host organisms
  • secrete: inject effector proteins which signal the host cell to engulf the bacterium and tamper with the host cell cycle machinery
20
Q

Structure of Type III secretion complex?

A
  • similar to the flagella
  • evidence of evolution ??
    T3SS-> Flagella
    LPS
    OM
    Peptidogylcan
    IM
    Base= the above three
21
Q

Magnetotactic bacteria ?

  • discovered when?
  • how do they orient themselves?
  • move in response to?
  • major function is??
A
  • magnetic bacteria
  • discovered in 1975
  • orient themselves along the magnetic field lines of the earth
  • move in response to environments magnetic characteristics –> Magnetotaxis
  • *major function is unknown
22
Q

Magnetotactic bacteria :

  • contain what?
  • magnetosome forms via?
  • many species grow best where?
A
  • intracellular particles called magnetite- crystals of Fe3O
  • magnetosome form via a specialized invagination of the cytoplasmic membrane
  • magnetic dipole exerts this
  • many species grow best at low O2 concentrations
  • drives this aquatic cells downward towards low lying sediments