Structural Macromolecules (Dr Alderwick): Part 2 Flashcards Preview

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

S-layer attachment in bacteria?

- negative: LPS associated
- positive: PG and teichoic acids


S-layer attachment in archaea?

- negative: hydrophobic anchor
-positive: psedomurein


Paracrystalline Surface Layer (S-layer_
- briefly describe what its found in..composition , arrangement etc

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


What is the function of S-layer in bacteria?

- outermost layer - interaction with host


What is the function of S-layer in archaea?

- 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


Why is the bacterial cell surface important?
- also + vs -?

- 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


Explain the bacterial cell surface structure fimbriae!

- 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


Explain the bacterial cell surface structure pilus

- 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


Difference between gram + and - pilus?

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


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

- 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.


Describe the bacterial pilus assembly pathway

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


Explain bacterial conjugation

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


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

- flagella (primary role locomotion )
- Bacterial: proteinaceous helical appendages
- Archaeal: superficially similar to bacterial counterparts


Describe bacterial flagella !

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


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

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


Flagella experiment with Rhodospirillum centenum revealed what about them?

- 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


What drives flagellar rotation?

- proton motive force
- simple transport : driven by the energy in the proton motive force
**electrochemical gradient


Describe the structure of the flagella?

- 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!


What is a Type III secretion ?

- 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


Structure of Type III secretion complex?

- similar to the flagella
- evidence of evolution ??
T3SS-> Flagella
Base= the above three


Magnetotactic bacteria ?
- discovered when?
- how do they orient themselves?
- move in response to?
- major function is??

- 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


Magnetotactic bacteria :
-contain what?
- magnetosome forms via?
- many species grow best where?

- 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