Prokaryotic Cells Flashcards
Name three intracellular membranes in photosynthetic bacteria that can be considered organelles.
- Intracytoplasmic membrane (proteobacteria)
- Thylakoid membrane compartments (cyanobacteria)
- Chlorosome compartments (Chlorobiaceae)
What do the three intracellular membranes in photosynthetic bacteria have in common?
They all maximise the efficiency of photosynthesis by
1) increasing the number photosynthetic protein complexes
2) maximizing the size of the light-exposed membrane surface
3) providing an idealized subcellular environment for photosynthesis
What are Planctomycetes?
True bacteria that contain a nuclear envelope
What percentage sequence identity can be found between MreB and eukaryotic actin?
15% sequence identity
What percentage sequence identity can be found between ParM and eukaryotic actin?
12% sequence identity
What is the role of
a) MreB?
b) ParM?
c) MamK?
a) MreB = cell shape
b) ParM = DNA partitioning
c) MamK = organelle assembly
Explain how ParM filaments are dynamic.
- Polymerisation of ATP-bound ParM occurs at both ends.
- ATP-hydrolysis occurs spontaneously.
- ParM is unstable when ParM-ADP is at an end.
Explain how ParM filaments segregate plasmids.
- ParR binds the centromeric DNA-sequence
- ParM polymerizes and binds to ParR
- Filament elongation separates the plasmids
What is the sequence identity between FtsZ and tubulin?
10-18%
What does FtsZ do?
Forms a ring at the cell cleavage site
If a cell has a mutant FtsZ, what is it defective in?
Cell separation
Give the four modes of motility.
- Swimming
- Swarming
- Gliding
- Twitching
When does swarming occur?
On surfaces
What is the swimming rate in bacteria?
25–160 micrometer per second
How many rotations per second in a flagellum?
100-300
What is the rate of surface-attached motility?
2-5 micrometers per second
How many pilli per cell?
100-1000
How long is a pillus on average?
And how wide?
1-2 micrometres long, 2-8 nanometers wide
How do Type 3 and Type 6 secretion systems work?
Inject proteins (15-30 proteins)
What do swimming or swarming depend on?
A rotating flagellum (that does not contain microtubules)
What is twitching motility based on?
Type 4 Pilli
What are type 4 pilli?
Protein assemblies that extend and retract to pull the cellover surfaces
How are cytosolic bacteria able to escape the phagocytic vesicle?
- By polymerising host actin at one end of the cell
- This “pushes” the bacterium through the cell but also spreads the bacterium from one host cell to the next
