2-Bacterial Energy Transport and Scavenging Flashcards
What are ‘planktonic’ bacteria?
‘Free-flowing’ bacteria
In suspension
Not adherent/sessile (not in a biofilm)
What is a biofilm?
What functions does it have?
Biofilm = Structural community of bacteria cells enclosed in a self-produced polymeric matrix and adherent to a surface (Costerton & Co 1999)
It protects colony from dangers like bacteria
What is the process of biofilm formation?
1) Attachment - planktonic bacteria attach to surface
2) Micro-colony - bacteria dived and produce extracellular polymers
3) Mature Biofilm - when cells produce enough to form a polymeric matrix
4) Dispersal - nutrients run out or conditions change and cells revert to planktonic bacteria
Give 4 examples of processes that are monitored by bacteria
Self-monitoring - concentration of molecules within itself, e.g. Cyclic-di-GMP: high concentration=biofilm formation, low concentration = planktonic
Monitoring others/Intelligence gathering- quorum sensing, AHL’s
Motility- moving to better environment
Regulation of cellular processes - cell growth etc.
Give 5 examples of processes that a bacterial cell needs to carry out (and gain energy for)
1) Manufacturing - build cell components
2) Transport - import & export material
3) Surveillance - detect toxins / useful substances
4) Waste management - efflux systems
5) Energy Production - respiration, fermentation
What are the four stages of bacterial growth in batch culture?
1) Lag - growth is slow, bacteria adjust (change processes & gene expression) to suit new environment
2) Log- Increased production of cell components, cells rapidly divide
3) Stationary - toxins accumulate & nutrients run out, reduction in metabolic components and increase in components to deal with stress, no cell growth
4) Death- In culture, bacteria cannot move to find better environment, and bacteria die
What protein do E.coli use to produce ATP?
F-ATP synthase
- Membrane bound
- Has a rotating head
Describe how ATP is synthesised by this protein?
Protons from the periplasm pass through the F0 rotary motor
This causes the complex to rotate
Rotation causes ADP and Pi to be forced close enough to bond
Thus rotary motion is converted to chemical energy
What else are these proton-powered motors used for in some bacteria?
To run flagella-based motility systems
Name 5 types of cell transport
Facilitated Diffusion
Ion-coupled transport
Periplasmic-binding-protein (PBP) dependent ATP-drive
ATP-driven
Phosphoenolpyruvate (PTS), carbohydrate transfer system
Is facilitated diffusion passive or active?
Passive
What is a uniport system? Give one example.
Passive facilitated diffusion
Only one molecule is moving, via a membrane embedded protein (the facilitator)
Least common method of transmembrane transport
e.g. E.coli glycerol uniporter
What control do bacteria have over this uniport system diffusion?
None.
It is passive diffusion, no energy is used.
Diffuse can occur in both directions
Diffusion cannot go against the concentration gradient -> diffuses until equilibrium is reached.
What are symport-ion coupled systems?
Give and example
Ion and substrate pass in the SAME direction, through a symport protein.
Substrate requires an ion partner to pass through
E.g. Lac Permease
What is an antiport system?
Substrate and ion move in OPPOSITE directions.
Substrate requires a counter ion
Describe how a chemiosmotic circuit can be set up by ATP-ase, a symporter and an antiporter.
ATPase creates a proton gradient by pumping protons across the membrane
Symporter uses available ions (e.g. Na+) to transport substrate INTO the cell.
Antiporter uses the protons to pump the accumulated ions OUT of the cell.
What carbon source is preferred by bacteria and why?
Glucose
It is the easiest to metabolise and generates the most energy
Give an example of a scavenging system turned on when glucose is not available.
The lac operon for the uptake and metabolism of lactose. Three genes, ensures uptake and breakdown are regulated together.
What are the three parts of the lacZYA operon found in E.coli?
What are their functions?
LacZ protein gene = Beta-galastosidase (Lactase!), cleavage of lactose disaccharide into glucose + galactose
LacY permease gene = Beta- galactoside permease, symport transporter, uptake of lactose, membrane- embedded protein
LacA gene = Beta-galactoside transacetylase, catalyses the acetylation of galactosides, lactosides, glucosides…function still unknown!
What two regions of the E.coli genome are responsible for transport and metabolism of lactose in the cell?
LacI repressor AND Lac operon
What does the lac L repressor do?
It regulates operon activity upstream of the promotor
Describe the lac Y permease protein.
Membrane embedded protein
Symport transporter (proton and lactose INTO cell)
Twelve transmembrane regions, 80% alpha helical
Is there negative or positive transcriptional control on the lac operon?
Negative transcriptional control.
The repressor protein bound to the DNA inhibits initiation of transcription when there is no lactose present.
What is an operon?
Genes sequences, promotor region AND operator/activator binding sites
