E. coli Biofilms Exam Flashcards
In what direction does the Petricous Flagella move in E. coli?
counter clockwise
Where do you find E. coli?
Mainly in the Guts of mammals but can be found everywhere
What information is there about Antigen 43?
- There are 50,000 copies per cell
- Autotransporter
- Encoded by the flu gene
- Important for biofilm formation
What are the O2 requirments of E. coli?
Faculatative anerobic
What surface proteins does E. coli have that are important for biofilm formation?
- Antigen 43
- Type 1 Fibriea
- Curli Fimbria
- Pili
- Flagella
What is some information about type 1 Fimbriae?
- Encoded on the fim switch gene
- 100-500 per cell
- adheres to the host mannose receptors
What is some information on curli fimbriae?
- Encoded on the csgBADEFG operon
- Binds to the host fibronectin
- Polar bond to the surface: part of the irreversible attachment
- Aggregation: cell surface aggregation good for nutrients
- Initial attachment
- Involved in cell-to-cell interactions
What is the F-Pilus? and general information
- type IV secretion system encoded by the tra locus
- coded on the conjugation plasmid
- Involved in initial attachment
- Horizontal gene transfer
- Conjugative plasmid: contains adhesion factors on mobile genetic elements
Information about the flagella?
when flagella concentrations are low the there is upregulation of C-di-GMP
If flagella gene knocked out biofilm formation reduces or doesn’t happen at all
What are important biofilm molecules involved in biofilm structure and EPS in E. coli?
- PNAG
- Cellulose
- Colanic acid
- c-di-GMP
What is the most common pollysacharide in the E. coli EPS?
PNAG
What is the structural polysaccharide in E. coli?
Cellulose
What is cellulose’s role in E. coli?
Structure
Works in tandem with curli fimbriae to create elasticity and morphology of the biofilm shape
Creates baskets with amyloid proteins: aids in aggregation of nutrients
What is colanic acid and how does it affect the biofilm?
negatively charged polymer
Creates the capsule of the E. coli
What is dispirsin and what does it do to the biofilm?
Prevents electrostatic interactions of the curli fimbraies
What are the Two, Two-component systems in E. coli?
RCS system
CPXRA
how does the RCS two-component system work?
Phosphorelay system: Which mediates biofilm formation
- RscC: Sensor kinase: Transfers a phosphate to RcsB via RscD: responds to the surface changes. Regulates the CPS operon which encodes for colanic acid.
- RscD: histidine-containing phospho-transmitter domain protein
- RcsB: Regulatory protein: activates the RCS system. Acts as an inhibitor in other systems
- RcsP: Outer membrane protein: Periplasm
- RcsA: positive regulator of wza-wca cluster genes
What are all the proteins that are in evolved in the Rcs operon?
RcsA, RcsB, RcsC, RcsD, RcsF
What does the CpxRA tw0-component system regulate and what does it respond to?
Upregulates pilus assembly, motility chemotaxis, and adherence
Senses changes on the surface adapt to the environment and upregulate adhesion molecules. type III secretion systems and cell-to-cell signalling
What is the CpxRA to-component system? and what can it lead to?
phosphorelay system: can lead to multidrug resistance
- cpxA: Sensor histidine kinase: It phosphorylates cpxR: has a Mg2++ cofactor. Activated by cell stress.
- cpxR: cytoplasmic regulator: once phosphorylated it acts a transcription factor and binds to the promoter
- cpxP: periplasmic protein which inhibits cpxA
What are the proteins involved in the cpxRA two-component system?
cpxA
cpxR
cpxP
What are the four general steps for quorum sensing?
- synthesis of signal molecules (autoinducers)
- excretion of signalling molecules
- activate receptors
- repression of gene expression
What are the two quorum sensing pathways in E. coli?
AI-2
AI-1 (AHL)
What is AI-2 enzyme in e. coli?
Luxs enzyme
What are the stages of AI-2 pathway in quorum sensing?
- AI-2 binds to e-coli receptor
- LsrACDB transporter brings the AI-2 in
- LrsK phosphorylates the AI-2
- The phosphorylated AI-2 prevents the LaskR from repressing the LSR gene.
- Lsr gene is expressed
- Lsf&Lsg heteroprotein degrade the AI-2
What are the proteins involved in the AI-2 pathway of quorum sensing?
AI-2
LsrK
LsrR
LsrF
LsrG
What is the gene that is activated by AI-2?
Lsr operon
Does E. coli make AI-1?
NO
What molecule inhibits the AI-1 pathway?
glucose
What are the steps of AI-1 in e. coli quorum sensing?
- AHL binds to the E. coli receptor
- AHL is transported into the cell
- AHL binds to SdiA
- SdiA upregulates YdiV
- YdiV upregulates the PAP2 operon: upregulating fimbria production and synthesising PAP X
- PAPX binds to and inhibits the flhD promoter, which then downregulates the flagella and fimbriae production increases.
- SdiA & YdiV activate the cya and crp genes. CYA produces cAMP and crp produces CAP
- cAMP binds to CAP: which in turn binds to the lsrR promoter upregulating the lsr gene.
What are the foure host receptors that E. coli commonly binds?
Mannose
Amyloid
Fibonectin
Collagen
