Biochemistry - Bacteria Communication Flashcards
Quorum Sensing
This allows bacteria to control gene expression in response to their population density through signalling molecules.
What does AI concentration increase in proportion to?
Cell density.
What happens when AI concentration increases?
Membrane receptor stimulation initating bacterial processes
What is the AI activation loop of GPB?
AIP secretion where at HC coinciding with HCD, interact with MR histidine kinases, initating autophos, phos cytoplasmic response regulators, activating QS regulon trans.
What is the AI activation loop of GNB?
Use smaller AI that freely diffuse acrros membrane, binding cytoplasmic receptors which act as TFs
Operon
A gene cluster transcribed together to produce a single mRNA encoding thus multiple proteins.
Why is QS important in S.Aureus?
In production of virulence factors in immunocompromised hosts for skin infections.
How is QS regulated in S.Aureus?
At the agr locus
agr locus
This in tandem with P2 promoter encodes QS components
What translates from P2 promoter in S.Aureus?
RNA11
What agr gene produces AIP?
AgrD
What is the synthesis process of AgrD AIP?
Synthesised as a 45 AA residue requiring metabolism to a 7-9 residue with following cyclization.
What is the transport regulator gene in s.aureus?
AgrA
What happens to AgrA
Phoshphorylated by membran bound histidine kinase s
Function of AgrA?
Induces Agr operons in neighbouring bcateria by stimulating P2 promter.
What is the hld gene in S.Aureus responsible for?
Coding delta hemolysin.
Function of RNAIII in S.Aureus?
Repression of toxin repressors and toxic virulence factor production.
What is the function of the S.Aureus QS system?
Biofilm formation inhibition, allowing Aureus to grow to HCD to stimulate QS.
What are the effects of cholera caused by?
Cholera Toxin
What are the two AI used in V.Cholera system?
s3-hydroxytridecan-4-one and AI-2
Why does V.Cholerae QS use two AI?
Allows both detection of other vibrio whilst also detecting total bacteria in the envrionment.
What is the pathway of kinases in Cholera?
Only kinase activtiy at LCD, converted to TFs at HCD
What do cholera TF at HCD do?
Activate gene expression of genes encoding QS sRNA.
Where do sRNA genes in cholera derive from?
Qrr genes
What is the function of the qrr gene products?
Regulation of base-pair binding to mRNAs econding the master regulator of the QS for cholerae.
What do sRNA function to do?
Bind master regulators hapR gene and aphA
What happens when sRNA bind hapR gene?
Disallow ribosomal binding and facilitate mRNA degradation
What happens when sRNA binds aphA?
mRNA binding induces secondary structure formation, revealing ribosomal binding sites, thus translation.
What is the master regulator compositiino at LCD?
High aphA levels and low hapR levels.
How is the expression ratio inversed at LCD?
AI binds intracellular kinases promoting downregulation of qrr expression.
What does AphA do at LCD?
Activate tcpPH gene.
What does LCD in cholera promote?
Biofilm formation due to less HapR
What does HapR do?
Repress genes constructing biofilm components and represses TFs promoting said genes
Why is biofilm formation important at LCD in cholera?
Promotes host attachment thus dispersal back into the envrionment.
