Regulation of virulence factors Flashcards
What are promoter regions?
The 5’ untranslated region is mRNA that is directly upstream from the initiation codon
It has a critical role in recruitment of ribosomes to mRNA as well as many processes related to the mechanisms regulating translation
They contain conserved sequence that are recognised by RNA polymerase
How does RNA polymerase holoenzyme bind to promoters?
The holoenzyme is the core enzyme + sigma factor
The sigma factor is a bacterial transcription initiation factor that enables specific binding of RNA polymerase to gene promoters
What are transcriptional repressors and activators?
They are regulatory proteins; repressors shut down transcription, activators trigger transcription
They bind to motifs within DNA called operators; a single regulator can regulate several genes
What are virulence factors?
Factors required for host colonisation and damage; more than one virulence factor involved in pathogenesis; often co-ordinately regulated
Environmental cues signal the entry into host tissues and induce the expression of virulence factors:
Low Iron
Temperature
pH
Oxygen tension
Stress
What is an example of environment inducing toxin production?
Corynebacterium diphtheria is a Gram +ve, aerobic, rod shaped bacteria that is airborne and highly infectious. It is characterised by sore throat, cough, fever, enlarged lymp nodes.
A-B type toxins are induced in a low iron environment where the disease is more severe associated with toxin production encoded by the tox gene
Diphtheria toxin repressor (dtxR) is responsive to low iron levels - when iron is low it does not repress.
Has a successful vaccination programme
What are a couple of examples of similar dtxR proteins?
SloR in streptococcus mutans binds to Mn2+/Fe2+
MtsR in streptococus pyogenes binds to Mn2+/Fe2+
What is quorom sensing?
Bacterial quorom sensing is where bacteria communicate cell to cell by sending chemical signals, which can be referred to as AIs (auto-inducers), in order to regulate gene expression.
What was the first description of quorom sensing?
The LuxI/R system (transcription factors) in Vibrio fischeri - Gram -ve bacteria, a symbiont of marine animals.
Squids secrete a mucus gel to which V. fischeri binds and they migrate to organs.
Once the bacterial density reaches a certain threshold, the bacteria turn on the Lux system, producing bioluminescence
