Lecture 4: Quorum Sensing
- Created by: chandanee
- Created on: 03-01-19 12:40
View mindmap
- Quorum Sensing
- Sexual exchange Protecting your niche Combating host defences Population migrations
- Cell to cell communication: mechanism for GE, OG senses changes in the population density, when pop. reaches a critical size (quorate) behaviour changes.
- Needs a sensor kinase or response regulator by small diffusible signal mol
- Gram
- Gram -
- N-acylhomserine lactones (NAL), 2A4Q, DSF, C18-FAME
- E.g Pseudomonas aeru., resistant to Abs, opportunistic. Wound/catheter/eye infections/cystic fibrosis. Lots of protein secretion systems, VFs and control efflux pumps.
- lasR and lasL genes, las R binds to promoter and releases VFs such as elastase, exotoxin A, catalase, SOD. RhiR and RhiI also. RhiR controls more VF such as: pyocyanin, elastase, lectins, lipase. Also = pqs genes
- Mechanism: inability to express rhiAB and produce rhamnolipid surfactants.AAHL sensing controls motility. Biofilms: glue themselves together, form of attachment using pili, prevents dessication. Bilingual = antimicrobials, iron chelators, QS signal mols.
- Gram +
- y-Butyrolactones, cyclic peptides, CSP-1
- Autoinducing peptides (AIPs) lantibiotics, linear peptides, and cyclic peptides
- Hkp is phosphorylated = RRP > AIP HK RR = reg and target genes = virulence, competence, bacteriocins, sporulation
- Staphylococcus- controlled by Agr. Virulence determine by growth, colonisation factors and exotoxins. Agr neg = adhesins and Agr + = toxins.
- Hkp is phosphorylated = RRP > AIP HK RR = reg and target genes = virulence, competence, bacteriocins, sporulation
- Both: AI-2 and furanones
- Main difference between Gram + and - is that = NEG signal goes in and POS signal cascades
- Gram - = HK> RR Gram + = AI peptides go out of the cell, receptor binds, target DNA
- Versatility: cross signalling, persistence, Ab resistance, filamentation, biofilms, colonisation
- Gram -
- How and Why?
- Signal transduction > amp loop> signal synthesis > transducer = multiple gene expression
- Multiple GE: Ab production, symbiosis, virulence, swimming, conjugation, biofilm, growth inhibition
- Why communicate? To remain silent to then trigger virulence factors otherwise it can be eradicated by IS
- Signal transduction > amp loop> signal synthesis > transducer = multiple gene expression
- QS Inhibition
- QS Inhibiton - signal mol. biosynthesis and signal mol reception/decoding.
- Inhibition = by signal synthase inhibitors, receptor antagonists, enzymes, Abs, polymers
- PAN assay interference compounds = potency, high lipophilicity, metabolic instability, cytotoxicity.
Comments
No comments have yet been made