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Quorum Sensing

Quorum Sensing. Three Classes of autoinducer signaling molecules identified Oligopeptides or autoinducing peptides (AIPs) - 2. Acylated homoserine lactones (acyl-HSLs) – 3. Interconvertible furanone derivatives (AI-2) –. Quorum Sensing.

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Quorum Sensing

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  1. Quorum Sensing Three Classes of autoinducer signaling molecules identified Oligopeptides or autoinducing peptides (AIPs) - 2. Acylatedhomoserine lactones (acyl-HSLs) – 3. Interconvertiblefuranone derivatives (AI-2) –

  2. Quorum Sensing Examples of homoserinelactone signaling molecules

  3. 1. Bioluminescence • Most commonly seen in marine bacteria • Some can live as either symbiotes in light organs of fish or be free living • Some strictly free living • Also seen in a few bacteria • found in freshwater and soil

  4. Bioluminescence observed in this class in a previous year (2010)

  5. 1. Bioluminescence Mediated by an enzyme luciferase Light emitted continuously for a while Oxygen reacts with FMNH2 and an aldehyde (RCHO). Creates FMNH-OH* with an excited electron and a carboxylic acid (RCOOH) Light is emitted from FMNH-OH and water and FMN is formed Fig 18.33 White

  6. 1. Bioluminescence A. Luminescence in Vibriofisheri LuxI Acyl-HSL 3. LuxR Fig 18.36 White Similar to Fig 12.30 in BactPhy

  7. 1. Bioluminescence B. Luminescence in Vibrioharveyi Two autoinducers AI-1 – acyl-HSL type AI-2 – furanone compound made by LuxS Both activate LuxU and LuxO Fig 18.37 White

  8. 2. Biofilms Community of bacterial cells living within an extracellular matrix that is attached to a surfacebathed by water Now thought to be common growth state of bacteria in our environment

  9. 2. Biofilms Observed on rocks and surfaces in streams and oceans, in pipes in medical equipment (tubes) On surface of teeth (plaque), mouth, and intestines (mostly normal flora), and in lungs (pathogens)

  10. 2. Biofilms Form discrete structures Mushrooms or pillars Streamers (higher flow) Left (red): Lungs Right: rocks in stream Battin et al 2007 Nat Rev Micro 5:76

  11. 2. Biofilms a-c: hot springs d-e: streams f-i: lab flowcell a, d, g: low flow – mushrooms or mound b-c, e-f, h-i: high flow causes streamers Hall-Stoodley et al 2004 Nat Rev Micro 2:95

  12. 2. Biofilms Matrix material – extracellular polymeric substances (EPS) Made by bacterial cells of biofilm Composition varies between species and perhaps conditions Types of molecules found

  13. 2. Biofilms Often a community of different kinds of bacteria are found within the biofilm (dental plaque)

  14. 2. Biofilms Advantages Provides means by which bacteria can be attached to a surface (not washed away) Allows bacteria to stay close to a nutrient source Can contain different species that work together in a food web (Anaerobic food chain) Protection from chemicals (antibiotics)

  15. 2. Biofilms Stages in biofilm formation Thought to be example of bacterial multicellular development Initial Attachment – planktonic, swimming bacteria attach to a surface, may be type 1 pili mediated Irreversible attachment –form monolayer by type IV twitching motility Maturation part 1 – form microcolonies with mushrooms or pillars Maturation part 2 Dispersal – some become motile again

  16. 2. Biofilms Quorum sensing in Pseudomonas aeruginosa Two Lux like systems – las and rhl Each makes a different acyl-homoserinelactone Bacterial Stress Responses. Storz and Hengge-Aronis ed

  17. Assignment 10 • Read two papers on Biofilms for Friday and answer questions • Bring papers to class • Will work on New assignment #11 in class together during class

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