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Surface Motility. a) Swarming - flagella. b) Twitching – Type IV pili (Retractile motility). c) Gliding - ?. d) Spreading - passive. Harshey, Ann Rev. Microbiol. 2003. Swarming Motility 1. Flagella-driven group motility on a surface
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Surface Motility a) Swarming - flagella b) Twitching – Type IV pili (Retractile motility) c) Gliding - ? d) Spreading - passive Harshey, Ann Rev. Microbiol. 2003
Swarming Motility 1. Flagella-driven group motility on a surface 2. Cell-density dependent lag prior to initiation of movement Swarming Movies 3. Swarming colony surrounded by a wet film which facilitates movement 4. Swarmer cells are ‘differentiated’- longer and more flagella
Swarmer cells are longer and have more flagella Broth - Swimmer Plate - Swarmer
What are the signals? How are the signals transduced to elicit cell differentiation?
Flagellar dynamometer controls swarmer cell differentiation of V. parahaemolyticus McCarter et al. 1988 Cell 54: 345-351
H+ Na+ High viscosity Low viscosity H+-driven Lateral flagella Na+-driven Polar flagellum Na+-driven Polar flagellum Vibrio parahaemolyticus has two different types of flagella Laf Pof
Two flagellar systems Broth: Fla Na+ ions Agar: Laf H+ ions
Agar Viscosity PVP Broth PVP Antibody agglutination Broth Induction of laf::lux in:
H+ Na+ High viscosity Low viscosity H+-driven Lateral flagella Na+-driven Polar flagellum Na+-driven Polar flagellum Vibrio parahaemolyticus has two different types of flagella Ab that tether Pof OR Slow motor rotation Laf Pof What if you destabilize the filament?
EM of mutants with flagellin gene defects DFlaAB FlaC
H+ Na+ High viscosity Low viscosity H+-driven Lateral flagella Na+-driven Polar flagellum Na+-driven Polar flagellum Vibrio parahaemolyticus has two different types of flagella Ab that tether Pof Mot mutations Che mutations Laf Pof
Effect of fla, che and mot mutations on laf::lux expression 1- Fla-; 2- Fla-; 3- Che-; 4- Mot-; 5- Fla- 6- Fla-; 7- Mot-; 8- WT; 9- Fla-; 10- Fla- 11- Fla-; 12- Che-; 13- Che-; 14- Che-; 15- WT WT
Interference with polar flagellar function signals Laf expression • 1. Increasing viscosity • 2. Antibodies • 3. FlaC mutations • 4. Mot mutations
Possible Mechanisms • Slow movement signals chemotaxis in reverse • High viscosity affects subunit assembly: • negative regulation of Laf assembly by FlaC • Flagellar torque imparts torsional force on cell body • All of these are physical signals!
The sodium-driven polar flagellar motor of marine Vibrio as the mechanosensor that regulates lateral flagellar gene expression Kawagishi et al., Mol. Microbiol. 20: 693-699, 1999
Hypothesis Rotation rate of OR External force applied against the polar flagellum controls laf expression
H+ Na+ High viscosity Low viscosity H+-driven Lateral flagella Na+-driven Polar flagellum Na+-driven Polar flagellum Vibrio parahaemolyticus has two different types of flagella Ab that tether Pof Mot mutations Na+ channel blockers Laf Pof
Effect of amiloride and its analogs on Growth laf expression
Effect of Phenamil Viscosity on Swimming speed● laf expression○
Conclusion A decrease in polar flagellar rotation rate, rather than the external force applied against the polar flagellum, can trigger swarmer cell differentiation
How is rotation rate sensed? Ion flux? But flux is coupled to rotation rate, so hard to separate. Also a marine bug like Vibrio has plenty of sodium around, so decrease in rotation should not affect total sodium flux in cell. Local ion concentration at the polar flagellum? Can this change the charge/conformation of an associated regulator of gene expression? Is assembly still an option?
H+ Na+ High viscosity Low viscosity H+-driven Lateral flagella Na+-driven Polar flagellum Na+-driven Polar flagellum Vibrio parahaemolyticus has two different types of flagella Ab that tether Pof Mot mutations Na+ channel blockers i.e. slow motor rotation Low Iron Laf Pof
Surface Motility a) Swarming - flagella b) Twitching – Type IV pili (Retractile motility) c) Gliding - ? d) Spreading - passive Gliding Movies Harshey, Ann Rev. Microbiol. 2003