Surface Motility

1
Surface Motility
a) Swarming - flagella
b) Twitching Type IV pili (Retractile
motility)
c) Gliding - ?
d) Spreading - passive
Harshey, Ann Rev. Microbiol. 2003
2
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
3
Swarmer cells are longer and have more flagella
Broth - Swimmer
Plate - Swarmer
4
What are the
signals? How are the signals transduced to
elicit cell differentiation?
5
Flagellar dynamometer controls swarmer cell
differentiation of V. parahaemolyticus
McCarter et al. 1988 Cell
54 345-351
6
Vibrio parahaemolyticus has two different types
of flagella
Laf
Pof
7
Two flagellar systems
Broth Fla Na ions
Agar Laf H ions
8
Reporter system used in this work
9
Induction of laflux in
10
Vibrio parahaemolyticus has two different types
of flagella
Ab that tether Pof OR
Slow motor rotation
Laf
Pof
What if you destabilize the filament?
11
SDS-PAGE of purified flagella in various strains
12
EM of mutants with flagellin gene defects
DFlaAB
FlaC
13
Vibrio parahaemolyticus has two different types
of flagella
Ab that tether Pof Mot mutations Che mutations
Laf
Pof
14
Effect of fla, che and mot mutations on laflux
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
15

• Interference with polar flagellar function
  signals Laf expression
• 1. Increasing viscosity
• 2. Antibodies
• 3. FlaC mutations
• 4. Mot mutations

16

• 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!

17
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
18
Hypothesis Rotation rate of
OR External force applied
against the polar flagellum controls laf
expression
19
Vibrio parahaemolyticus has two different types
of flagella
Ab that tether Pof Mot mutations Na channel
blockers
Laf
Pof
20
Effect of amiloride and its analogs on
Growth
laf expression
21
Effect of Phenamil
Viscosity
on Swimming speed ? laf
expression ?
22
Relationship between swimming speed and laf
induction
23
Conclusion
A decrease in polar flagellar rotation rate,
rather than the external force applied against
the polar flagellum, can trigger swarmer cell
differentiation
24
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?
25
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
26
Surface Motility
a) Swarming - flagella
b) Twitching Type IV pili (Retractile
motility)
c) Gliding - ?
d) Spreading - passive
Gliding Movies
Harshey, Ann Rev. Microbiol. 2003