The Gliding Motility of Myxobacteria

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The Gliding Motility of Myxobacteria

• Nan Chen and Yi-lin Wu
• Advisor Prof. Mark Alber
• Center for the Study of Biocomplexity, University
  of Notre Dame

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Proposed life cycle for Myxobacteria (Dale
Kaiser,2003 )
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The Gliding Motility

• Cell-end reversal both engine switch
• Reversal rate is regulated by C-signaling
• Plot of reversal rate versus signaling strength
  (FrzF activation rate) (Igoshin et al, 2004)

• Social motility puller
• Adventurous motility pusher
• AS 1.6micron/min A-S0.4 micron/min
  AS-0.6 micron/min (all maximum rates)

(Ref Dale Kaiser,2003)
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The mechanism of A-motility
RefHow Myxobacteria Glide, Charles Wolgemuth
Dale Kaiser et al, 2002
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• Hypothesis Slime secretion from the nozzle-like
  structures may provide the force needed to drive
  A-engine
• The force is due to the swelling property of
  polyelctrolyte gels, which have be found in
  slime. The calculated force is 50150 pN
  (calculations can be found in the handout paper)
• Not known how slime is introduced into the
  nozzle?

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A special case Flailing motion

• A myxobacteria cell is stuck at one end and the
  free end acts as A-engine
• Picture from Gliding Movements in Myxococcus
  xanthus, Alfred Spormann and Dale Kaiser, 1995

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Force and Flexibility of Flailing Myxobacteria
Biophysical Journal, Charles Wolgemuth,2005

• Model treating the cell as an elastic but
  inextensible filament of conserved length, L, and
  radius, a. The distance along the filament is
  parameterized by the arc length, s, and the shape
  of the filament is described by the vector r(s).

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Elastic energy
Elastic restorative force per length
Drag coefficients (proportionality constants for
movement perpendicular to or along the tangent
direction)
? is the tension is the filament, with ?(L)F,
the force produced by A-engine The following
equation is required by the non-stretching curve
dynamics
Ref. of the paper Nonlinear Dynamics of Stiff
Polymers, Phys. Rev. Lett., Goldstein and Langer,
1995
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Physical parameters
Nondimensionalizing (using FA/L2, fF/L)
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Results

• There exists a critical value (FL2/A37.5).
  Below this value, the filament remains straight
  above the value, it starts bending and flailing
  motion, which is consistent with experiment
  results.

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Results

• The relationship between the two parameters and
  flailing amplitudes as well as frequencies
• The model provide a new method to measure the
  A-engines propulsive force of gliding bacteria.

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Results

• The force F is found to be between 50-150 pN.
  This is consistent with the force predicted to be
  generated by slime extrusion. So the hypothesis
  that A-engine is driven by slime secretion is
  strengthened.

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My Suggestion

• The model might be useful in studying the bending
  and alignment when myxobacteria collide. (The
  S-end can be considered stuck to the other cell)