Actin-mediated bacterial propulsion: comet profile, velocity pulsations

Area of Science:

• Biophysics
• Cellular Mechanics
• Microbiology

Background:

• Bacteria utilize actin networks for propulsion.
• Understanding bacterial motility in complex environments is crucial.
• Actin gel dynamics influence cellular movement.

Purpose of the Study:

• To model bacterial propulsion within actin gel networks.
• To elucidate the roles of gel elasticity and polymerization in motility.
• To determine conditions for motion onset and identify distinct velocity regimes.

Main Methods:

• Developed a model incorporating network elasticity, gel-bacterium interaction, and polymerization dynamics.
• Derived a formula for bacterial cruise velocity.
• Analyzed system behavior by varying growth rates and gel elasticity.

Main Results:

• Obtained an explicit formula for cruise velocity, separating elasticity and polymerization contributions.
• Observed that higher velocities correlate with lower concentration peaks and longer tails.
• Identified two steady-state regimes: constant velocity and pulsating velocity.
• Found that increased gel elasticity triggers the transition to pulsating velocity.

Conclusions:

• Bacterial propulsion is quantitatively explained by actin gel concentration dynamics.
• Gel elasticity and polymerization are key drivers of bacterial motility.
• The model predicts and explains observed phenomena like pulsating velocity regimes.