A dynamic preferred direction model for the self-organization dynamics of bacterial microfluidic pumping

Area of Science:

• Microbiology
• Biophysics
• Fluid Dynamics

Background:

• Flagellated bacteria like Serratia marcescens can form biofilms on surfaces.
• Collective flagellar motion in bacterial carpets can generate fluid flow.
• This phenomenon has potential applications in microfluidics.

Purpose of the Study:

• To develop a continuum model describing bacterial self-organization and fluid pumping.
• To quantify the relationship between bacterial collective motion and microfluidic channel width.
• To investigate the underlying mechanisms of self-coordination in bacterial carpets.

Main Methods:

• Developed a continuum model with two macroscopic variables.
• Introduced collective angular velocity of helical flagella as a source of activity.
• Analyzed the model to agree with experimental observations of pumping in microfluidic channels.

Main Results:

• The model successfully describes and quantifies the self-organization mechanism.
• A positive feedback loop between flagellar rotation and local flow was identified.
• The model shows agreement with experimentally observed channel width dependence of pumping.
• The biological active system operates near the self-organization threshold.

Conclusions:

• Bacterial collective motion and flagellar coordination are driven by a positive feedback loop.
• The developed model provides a quantitative framework for understanding this phenomenon.
• The findings suggest that bacterial active systems can operate close to self-organization criticality.