Intermittent turbulence in flowing bacterial suspensions

Area of Science:

• Microbiology
• Fluid Dynamics
• Biophysics

Background:

• Dense bacterial suspensions exhibit collective motion.
• This motion is analogous to high Reynolds number turbulence.
• The analogy has remained largely qualitative.

Purpose of the Study:

• Quantify velocity statistics in flowing bacterial suspensions.
• Investigate the link between bacterial collective dynamics and turbulence.
• Explore microfluidic models for the human gut microbiome.

Main Methods:

• Dense Bacillus subtilis suspensions were flowed through microchannels.
• A novel velocimetry technique was employed for quantification.
• Vortex identification and Lagrangian tracking were utilized.

Main Results:

• Observed robust intermittency in the suspension's average velocity profile.
• Flow profiles fluctuated between plug-like and parabolic.
• Transient vortices from bacterial motion reinforced the imposed flow.

Conclusions:

• Bacterial collective motion can induce turbulence-like intermittency.
• Transient vortices are key to this phenomenon.
• Microfluidics can model human microbiome environments.