Understanding how bacterial collectives organize on surfaces by tracking surfactant flow

Area of Science:

• Microbiology
• Biophysics
• Fluid Dynamics

Background:

• Swarming is a collective bacterial behavior enabling population expansion and evasion of stressors like antibiotics.
• The precise mechanisms organizing bacterial swarms, particularly in *Pseudomonas aeruginosa*, remain poorly understood.
• Existing models propose bacterial sensing and fluid mechanics as key drivers of swarming.

Purpose of the Study:

• To investigate the role of fluid mechanics in *Pseudomonas aeruginosa* swarming.
• To explore the relationship between tendril formation and surfactant flow during swarming.
• To provide new insights into the interplay of biological processes and fluid dynamics in bacterial collective behavior.

Main Methods:

• Review of existing models for bacterial swarming.
• Development and application of a novel imaging technique, Imaging of Reflected Illuminated Structures (IRIS).
• Tracking of tendril movement and surfactant flow in *P. aeruginosa* swarms.

Main Results:

• Tendrils and surfactants form distinct, interlinked layers within the swarm.
• These layers exhibit synchronized growth, expanding in lockstep.
• The synchronized growth suggests a significant impact of surfactant flow on tendril development.

Conclusions:

• Swarm organization in *Pseudomonas aeruginosa* is a complex interplay between biological factors and fluid mechanics.
• The findings challenge existing swarming models by highlighting the role of surfactant dynamics.
• Further research is needed to fully elucidate the mechanisms governing bacterial swarm structure and expansion.