Heterogeneous bacterial swarms with mixed lengths.

Area of Science:

• Active matter physics
• Microbiology
• Biophysics

Background:

• Heterogeneous active matter systems display complex dynamics.
• Predicting mixed system properties from constituents is challenging.
• Bacterial swarms often develop heterogeneity naturally.

Purpose of the Study:

• Investigate the impact of cell aspect ratio heterogeneity on bacterial swarms.
• Determine if macroscopic phase segregation occurs in mixed swarms.
• Understand how heterogeneity affects swarming dynamics and speed.

Main Methods:

• Experimental study of mixed bacterial swarms.
• Computational simulations of swarming dynamics.
• Analysis of cell aspect ratios and their effect on collective motion.

Main Results:

• No macroscopic phase segregation observed in mixed swarms.
• Long cells act as nucleation sites for short, fast-moving cell aggregates.
• Local aggregation enhances swarming speeds, but high fractions of long cells create bottlenecks.

Conclusions:

• Spontaneous heterogeneity in bacterial populations offers a physical advantage for swarming.
• Cellular heterogeneity influences collective behavior and emergent properties.
• Understanding mixed systems is crucial for realistic bacterial swarm dynamics.