# Enhanced propagation of motile bacteria on surfaces due to forward scattering

## TL;DR

This study reveals that micro-obstacles can enhance bacterial movement on surfaces through forward scattering, challenging the notion that obstacles only hinder motility, with implications for microbial ecology and biofilm formation.

## Contribution

It demonstrates that low obstacle densities can promote bacterial propagation via forward scattering, a novel insight into bacteria-surface interactions in complex environments.

## Key findings

- Optimal obstacle density enhances bacterial propagation.
- Forward scattering events increase motility.
- Microstructure influences bacterial surface movement non-monotonically.

## Abstract

How motile bacteria move near a surface is a problem of fundamental biophysical interest and is key to the emergence of several phenomena of biological, ecological and medical relevance, including biofilm formation. Solid boundaries can strongly influence a cell's propulsion mechanism, thus leading many flagellated bacteria to describe long circular trajectories stably entrapped by the surface. Experimental studies on near-surface bacterial motility have, however, neglected the fact that real environments have typical microstructures varying on the scale of the cells' motion. Here, we show that micro-obstacles influence the propagation of peritrichously flagellated bacteria on a flat surface in a non-monotonic way. Instead of hindering it, an optimal, relatively low obstacle density can significantly enhance cells' propagation on surfaces due to individual forward-scattering events. This finding provides insight on the emerging dynamics of chiral active matter in complex environments and inspires possible routes to control microbial ecology in natural habitats.