# Rectification of Twitching bacteria through narrow channels: A numerical simulations study

## TL;DR

This study uses numerical simulations to explore how narrow, structured channels can direct and optimize the movement of twitching bacteria, with potential applications in controlling biofilm formation.

## Contribution

It introduces a numerical analysis of bacterial twitching motility in corrugated channels using two models, revealing how surface geometry influences bacterial rectification and transport.

## Key findings

- Bacterial movement can be rectified in asymmetric channels.
- Transport efficiency depends on channel geometry and bacterial motility parameters.
- Optimal channel design enhances bacterial current for specific conditions.

## Abstract

Bacteria living on surfaces use different types of motility mechanisms to move on the surface in search of food or to form micro-colonies. Twitching is one such form of motility employed by bacteria such as N. gonorrhoeae, in which the polymeric extensions known as type IV pili mediate its movement. Pili extending from cell body adheres to the surface and pulls the bacteria by retraction. The bacterial movement is decided by the two-dimensional tug-of-war between the pili attached to the surface. Natural surfaces in which these micro-crawlers dwell are generally spatially inhomogeneous and have varying surface properties. Their motility is known to be affected by the topography of the surfaces. Therefore, it is possible to control bacterial movement by designing structured surfaces which can be potentially utilized for controlling biofilm architecture. In this paper, we numerically investigate the twitching motility in a two-dimensional corrugated channel. The bacterial movement is simulated by two different models: (a) a detailed tug-of-war model which extensively describe the twitching motility of bacteria assisted by pili and (b) a coarse-grained run-and-tumble model which depicts the motion of wide-ranging self-propelled particles. The simulation of bacterial motion through asymmetric corrugated channels using the above models show rectification. The bacterial transport depends on the geometric parameters of the channel and inherent system parameters such as persistence length and self-propelled velocity. In particular, the variation of the particle current with the geometric parameters of the micro-channels show that one can optimize the particle current for specific values of these parameters.