# How flagellar glycosylation of the phytopathogenic bacterium Pseudomonas amygdali pv. tabaci 6605 affects transport and deposition in saturated sandy porous media

## TL;DR

This study explores how flagellar glycosylation in a plant pathogen affects its movement and retention in sandy soil, offering insights into managing bacterial contamination in agricultural settings.

## Contribution

The study reveals how flagellar glycosylation influences bacterial transport and deposition in porous media, providing new insights into microbial behavior in subsurface environments.

## Key findings

- Glycosylated flagella increase bacterial mobility and reduce retention in sandy porous media.
- Flagellar hydrophobicity enhances bacterial adhesion and deposition onto sand grains.
- Flagellar glycosylation introduces hydrophilic glycans that counteract adhesion effects.

## Abstract

To mitigate bacterial contamination in underground farmland, a comprehensive understanding of the transport and adhesion mechanisms of phytopathogenic bacteria in porous media is crucial for safeguarding soil and groundwater. This study aims to elucidate the effects of Pseudomonas amygdali pv. tabaci 6605 flagella (wild type, ΔfliC strain) and their glycosylation (Δfgt1 and Δfgt2 strains) on bacterial transport and deposition in sandy porous media through a combination of experimental observations and numerical simulations. Flagella play a key role in bacterial transport and deposition dynamics through its surface properties. Their intrinsic hydrophobicity enhances bacterial adhesion and promotes deposition onto sandy grains while simultaneously limiting transport through the porous medium. However, glycosylation of flagellin introduces hydrophilic glycans, which counteract this effect by increasing the overall hydrophilicity of the bacterial surface. As a result, glycosylated flagella facilitate bacterial mobility and improve recovery in the effluent while reducing retention within the sand matrix. These findings highlight the critical influence of flagellar biochemical modifications on bacterial behavior in porous environments. They provide valuable insights for understanding and managing microbial contamination in subsurface systems.

This work, conducted using homogeneous laboratory sand, could be extended to other types of abiotic media found in natural environments, such as clay, heterogeneous sands, and soils. Our study highlights the impact of flagellar glycosylation on bacterial behavior, an essential factor for assessing the risk posed by phytopathogenic bacteria in agricultural settings and for developing effective soil bioremediation strategies. Moreover, this study provides valuable insights into the mechanisms governing bacterial transport and deposition at the macroscopic (column) scale under dynamic flow conditions. Investigating unsaturated flow conditions, which better approximate real field scenarios, may further our understanding of bacterial interactions at air–solid–water interfaces. Future research should explore bacterial movement across different spatial scales. In particular, pore-scale experiments can provide direct evidence of processes such as attachment and motility. This could significantly enhance our understanding of microbial dynamics in complex environments.