# Salmonella relies on siderophore exploitation at low pH

## TL;DR

Salmonella changes its iron acquisition strategy depending on the acidity of its environment, using more external iron-chelating compounds when conditions are acidic.

## Contribution

The study reveals a pH-dependent shift in Salmonella's reliance on endogenous versus exogenous siderophores for iron acquisition.

## Key findings

- Salmonella increasingly uses exogenous siderophores under acidic conditions.
- Low pH reduces the production of endogenous siderophores like enterobactin and salmochelin.
- The sigma factor RpoS influences iron homeostasis by modulating endogenous siderophore production at low pH.

## Abstract

Salmonella enterica, a prominent enteric pathogen, employs sophisticated iron acquisition mechanisms to overcome host-imposed iron limitation, notably through the production and uptake of siderophores—small, high-affinity iron-chelating compounds that scavenge iron from the host environment. In this study, we investigate how environmental pH influences Salmonella’s preference for its endogenous siderophores versus exogenous siderophores within the physiological range of the gastrointestinal tract. Through competition assays, gene expression analysis, and siderophore quantification, we demonstrate that Salmonella increasingly relies on exogenous siderophores under acidic conditions. This shift is attributed to reduced production of its endogenous siderophores, enterobactin and salmochelin. Deletion of the sigma factor RpoS enhances iron acquisition through increased endogenous siderophore production at low pH, suggesting a role in iron homeostasis regulation. Our findings reveal a pH-dependent difference in Salmonella’s iron acquisition strategy, highlighting the pathogen’s versatility in nutrient acquisition across varying gastrointestinal conditions. This research provides insights into Salmonella’s pathogenicity and may inform the development of targeted interventions for Salmonella infections.