Context-dependent siderophore exploitability shapes microbial community structure.

Siderophores are classically viewed as shared iron-scavenging public goods, yet their ecological roles in multispecies communities remain incompletely understood. Here, we establish a synthetic microbial community to dissect how different siderophores, their uptake compatibility and spatial structure shape iron competition. Using Corynebacterium glutamicum as a model, we show that this siderophore non-producer accesses diverse xenosiderophores, including enterobactin secreted by Escherichia coli. However, exploitation was constrained and co-cultures converged to stable compositions. Dose-response experiments combined with mathematical modelling indicated that the producer retains more effective access to enterobactin than the exploiter. The presence of Pseudomonas putida altered this interaction, as it exploited enterobactin while producing pyoverdine, a siderophore inaccessible to the other community members that restricted their iron access. Across different cultivation scales, community dynamics was strongly influenced by spatial organization and initial composition. These findings identify siderophores as context-dependent iron-allocation agents that can promote microbial coexistence or exclusion.