Siderophores can alter the population dynamics of fungal-bacterial communities by inhibiting specialized metabolism

Siderophores are microbial metabolites with a strong affinity for Fe(III) ions, in addition to other roles beyond iron acquisition. In this study, we propose that bacillibactin, a siderophore produced by the bacterium Bacillus subtilis , provides an advantage to its producer by inhibiting the specialized metabolism of antagonistic Penicillium fungi. Metabolome and transcriptome analyses indicate that iron deficiency caused by bacillibactin plays a critical role in downregulating the specialized metabolism of competing Penicillium species. Since many specialized metabolites of Penicillium spp. have antibacterial properties, we hypothesize that bacillibactin cross-protects other bacteria during fungal-bacterial community interactions. A tripartite coculture model demonstrated that bacillibactin production influences community dynamics by reducing the growth of specialized metabolite-producing Penicillium species, thereby facilitating the colonization of B. subtilis and other co-inhabiting bacterial species.