Biosynthesis of the Siderophore Desferrioxamine E in Rouxiella badensis SER3 and Its Antagonistic Activity Against Fusarium brachygibbosum

Iron is a limiting factor for plant and microbial growth because, in soil environments, it is predominantly present as oxyhydroxide minerals, rendering it unavailable to plants and microorganisms. Siderophores are chelating agents secreted to solubilize iron and facilitate its uptake. To understand the evolutionary and ecological dynamics of microbial communities, as well as the evolution of pathogens within hosts, it is essential to study the genes shared between microorganisms for environmental adaptation and survival. In this study, we conducted microbiological assays to evaluate the effect of the siderophore produced by Rouxiella badensis strain SER3 on the mycelial growth of fungal pathogens such as Fusarium brachygibbosum 4BF. Using spectrophotometric techniques and bioinformatics tools, we identified desferrioxamine E (nocardamine) in the culture supernatant, and the corresponding biosynthetic gene cluster in the SER3 genome was confirmed through antiSMASH analysis and synteny comparisons. Gene expression analysis by RT-PCR showed differential expression of biosynthetic precursors when strain SER3 was grown alone or in interaction with fungal pathogen. Finally, scanning electron microscopy revealed structural damage to F. brachygibbosum hyphae during co-culture with strain SER3. These results suggest that the production of desferrioxamine E may act as a biocontrol mechanism employed by R. badensis SER3 against F. brachygibbosum.