TY - CONF A1 - Schumacher, Julia T1 - Iron Acquisition in Black Fungi: Genomic Insights & Mitigation N2 - Iron is an essential micronutrient for all organisms, driving intense competition for its acquisition. This competition is particularly evident in parasitic interactions, where hosts actively restrict iron availability to inhibit the growth of fungal invaders (nutritional immunity). Saprobic fungi, on the other hand, acquire iron by digesting dead organic material and may protect their nutrient sources from competitors through efficient iron uptake, rapid growth, and the production of toxic secondary metabolites. Rock-inhabiting black fungi colonize – alone or within microbial communities (subaerial biofilms) – oligotrophic, exposed surfaces such as rocks, stone monuments, and photovoltaic panels, where competition from fast-growing saprobes is minimal. To understand how these fungi acquire iron, we combined comparative genomics with targeted gene deletions in the model species Knufia petricola. Genome analysis revealed a reduced repertoire of iron acquisition-related genes compared to those of pathogenic relatives: a single reductive iron assimilation (RIA) complex, one non-ribosomal peptide synthetase (NRPS) for siderophore biosynthesis, and absence of vacuolar iron transporters. Functional assays demonstrated that K. petricola primarily relies on RIA, mediated by FTR1–FET1, and secondarily on siderophore-mediated iron acquisition (SIA) via NPS1. Mutants lacking both systems were nearly non-viable under iron limitation, confirming that RIA and SIA are the only relevant uptake routes under laboratory conditions, that simulate the free-living lifestyle. Cross-feeding and chemotropism assays indicated secretion of an extracellular siderophore enabling growth toward the iron-containing mineral olivine. This siderophore, however, failed to mobilize iron from strong chelators such as BPS and EDTA, and its chemical nature remains unknown. Although melanin adsorbs and reduces iron, results on deletion mutants showed that melanin does not contribute to iron uptake or chelator resistance, functioning instead as a passive iron sink. Sensitivity assays revealed unusually low minimal inhibitory concentrations (MICs) for these chelators in K. petricola and other rock-inhabiting fungi, suggesting limited iron acquisition and storage capacity. These findings highlight the vulnerability of rock-inhabiting fungi to iron depletion and suggest that strong iron chelators could serve as an effective strategy to inhibit fungal colonization of human-made surfaces. T2 - Annual Conference of the Association for General and Applied Microbiology (VAAM) 2026 CY - Berlin, Germany DA - 22.03.2026 KW - Material colonization KW - Knufia petricola KW - Iron chelation PY - 2026 AN - OPUS4-65751 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -