Scedosporium/Lomentospora Species Induce the Production of Siderophores by Pseudomonas aeruginosa in a Cystic Fibrosis Mimic Environment

Over the last years, the interkingdom microbial interactions concerning bacteria and fungi cohabiting and/or responsible for human pathologies have been investigated. In this context, the Gram-negative bacterium and fungal species belonging to the genera are widespread, multidrug-resistant, emergent, opportunistic pathogens that are usually co-isolated in patients with cystic fibrosis. The available literature reports that can inhibit the in vitro growth of species; however, the complex mechanisms behind this phenomenon are mostly unknown. In the present work, we have explored the inhibitory effect of bioactive molecules secreted by (3 mucoid and 3 non-mucoid strains) on ( = 6 strains), ( = 3), ( = 6) and ( = 6) under cultivation in a cystic fibrosis mimic environment. It is relevant to highlight that all bacterial and fungal strains used in the present study were recovered from cystic fibrosis patients. The growth of species was negatively affected by the direct interaction with either mucoid or non-mucoid strains of . Moreover, the fungal growth was inhibited by the conditioned supernatants obtained from bacteria-fungi co-cultivations and by the conditioned supernatants from the bacterial pure cultures. The interaction with fungal cells induced the production of pyoverdine and pyochelin, 2 well-known siderophores, in 4/6 clinical strains of . The inhibitory effects of these four bacterial strains and their secreted molecules on fungal cells were partially reduced with the addition of 5-flucytosine, a classical repressor of pyoverdine and pyochelin production. In sum, our results demonstrated that distinct clinical strains of can behave differently towards species, even when isolated from the same cystic fibrosis patient. Additionally, the production of siderophores by was induced when co-cultivated with species, indicating competition for iron and deprivation of this essential nutrient, leading to fungal growth inhibition.