Co-culture of the bacterium Pseudomonas aeruginosa with the fungus Fusarium tricinctum induces bacterial antifungal and quorum sensing signaling molecules

Co-cultivation of viable cells of the human pathogenic bacterium Pseudomonas aeruginosa with the endophytic fungus Fusarium tricinctum induced silent bacterial biosynthetic gene clusters. Visual and chemical inspection of the co-cultures by comparison with the axenic cultures showed a clear reaction of P. aeruginosa towards its fungal competitor which was reflected by the deep greenish coloration of the co-cultures. Inspection of the HPLC chromatograms of the co-cultures revealed the induction of the pseudomonal quorum sensing molecule 2-heptyl-4-hydroxy-quinolone (HHQ) along with the antifungal phenazine alkaloids, phenazine-1-carboxylic acid (PCA) and phenazine-1-carboxamide (PCN), which are well-known metabolites of P. aeruginosa. The latter compounds were not detected in axenic bacterial cultures. In contrast to P. aeruginosa, no metabolic responses were detected for F. tricinctum which is in sharp contrast to previous co-culture experiments with this fungus using other bacteria.