Non-Obligate Pairwise Metabolite Cross-Feeding Suggests Ammensalic Interactions Between Bacillus and Aspergillus Species

Metabolite trade-offs at bacterial-fungal interfaces determine their ecological interactions. We designed a non-obligate pairwise metabolite cross-feeding (MCF) between Bacillus and Aspergillus . Cross-feeding Aspergillus metabolites (MCF-1) affected higher growth and biofilm formation in Bacillus . LC-MS-based multivariate analyses (MVA) showed marked variations in the endogenous metabolite profiles between the cross-fed and control Bacillus . We observed and validated that Aspergillus -derived oxylipins were rapidly depleted in Bacillus cultures concomitant with lowered secretion of cyclic lipopeptides (CLPs). Conversely, Bacillus extracts cross-fed to Aspergillus (MCF-2) diminished its mycelial growth and conidiation. Fungistatic effects of Bacillus -derived cyclic surfactins were temporally reduced following their hydrolytic linearization. MVA highlighted disparity between the cross-fed (MCF-2) and control Aspergillus cultures with marked variations in the oxylipin levels. We conclude that the pairwise MCF selectively benefitted Bacillus while suppressing Aspergillus , which suggests their ammensalic interaction. Widening this experimental pipeline across tailored communities may help model and simulate BFIs in more complex microbiomes.