Monitoring metabolites from Schizophyllum commune interacting with Hypholoma fasciculare combining LESA–HR mass spectrometry and Raman microscopy

Microbial competition for territory and resources is inevitable in habitats with overlap between niches of different species or strains. In fungi, competition is brought about by antagonistic mycelial interactions which alter mycelial morphology, metabolic processes, secondary metabolite release, and extracellular enzyme patterns. Until now, we were not able study in vivo chemical interactions of different colonies growing on the same plate. In this report, we developed a fast and least invasive approach to identify, quantify, and visualize co culture-induced metabolites and their location of release within Schizophyllum commune. The pigments indigo, indirubin, and isatinwere used as examples to showsecondary metabolite production in the interaction zone with Hypholoma fasciculare. Using a combinatory approach of Raman spectroscopy imaging, liquid extraction surface analysis (LESA), and high-resolution mass spectrometry, we identified, quantified, and visualized the presence of indigo and indirubin in the interaction zone. This approach allows the investigation of metabolite patterns between wood degrading species in competition to gain insight in community interactions, but could also be applied to other microorganisms. This method advances analysis of living, still developing colonies and are in part not destructive as Raman spectroscopy imaging is implemented.