Amphotericin B as part of a chemical complex behind two endophytic microorganisms interaction

Introduction During our work on endophytic microorganisms from the Brazilian medicinal plant, Lychnophora ericoides, we found that the antifungal compound amphotericin B, produced by endophytic Streptomyces albospinus RLe7, is not the only compound involved in the inhibition of endophytic Coniochaeta sp. FLe4. Methods-materials S. albospinus RLe7 and Coniochaeta sp. FLe4 were cocultured on ISP2 at 30 oC until required time for mass spectrometry analysis. After grown, the regions of interest were prepared for MALDI-IMS as well as for MS/MS analysis. Molecular networking was created by submitting the MS data set to the GnPS (http://gnps.ucsd.edu/ProteoSAFe/static/gnps-splash.jsp) plataform and visualized using Cytoscape (http://www.cytoscape.org/). Results and discussion A red pigmentation was observed for the fungus Coniochaeta sp. FLe 4 when coculture with S. albospinus RLe 7. By using several tools for the analysis of MS data, it was confirmed the production of the amphotericin B as well as other possible related compounds accordingly to their MS/MS fragmentation pattern. Timecourse MALDI IMS showed that amphotericin B is not the only responsible for the antifungal activity of S. albospinus RLe 7, but a group of compounds in the region of m/z 800-900 seem to be also involved before amphotericin B production begins. Continuous work is ongoing in order to completely identify the molecules involved in this microbial interaction. The efficiency of MS techniques and related tools for identification and hypotheses generation of biological role of natural products was demonstrated. Conclusion This results revealed the chemical complexity behind an actinobacterium-fungus interaction leading to the identification of the possible role of microbial metabolites. Keywords Amphotericin B, Streptomyces albospinus, Coniochaeta sp., endophyte, coculture. Financial support Authors are grateful to the Brazilian financial institutions FAPESP, CNPq, CEPID-CIBFar and to the UCSD.