Co-cultivation Approach and Untargeted Metabolomics in the Search for New Secondary Metabolites from Endophytic Fungi

Fungal endophytes are fungi living within the internal tissues of a host-plant, without causing any symptoms. Such microorganisms develop interactions not only with their host-plant but also with the entire microbiome of the host [1]. These organisms, and especially those isolated from plants of high biodiversity areas, are arousing researchers interest since they represent a relatively untapped renewable source of novel secondary metabolites [2]. Nevertheless, as micromycetes can modulate their metabolome very fast, depending on their environment, some endophytes lose their ability to produce compounds of interest in standard laboratory conditions [3]. Thus, different strategies have been investigated to induce the production of these metabolites, via the activation of silent genes. Such methods include the addition of epigenetic modifier or a modification of nutrients into the culture medium, but also the co-cultivation of endophytes. This last approach may induce the activation of some metabolic pathway leading to the production of bioactive metabolites, in response to the interactions between the species [4]. In order to search for new bioactive compounds from fungal endophytes, we investigated two fungal strains isolated from a South American plant, and belonging to the Phomopsis and Colletotrichum genera. These strains were both cultured in axenic conditions and as co-cultures. Ethyl acetate extractions of the cultures were performed and extracts were analysed by Ultra high-performance-liquid-chromatography coupled to high resolution mass spectrometry (UHPLC-HRMS). Chemical fingerprints obtained by untargeted metabolomics showed that the co-cultivation modified the metabolism of the strains and induced the production of new secondary metabolites. In vitro bioactivity of these extracts against Plasmodium falciparum, Leishmania infantum and VERO cells is under investigation, such as the isolation and characterization of the co-cultivation induced compounds.