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Screen the fungal diversity of Basidiomycota, the sister division of Ascomycota, could be efficient to find new antibiotics
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Edité par CCSD -
International audience. In the context of antibacterial resistance, the needs of new antibacterial is still urgent. The high potential of Fungi in bioactive metabolites is well known, especially for Ascomycota. However, the few studies done with Basidiomycota were always based on sporophores harvests and extractions. This is a bottleneck for original metabolites discoveries, and pressure environmental resources. In this purpose, we study fungal secretions and stress adaptation of Basidiomycota to trigger their secondary metabolites production and highlight their antibacterial activities with a focus on fungal Antimicrobial Peptides (f-AMP) especially. Genomic organization of f-AMP are not well known, and targeted ad/or in silico studies are not efficient. Thus, other secondary metabolites could also be secreted and antibacterial. In consequences, we set a non-targeted approach.Briefly, after a prescreening of 70 fungal strains, we focused on the <10kDa fraction of fungal secretomes to confirm and evaluate their antibacterial properties. The <10 kDa fraction allowed to hypothesis and focus on f-AMP. After confirming the antibacterial activities, Fungal AMP will be identified with HPLC-MS.MethodsWe used E. coli (ATCC 25922) as a bacterial model, and 70 fungal strains from the Cirm-cf collection (>3000 fungal strains, cirm-fungi.fr). The prescreening was done using agar coculture experiment. One part of a Petri dish was inoculated with the Fungi, and the other side with bacteria (normalized inoculum). As in classic antibacterial tests, diffusible antibacterials create an inhibition zone on the bacteria. Antibacterial fungal strains were selected and cultivated on liquid medium. We used <10 kDa secretome lyophilizates, respectively, to confirm the antibacterial activity and to evaluate the Minimum Inhibition Concentration (MIC) against E. coli following EUCAST recommendations, and against WHO’s priorities resistant bacteria (ESKAPE). We will use Mass Spectrometry with the best candidates to identify the f-AMP.ResultsThe pre-screening showed that 30% of the fungal strains revealed antibacterial activity. The method showed already known activity (i.e.: Fomitopsis betulina) but also revealed new activities faster than the liquid method (7 days versus 21 days). So far, concentrates did not reveal more antibacterial activity, but confirm all those detected on agar cocultures. The <10 kDa fraction reveal better antibacterial activity than the >10 kDa fraction. The evaluation of the Minimum Inhibition Concentration is under investigation.ConclusionsCoculture method on agar medium is effective to highlight new antibacterial activity and is rapid, cheap, efficient for the screening of new antibacterial activities among Fungal biodiversity. Our study is a medium scale screening for antibacterial activities of Basidiomycota’s mycelium and confirmed its potential and the relevance of looking for f-AMP in this fungal division.
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