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Published on: February 14, 2018
Antibacterial Potential of Patagonian Fungi: Screening, Metabolite Profiling, and Novel Findings
Daiana Andrea Calderón1,2, Enrique Andrés Del Vigo1,2, Gabriela Myriam Cabrera2,3
1Andean Patagonian Forest Research and Extension Center (CIEFAP), Esquel, Chubut, Argentina.
Abstract:
Patagonian fungi are an underexplored source of secondary metabolites with promising antimicrobial potential, a topic of growing relevance given the global spread of antibiotic resistance. In this study, we evaluated the antibacterial activity of 85 fungal isolates from Ascomycota, Basidiomycota, and Mucoromycota; 49 fungal conditioned media displayed inhibition against both Gram-positive and Gram-negative bacteria in a 96-well OD₆₀₀ microplate assay. Staphylococcus aureus, Bacillus subtilis, and Lysinibacillus sphaericus were the most sensitive Gram-positive strains, while Klebsiella pneumoniae showed the highest susceptibility among Gram-negative species. Complete inhibition of S. aureus was achieved in the conditioned-media assay by Arthrinium arundinis, Cladosporium sp., Graphilbum sp. 2, and Postia balsamea, with Graphilbum representing a previously unreported antimicrobial genus. In the conditioned-media microplate assay, potent antibacterial activity (> 99.5%) against all 5 tested bacterial strains was recorded for Allantophomopsis sp., Aureobasidium sp., Coniochaeta sp., Graphilbum sp. 2, and Mucor pyriformis, most of which have not been previously associated with antibacterial activity against Bacillus or Klebsiella genus. Marked inhibition of S. aureus and K. pneumoniae laboratory strains was observed for Arachnopeziza aurelia, Coprinellus sp., and Poria sp. Remarkably, Umbelopsis (Mucoromycota) inhibited all bacteria strains tested in the conditioned-media assay, revealing previously unreported antibacterial activity for this genus. Several extracts retained measurable but variable antibacterial activity in disk-diffusion assays producing inhibition zones against selected bacterial strains. Chemical profiling of active extracts revealed cyclic dipeptides (diketopiperazines) as recurrent metabolites and a unique family of unknown compounds exclusively found in Graphilbum sp. 2, representing its first metabolomic characterization. Overall, these results identify Patagonian fungi as a valuable reservoir of bioactive metabolites with potential as new natural antimicrobial agents.
Insights
Patagonian fungi yield novel antimicrobial compounds effective against resistant bacteria like Staphylococcus aureus and Klebsiella pneumoniae. This research highlights fungi as a promising source for new natural antibiotics.
Area of Science:
- Microbiology
- Natural Products Chemistry
- Mycology
Background:
- Antibiotic resistance is a growing global health threat.
- Fungi, particularly from underexplored regions like Patagonia, are a rich source of bioactive secondary metabolites.
- Previous research has identified antimicrobial properties in some fungal species, but Patagonian fungi remain largely uninvestigated.
Purpose of the Study:
- To evaluate the antibacterial activity of fungal isolates from Patagonia.
- To identify specific fungal species and their metabolites with potent antimicrobial properties.
- To explore the potential of these natural products as novel antimicrobial agents.
Main Methods:
- Screening of 85 fungal isolates from Ascomycota, Basidiomycota, and Mucoromycota.
- Assessing antibacterial activity using 96-well microplate assays with fungal conditioned media.
- Utilizing disk-diffusion assays for validation and chemical profiling of active extracts.
Main Results:
- 49 fungal conditioned media exhibited inhibition against Gram-positive and Gram-negative bacteria.
- Staphylococcus aureus, Bacillus subtilis, Lysinibacillus sphaericus, and Klebsiella pneumoniae showed high susceptibility.
- Several fungal genera, including Graphilbum and Umbelopsis, demonstrated significant, previously unreported, antibacterial activities.
- Cyclic dipeptides and unique compounds from Graphilbum sp. 2 were identified.
Conclusions:
- Patagonian fungi represent a valuable resource for discovering new natural antimicrobial compounds.
- The identified fungal isolates and their metabolites hold potential for developing novel therapeutic agents against resistant bacteria.
- Further investigation into the unique compounds from Graphilbum sp. 2 is warranted.
