Antibacterial potential of endolichenic fungi from lichen Usnea

Abstract

Lichens are unique organisms with medicinal benefits. However, lichens and endolichenic fungi in the Philippines are relatively less explored. In this study, the host lichen Usnea samples were collected from Mt. Talinis, Valencia, Negros Oriental and were surface sterilized for the isolation of endolichenic fungi. The endolichenic fungi were grown in culture, and secondary metabolites were extracted using ethyl acetate. The antibacterial activities of the crude culture extracts were analyzed against Acinetobacter baumannii, Enterococcus faecium, Klebsiella pneumoniae, Pseudomonas aeruginosa, Pantoea agglomerans, and Staphylococcus aureus through disk diffusion assay. Following morphological characterization, the host lichens were identified as Usnea baileyi, U. barbata, U. bismolliuscula, U. chaetophora, U. cornuta, and U. longissima, from which six endolichenic fungi were chosen. Results of the paper disk diffusion assay showed that Oidiodendron sp. inhibited the growth of Klebsiella pneumoniae (30 mm ZOI), and Geotrichum sp. inhibited the growth of Pantoea agglomerans (16 mm ZOI). Our study confirms that endolichenic fungi isolated from the fruticose lichen Usnea can be a promising source of secondary metabolites with antibacterial activity.