Antibacterial activity of endophytic fungi isolated from Sceletium tortuosum L. (Kougoed)

Abstract

Endophytic fungi have the ability to co-exist with their host plants without causing any harm and are beneficial to both the plant and the fungi. The current study determined the antimicrobial properties and identify the chemical compounds of secondary metabolites produced by endophytic fungi isolated from Sceletium tortuosum L. A total of 60 endophytic fungi produced secondary metabolites that were detected after fermentation and extraction. Antibacterial properties of the secondary metabolites were determined using the disc diffusion assay against pathogenic environmental Gram-positive and Gram-negative bacteria as well as control stains. The chemical compounds were characterized by GC-MS. Overall, 15% of fungal extracts displayed narrow spectrum of activity against the bacteria strains. Despite this, none of the fungal extracts inhibited growth of Enterococcus faecalis (ATCC S1299) and Enterococcus gallinarum (ATCC 700425) while Bacillus cereus (ATCC 10876) was the most susceptible against the fungal extracts. Fusarium oxysporum (GG 008) with accession no. KJ774041.1 displayed significant antibacterial activity that was linked to high levels of 5-hydroxymethylfurfural (HMF) and octadecanoic acid as revealed by GC-MS. This study revealed the presence of bioactive secondary metabolites with antibacterial activities from fungi isolated from Sceletium tortuosum L.