Abstract
The growing problem of antimicrobial resistance (AMR) has become a major and urgent threat to public health causing significant difficulties with persistent disease prevention and treatment. Despite some advances in the past few decades to try and solve this issue, AMR is still progressing gradually. In response to this challenge, there has been a transformation in the global trend of synthetic compounds towards re-examining microbial secondary metabolites. This shift has been propelled by advancements in genomics and metabolomics tools, which have enhanced screening capabilities. The present study aimed to combine genomic and untargeted metabolomic data to predict the biosynthetic gene cluster that encodes antibacterial activities in filamentous fungi, Alternaria alternata P02PL2 isolated from Sclerocarya birrea. The one strain many compounds (OSMAC) approach was carried out to induce the production of secondary metabolites in A. alternata P02PL2 by cultivating it in eight different media (1% malt extract broth, potato dextrose broth, YPSS, YESD, PYG, oatmeal, rice, and a mixture of rice and oatmeal). Preliminary screening of the obtained fungal crude extracts revealed that oatmeal media extract had significant antibacterial activity against Staphylococcus aureus ATCC 25923 and Methicillin-resistant Staphylococcus aureus (MRSA) 5627679. In contrast, potato dextrose broth extract exhibited antibacterial activity against Multidrug-resistant Pseudomonas 5625574. Solid phase extraction was carried out to fractionate these fungal crude extracts, a total of 15 fractions were obtained per media. Three fractionated extracts exhibited activity against MDR Pseudomonas 5625574 with an MIC ranging from 0.25 to 0.5 mg/mL, and two fractionated extracts exhibited activity against S. aureus ATCC 25923 with an MIC ranging from 0.25 to 0.5 mg/mL. High-resolution liquid chromatography-tandem mass spectrometry (HRLCMS/MS) analysis of the fractionated extracts identified 20 secondary metabolites distributed amongst the five fractions. Furthermore, the whole genome of A. alternata P02PL2 was sequenced, assembled, and annotated before being subjected to fungiSMASH analysis, revealing 29 secondary metabolite biosynthetic gene clusters distributed across 12 categories. Therefore, from the obtained results, it can be inferred that A. alternata P02PL2, isolated from S. birrea, can be a source of new compounds used for the synthesis of drugs.