Browsing by Autor "Mahmoud Sayed"

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Identification, Characterization, and Antibacterial Evaluation of Five Endophytic Fungi from Psychotria poeppigiana Müll. Arg., an Amazon Plant
(Multidisciplinary Digital Publishing Institute, 2024) Sonia Mendieta-Brito; Mahmoud Sayed; Eunjung Son; Dong-Seon Kim; Marcelo Dávila; Sang‐Hyun Pyo
Endophytic fungi, residing within plants without causing disease, are known for their ability to produce bioactive metabolites with diverse properties such as antibacterial, antioxidant, and antifungal activities, while also influencing plant defense mechanisms. In this study, five novel endophytic fungi species were isolated from the leaves of Psychotria poeppigiana Müll. Arg., a plant from the Rubiaceae family, collected in the tropical Amazon region of Bolivia. The endophytic fungi were identified as a Neopestalotiopsis sp., three Penicillium sp., and an Aspergillus sp. through 18S ribosomal RNA sequencing and NCBI-BLAST analysis. Chemical profiling revealed that their extracts obtained by ethyl acetate contained terpenes, flavonoids, and phenolic compounds. In a bioautography study, the terpenes showed high antimicrobial activity against Escherichia coli. Notably, extracts from the three Penicillium species exhibited potent antibacterial activity, with minimum inhibitory concentration (MIC) values ranging from 62.5 to 2000 µg/mL against all three pathogens: Escherichia coli, Staphylococcus aureus, and Enterococcus faecalis (both Gram-positive and Gram-negative bacteria). These findings highlight the potential of these endophytic fungi, especially Penicillium species as valuable sources of secondary metabolites with significant antibacterial activities, suggesting promising applications in medicine, pharmaceuticals, agriculture, and environmental technologies.
Identification, characterization, antimicrobial activity and biocontrol potential of four endophytic fungi isolated from Amazonian plants
(Nature Portfolio, 2025) Sonia Mendieta-Brito; Mahmoud Sayed; Faqiha Ali Hamza; Eunjung Son; Dong-Seon Kim; G. Plata; Marcelo Dávila; Sang‐Hyun Pyo
Endophytic fungi, which reside within plants without causing disease, are recognized for their ability to produce bioactive metabolites with antibacterial, antifungal, and antioxidant properties, as well as their role in enhancing plant defense mechanisms. Due to these valuable traits, endophytic fungi have attracted significant attention in biotechnology and microbiology. The four endophytic fungal strains were isolated from the leaves of four Amazonian plant species—Piper heterophyllum Ruiz & Pav. (Paichané negro), Peperomia sp., Faramea multiflora A. Rich. ex DC.(Yuracaré), and Dictyoloma vandellianum A. Juss. (Sombrerillo). Molecular identification via 18 S rDNA sequencing and NCBI-BLAST analysis, as well as morphological characterization, were carried out for the isolates. Ethyl acetate extracts were obtained from both the growth medium and the fungal biomass. Thin-layer chromatography (TLC) combined with various staining techniques was used to identify the main groups of chemical compounds present in the extracts. The extracts were then assessed for antibacterial activity through a minimum inhibitory concentration (MIC) assay. The antagonistic potential of four endophytic fungi was evaluated through confrontation with phytopathogenic fungi using the dual culture plate assay. The results from molecular and morphological identification revealed two Aspergillus strains (SMB-18 and SMB-22), one Fusarium strain (SMB-20), and one Alternaria strain (SMB-28). Chemical profiling revealed a diverse composition, including carotenoids, terpenes, flavonoids, and phenolic compounds. The MIC assay demonstrated strong antibacterial activity against Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis, and Propionibacterium acnes), with MIC values ranging from 15.6 to 500 µg/mL. Additionally, antagonistic and biocontrol assays using dual-culture tests showed strong antifungal activity. Strains SMB-18, SMB-20, and SMB-22 effectively inhibited Helminthosporium sp. (58–80%), Fusarium oxysporum (37–50%), and Fusarium solani (51–57%), the well-known phytopathogenic fungi that affect potato crops. These findings highlight the potential of Amazonian endophytic fungi as sources of bioactive metabolites with promising applications in agriculture, medicine, and biotechnology, reinforcing the importance of biodiversity in bioprospecting.