Isolation, identification, and antibacterial evaluation of endophytic fungi from Gannan navel orange

Abstract

Gannan navel orange is a famous brand in China but the isolation of its endophytic fungi was rarely reported. In this study, a total of 54 strains of endophytic fungi were successfully isolated from the pulp, peel, twig, and leaf of Gannan navel orange; they were successfully identified to belong to 17 species of 12 genera. All these strains were fermented using potato-dextrose agar (PDA) medium, and their secondary metabolites were then extracted with ethyl acetate (EtOAc). The antibacterial assays of Escherichia coli (E. coli), methicillin-resistant Staphylococcus aureus (MRSA), and Xanthomonas citri subsp. citri (Xcc) were also performed for the EtOAc extracts of these strains. As a result, the extracts of both Geotrichum sp. (gc-1-127-30) and Diaporthe biconispora (gc-1-128-79) demonstrated significant antibacterial activities against Xcc, and the MIC value for the extract of Colletotrichum gloeosporioides against MRSA was low to 62.5 μg/mL. Moreover, the chemical components of the extracts of Colletotrichum sp., Diaporthe biconispora, and Annulohypoxylon atroroseum were primarily investigated, and they successfully led to the isolation of 24 compounds involving a new botryane sesquiterpene. Among the isolated products, compound 2 showed significant inhibitory activities toward SA, MRSA, E. coli, and Xcc with MIC values of 12.5, 3.1, 125, and 12.5 μg/mL, respectively. This study revealed that the endophytic fungi of Gannan navel orange showed high potency to produce secondary metabolites with significant antibacterial effects.

Identification and Characterization of a Plant Endophytic Fungus Paraphaosphaeria sp. JRF11 and Its Growth-Promoting Effects

“…Firstly, the washed samples were placed in a 10 mL centrifuge tube and repeatedly shaken with sterile water. Secondly, the samples were cleaned and sterilized using a 75% ethanol solution, and the supernatant was removed following natural sedimentation [19][20][21][22][23]. Then, samples were rinsed three times with sterile water to eliminate the ethanol.…”

Microbial and Plant-Based Compounds as Alternatives for the Control of Phytopathogenic Bacteria

“…This finding highlights the potential of fungal-derived compounds as effective agents against bacterial pathogens. Another study [33] investigated the antibacterial activity of 17 morphotypes of orange endophytic fungi, where several strains belonging to the genera Fusarium, Diaporthe, Colletotrichum, Geotrichum, Penicilium and Polyporus exhibited significant antibacterial activity against X. citri subsp. citri, the causative agent of citrus canker.…”

Genotype, Tannin Capacity, and Seasonality Influence the Structure and Function of Symptomless Fungal Communities in Aspen Leaves, Regardless of Historical Nitrogen Addition

“…Sanger sequencing subsequently enabled the molecular determination of culturable colonies [41,42]. Today, metabarcoding and shotgun sequencing of eDNA has widely replaced culturing as a way to assess endophyte community composition independently of culturing; and high-throughput metagenomic sequencing techniques are now standardly used to characterize the presence of fungal DNA strands in environmental samples [43]. The ampli cation and sequencing of conserved DNA regions with high interspeci c and low intraspeci c variation, are followed by downstream bioinformatic analyses, to reveal the diversity, composition, and function of leaf-associated fungal communities [42].…”