AUTHOR=Wang Huan , Liu Ziyue , Duan Fangfang , Chen Yan , Qiu Kaidi , Xiong Qin , Lin Huiting , Zhang Jun , Tan Haibo 

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

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1172629

DOI=10.3389/fmicb.2023.1172629

ISSN=1664-302X

ABSTRACT=<p>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 <italic>Escherichia coli</italic> (<italic>E. coli</italic>), methicillin-resistant <italic>Staphylococcus aureus</italic> (MRSA), and <italic>Xanthomonas citri</italic> subsp. <italic>citri</italic> (<italic>Xcc</italic>) were also performed for the EtOAc extracts of these strains. As a result, the extracts of both <italic>Geotrichum</italic> sp. (gc-1-127-30) and <italic>Diaporthe biconispora</italic> (gc-1-128-79) demonstrated significant antibacterial activities against <italic>Xcc</italic>, and the MIC value for the extract of <italic>Colletotrichum gloeosporioides</italic> against MRSA was low to 62.5 μg/mL. Moreover, the chemical components of the extracts of <italic>Colletotrichum</italic> sp., <italic>Diaporthe biconispora</italic>, and <italic>Annulohypoxylon atroroseum</italic> were primarily investigated, and they successfully led to the isolation of 24 compounds involving a new botryane sesquiterpene. Among the isolated products, compound <bold>2</bold> showed significant inhibitory activities toward SA, MRSA, <italic>E. coli</italic>, and <italic>Xcc</italic> 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.</p>