title: Fungal Root Microbiome from Healthy and Brittle Leaf Diseased Date Palm Trees (Phoenix dactyliferaL.) Reveals a Hidden Untapped Arsenal of Antibacterial and Broad Spectrum Antifungal Secondary Metabolites.
abstract: In this study, we aimed to explore and compare the composition, metabolic diversity and antimicrobial potential of endophytic fungi colonizing internal tissues of healthy and brittle leaf diseased (BLD) date palm trees (Phoenix dactyliferaL.) widely cultivated in arid zones of Tunisia. A total of 52 endophytic fungi were isolated from healthy and BLD roots of date palm trees, identified based on internal transcribed spacer-rDNA sequence analysis and shown to represent 13 species belonging to five genera. About 36.8% of isolates were shared between healthy and diseased root fungal microbiomes, whereas 18.4 and 44.7% of isolates were specific to healthy and BLD root fungal microbiomes, respectively. All isolates were able to produce at least two of the screened enzymes including amylase, cellulase, chitinase, pectinase, protease, laccase and lipase. A preliminary screening of the isolates using disk diffusion method for antibacterial activity against four Gram-positive and three Gram-negative bacteria and antifungal activities against three phytopathogenic fungi indicated that healthy and BLD root fungal microbiomes displayed interesting bioactivities against examined bacteria and broad spectrum bioactivity against fungal pathogens. Some of these endophytic fungi (17 isolates) were fermented and their extracts were evaluated for antimicrobial potential against bacterial and fungal isolates. Results revealed that fungal extracts exhibited antibacterial activities and were responsible for approximately half of antifungal activities against living fungi. These results suggest a strong link between fungal bioactivities and their secondary metabolite arsenal. EtOAc extracts ofGeotrichum candidumandThielaviopsis punctulataoriginating from BLD microbiome gave best results againstMicrococcus luteusandBacillus subtiliswith minimum inhibitory concentration (MIC, 0.78 mg/mL) and minimum bactericidal concentration (6.25 mg/mL).G. candidumgave the best result againstRhizoctonia solaniwith MIC 0.78 mg/mL and minimum fungicidal concentration (MFC, 6.25 mg/mL). In conclusion, using plant microbiomes subjected to biotic stresses offers new endophytes with different bioactivities than those of healthy plants. Therefore, date palm endophytic fungi represent a hidden untapped arsenal of antibacterial and broad spectrum antifungal secondary metabolites and could be considered promising source of bioactive compounds with industrial and pharmaceutical applications.
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Science, University of Sfax Sfax, Tunisia.
authors.forename: Fedia B
authors.initials: FB
authors.lastname: Mefteh
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Science, University of Sfax Sfax, Tunisia.
authors.forename: Amal
authors.initials: A
authors.lastname: Daoud
authors.affiliation: Biotechnology, NextBiotechAgareb, Tunisia; Graduate School of Life and Environmental Sciences, Osaka Prefecture UniversitySakai, Japan.
authors.forename: Ali
authors.initials: A
authors.lastname: Chenari Bouket
authors.affiliation: Biotechnology, NextBiotech Agareb, Tunisia.
authors.forename: Faizah N
authors.initials: FN
authors.lastname: Alenezi
authors.affiliation: Biotechnology, NextBiotechAgareb, Tunisia; Department of Biology and Genetics, Institute of Biology, Zoology and Radiobiology, University of Veterinary Medicine and PharmacyKosice, Slovakia.
authors.forename: Lenka
authors.initials: L
authors.lastname: Luptakova
authors.affiliation: School of Science and Sport, University of the West of Scotland Paisley, UK.
authors.forename: Mostafa E
authors.initials: ME
authors.lastname: Rateb
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Science, University of SfaxSfax, Tunisia; College of Science and Arts in Baljurashi, Al Baha UniversityAl Bahah, Saudi Arabia.
authors.forename: Adel
authors.initials: A
authors.lastname: Kadri
authors.affiliation: Laboratory of Plant Biotechnology, Faculty of Science, University of Sfax Sfax, Tunisia.
authors.forename: Neji
authors.initials: N
authors.lastname: Gharsallah
authors.affiliation: Biotechnology, NextBiotechAgareb, Tunisia; Laboratory of Soil Biology, University of NeuchâtelNeuchâtel, Switzerland.
authors.forename: Lassaad
authors.initials: L
authors.lastname: Belbahri
keywords: antimicrobial activity; brittle leaf disease; date palm; endophytic fungi; enzymes; secondary metabolites