Abstract
The in vitro antibacterial activity of the endophytic fungus Aspergillus neobridgeri PLR9 (isolated from the plant Pistacia lentiscus) against a wide range of tested bacteria were studied. The maximum inhibitory activity was found on malt extract agar medium with a mean inhibitory zone of 11.3 mm (p<0.05). The ethyl acetate extract showed a significant inhibitory zone of 13.4 mm (p<0.05), followed by dichloromethane 9.1 mm. Whereas, n-hexane extract showed no activity. The largest inhibition zones were observed against Staphylococcus aureus 3, S. aureus 5 and Escherichia coli 1 with 21.0 mm of diameter. The MIC's were ranged between 312.5 and 1,250 μg/mL. The MBC's were ≤2500 μg/mL for most Gram positive bacteria and ≥2500 μg/mL for most Gram negative bacteria. Time kill assay study against the Enterococcus faecium showed a bactericidal effect at 4x MIC and bacteriostatic against Acinetobacter baumannii at different concentrations. Moreover, it is the first report, PLR9 isolated as endophyte and studied for their antimicrobial activity.
Highlights
Several studies have shown the ability of different species of endophytic fungi to inhibit pathogenic microorganisms, for example; Aspergillus terreus and Aspergillus tubingensis (Yadav et al, 2016), Diaporthe terebinthifolii LGMF907, Phomopsis prunorum (Qu et al, 2020), P. griseofulvum TPL25 (Luo et al, 2015), Alternaria GFAV15 (Yadav et al, 2020), Alternariatenuissima OE7 (Chatterjee et al, 2019) and Trichoderma koningiopsis QA-3 (Shi et al, 2020)
PLR9 colony exhibited a rapid growth on malt extract agar and potato dextrose agar
Phylogenetic analysis of sequence parts of ribosomal RNA, BenA and CaM genes indicated that PLR9 is a member of Circumdati section and very close to the A. neobridgeri species supported by bootstrap values for likelihood (ML >99 %)
Summary
Endophytic fungi are present in all plant species studied so far and they can be found in the internal tissues of roots, stems, leaves, flowers, fruits or seeds (Tanapichatsakul et al, 2018). Novel chemical skeletons of secondary metabolites have antimicrobial, antiparasitic, cytotoxic, anti-inflammatory, antitumor, antioxidant and neuroprotective activities (Malhadas et al, 2017) Due to their ability to produce of a wide range biologically active compounds and their ability to inhibit several pathogens in the plant, animal and human; endophytes from medicinal plants are becoming more interesting to be explored and are considered a promising resource for new bioactive compounds (Atiphasaworn et al, 2017). Several studies have shown the ability of different species of endophytic fungi to inhibit pathogenic microorganisms, for example; Aspergillus terreus and Aspergillus tubingensis (Yadav et al, 2016), Diaporthe terebinthifolii LGMF907 (de Medeiros et al, 2018), Phomopsis prunorum (Qu et al, 2020), P. griseofulvum TPL25 (Luo et al, 2015), Alternaria GFAV15 (Yadav et al, 2020), Alternariatenuissima OE7 (Chatterjee et al, 2019) and Trichoderma koningiopsis QA-3 (Shi et al, 2020)
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