Aromatic Polyketides from a Symbiotic Strain Aspergillus fumigatus D and Characterization of Their Biosynthetic Gene D8.t287.

Yi Hua,Rui Pan,Huawei Zhang,Jianwei Chen,Xuelian Bai,Hong Wang,Bin Wei

doi:10.3390/md18060324

Yi Hua, Rui Pan + Show 5 more

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https://doi.org/10.3390/md18060324

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Abstract

The chemical investigation of one symbiotic strain, Aspergillus fumigatus D, from the coastal plant Edgeworthia chrysantha Lindl led to the isolation of eight compounds (1–8), which were respectively identified as rubrofusarin B (1), alternariol 9-O-methyl ether (2), fonsecinone D (3), asperpyrone A (4), asperpyrone D (5), fonsecinone B (6), fonsecinone A (7), and aurasperone A (8) by a combination of spectroscopic methods (1D NMR and ESI-MS) as well as by comparison with the literature data. An antimicrobial assay showed that these aromatic polyketides exhibited no remarkable inhibitory effect on Escherichia coli, Staphyloccocus aureus and Candida albicans. The genomic feature of strain D was analyzed, as well as its biosynthetic gene clusters, using antibiotics and Secondary Metabolite Analysis Shell 5.1.2 (antiSMASH). Plausible biosynthetic pathways for dimeric naphtho-γ-pyrones 3–8 were first proposed in this work. A non-reducing polyketide synthase (PKS) gene D8.t287 responsible for the biosynthesis of these aromatic polyketides 1–8 was identified and characterized by target gene knockout experiment and UPLC-MS analysis.

Highlights

Symbiotic microorganisms are generally acknowledged as a significant source of structurally novel and biologically diverse chemicals, including alkaloids, terpenoids, polyketides, depsipeptides and perylenequinonoid derivatives [1]
Biological tests indicated that no compound exhibited exhibited potent antimicrobial activity against human pathogenic microbes Escherichia coli, Staphyloccocus potent antimicrobial activity against human pathogenic microbes Escherichia coli, Staphyloccocus aureus and Candida albicans with minimum inhibitory concentration (MIC) values of ≥100 μM
The results indicated that strain D was sensitive to hygromycin B (Hyg) and G418, and its growth was halted on Potato Dextrose Agar (PDA) containing at least 25 μg·mL−1 of Hyg or 150 μg·mL−1 of G18 (Figure S2)

Summary

Introduction

Symbiotic microorganisms are generally acknowledged as a significant source of structurally novel and biologically diverse chemicals, including alkaloids, terpenoids, polyketides, depsipeptides and perylenequinonoid derivatives [1]. The genus Aspergillus possesses strong potential to biosynthesize cryptic secondary metabolites (SMs) with prominent biological properties, ranging from antioxidant, to anti-bacteria, to anti-cancer drugs [2,3,4]. Strain D was isolated from coastal plant Edgeworthia chrysantha Lindl. Bioassay-guided fractionation of the ethyl acetate extract of strain D, cultured in salted and unsalted Czapek media, previously led to the isolation of seven antimicrobial agents, including bisdethiobis (methylthio) gliotoxin, gliotoxin, pseurotin A, and spirotryprostatins A and. We reported the discovery of eight known aromatic polyketides (1–8) (Figure 1) from strain D when grown on a rice

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