Deep-sea Fungus Research Articles

First evidence of the deep-sea fungus Oceanitis scuticella Kohlmeyer (Halosphaeriaceae, Ascomycota) from the Northern Hemisphere

Abstract We report on a collection of the deep-sea fungus Oceanitis scuticella from recently sunken wood at abyssal depth in the Northwest Pacific Ocean. The fungus was originally described as wood-associated from the Angola Basin. Subsequently, it was also found on sunken wood in the Southwest Pacific Ocean. Ascomata and ascospores of O. scuticella were examined by scanning electron microscopy and light microscopy. The phylogenetic affiliation of the fungus within the Halosphaeriaceae was demonstrated using partial nuclear internal transcribed spacer (ITS) regions and large subunit (LSU) rDNA sequencing. Slight morphological differences between this collection and previously described material were observed concerning ascomata shape, namely the drop-shaped cavity, the form of the hypostroma and the thickness of the peridium. In addition, the ascospores were smaller than those reported in previous collections. LSU rDNA phylogeny provided a good support for the placement of the NW Pacific Ocean sample within O. scuticella. The ITS rDNA sequence of the present collection differed from those of the earlier collections by 2.5–3%, a value accepted for intraspecific variation in fungi. Based on the present material, some factors interpreted as indicators for true deep-sea fungi, such as the absence of bark or co-existing xylophagic bivalves in sunken wood, are discussed and their importance is considered as limited.

Extracellular polysaccharide with novel structure and antioxidant property produced by the deep-sea fungus Aspergillus versicolor N2bc

An extracellular polysaccharide, N1, was obtained from the culture medium of the deep-sea fungus Aspergillus versicolor N2bc by a combination of ethanol precipitation, ion-exchange and gel filtration chromatography. N1 was a mannoglucogalactan with molecular weight of about 20.5kDa. Results of chemical and spectroscopic analyses, including Fourier-transform infrared, one- and two-dimensional nuclear magnetic resonance spectroscopy showed that the main chain of N1 consisted of →2)-α-d-Glcp-(1→, →2)-β-d-Glcp-(1→ and →6)-β-d-Manp-(1→ units, substituted at C-6 position of →2)-α-d-Glcp-(1→ units. The branches were composed of galactofuranose-oligosaccharides built up of →5)-β-d-Galf-(1→, →6)-β-d-Galf-(1→ and terminal β-d-Galf units. At an average, there were two branching points for every five sugar residues in the backbone. N1 possessed a high in vitro antioxidant activity as evaluated by scavenging assays involving superoxide, 1,1-diphenyl-2-picrylhydrazyl, hydroxyl radicals and reducing power. The investigation revealed that N1 was a novel antioxidant polysaccharide differing from previously described extracellular polysaccharides and could be a potential antioxidant.

20-Nor-isopimarane cycloethers from the deep-sea sediment-derived fungus Aspergillus wentii SD-310

Five new 20-nor-isopimaranes, asperethers A–E (1–5), were isolated from the deep-sea derived fungus Aspergillus wentii SD-310. These compounds possess a unique 6/6/6/5 tetracyclic system and exhibited cytotoxicity against several tumor cell lines.

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A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as chrysamide A from a deep-sea fungus Penicillium chrysogenum.

Antioxidative phenolic compounds from a marine-derived fungus Aspergillus versicolor

Bioassay-guided fractionation and chromatographic separation of a deep-sea fungus Aspergillus versicolor resulted in the isolation of 22 phenolic compounds, of which six were new natural products namely aspergilols A–F (1–6). The structures of the new compounds were determined through extensive spectroscopic analysis, including the ECD data and chemical conversion for the configurational assignment. Aspergilols A and B presented as a new scaffold with a C–C fusion of an anthraquinone and orcinol unit. The trolox equivalent antioxidant capacity (TEAC) assay indicated most of the phenolic compounds possessing antioxidant activities, while four compounds (12, 14, 21, and 22) exerted strong free-radical scavenging effects with the TEAC values around five folds more than trolox. In addition, an Nrf2-dependent luciferase reporter gene assay revealed that compounds 12–14 and 17–18 potentially activated the expression of Nrf2-regulated gene. The primary structure–activity relationship was discussed. These findings provided the evidence that the deep-sea derived microorganisms are the promising and new source for the discovery of antioxidant agents.

Spiromastilactones: A new class of influenza virus inhibitors from deep-sea fungus

A new class of phenolic lactones with trivial names of spiromastilactones A-M (1–13) was isolated from a deep-sea derived Spiromastix sp. fungus. Their structures featured by various chlorination at aromatic rings were determined on the basis of extensive spectroscopic analyses. An antiviral assay revealed that most of the tested compounds exert inhibitory activity against WSN influenza virus with low cytotoxicity, while the structure–activity relationships were discussed. Spiromastilactone D (4), a 5′-chloro-2′-methoxy substituted analogue, displayed the most potent to inhibit a panel of influenza A and B viruses in addition to drug-resistant clinical isolates. Mechanistic investigation resulted in that compound 4 bonded to hemagglutinin protein (HA), potentially at the spherical head, and disrupted the HA-sialic acid receptor interaction, that is essential for the attachment and entry of all influenza viruses. In addition, compound 4 also showed inhibitory effect toward viral genome replication via targeting viral RNP complex. The synergistic effects of 4 on both viral entry and replication assumed it to be a promising lead for the development of a new influenza inhibitor.

Effects of hydrostatic pressure on yeasts isolated from deep-sea hydrothermal vents

Hydrostatic pressure plays a significant role in the distribution of life in the biosphere. Knowledge of deep-sea piezotolerant and (hyper)piezophilic bacteria and archaea diversity has been well documented, along with their specific adaptations to cope with high hydrostatic pressure (HHP). Recent investigations of deep-sea microbial community compositions have shown unexpected micro-eukaryotic communities, mainly dominated by fungi. Molecular methods such as next-generation sequencing have been used for SSU rRNA gene sequencing to reveal fungal taxa. Currently, a difficult but fascinating challenge for marine mycologists is to create deep-sea marine fungus culture collections and assess their ability to cope with pressure. Indeed, although there is no universal genetic marker for piezoresistance, physiological analyses provide concrete relevant data for estimating their adaptations and understanding the role of fungal communities in the abyss. The present study investigated morphological and physiological responses of fungi to HHP using a collection of deep-sea yeasts as a model. The aim was to determine whether deep-sea yeasts were able to tolerate different HHP and if they were metabolically active. Here we report an unexpected taxonomic-based dichotomic response to pressure with piezosensitve ascomycetes and piezotolerant basidiomycetes, and distinct morphological switches triggered by pressure for certain strains.

Production and characterization of bioactive metabolites from piezotolerant deep sea fungus Nigrospora sp. in submerged fermentation.

To produce and characterize bioactive metabolites from piezotolerant marine fungus Nigrospora sp. in submerged fermentation. A distinct marine strain, Nigrospora sp. NIOT has been isolated from a depth of 800 m at the Arabian Sea. The 18S rRNA and internal transcribed spacers (ITS) analysis demonstrates its close association with the genus Nigrospora. Effect of pH, temperature, salinity, carbon source and amino acids was studied to optimize the fermentation conditions. Optimal mycelia growth and secondary metabolites production were observed at 6·0-8·0 pH, 20-30°C temperature, 7·5% salinity, sucrose as carbon source and tryptophan as amino acid source. The extracellular secondary metabolites exhibited high antimicrobial activities against both gram-positive and gram-negative pathogenic bacteria with minimal inhibitory concentration (MIC) values higher than 30 μg ml(-1). Strongest cytotoxicity was observed in all cell lines tested, GI50 (growth inhibition by 50%) was calculated to be 1·35, 3·2, 0·13 and 0·35 μg ml(-1) against U937, MCF-7, A673 and Jurkat, respectively. Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) analyses of secondary metabolites confirmed the production of antimicrobial and anticancer substances. A piezotolerant fungus Nigrospora sp. NIOT isolated from deep sea environment was successfully cultured under submerged fermentation. The secondary metabolites produced from this organism showed potent antimicrobial and anticancer activities with immediate application to cosmetics and pharmaceutical industries. This is the first study exploring Nigrospora sp. from 800 m in marine environment. This deep sea fungus under optimized culture conditions effectively produced bioactive secondary metabolites such as griseofulvin, spirobenzofuran and pyrone derivatives at higher concentrations.

Activation of dormant secondary metabolite production by introducing neomycin resistance into the deep-sea fungus, Aspergillus versicolor ZBY-3.

A new ultrasound-mediated approach has been developed to introduce neomycin-resistance to activate silent pathways for secondary metabolite production in a bio-inactive, deep-sea fungus, Aspergillus versicolor ZBY-3. Upon treatment of the ZBY-3 spores with a high concentration of neomycin by proper ultrasound irradiation, a total of 30 mutants were obtained by single colony isolation. The acquired resistance of the mutants to neomycin was confirmed by a resistance test. In contrast to the ZBY-3 strain, the EtOAc extracts of 22 of the 30 mutants inhibited the human cancer K562 cells, indicating that these mutants acquired a capability to produce antitumor metabolites. HPLC-photodiode array detector (PDAD)-UV and HPLC-electron spray ionization (ESI)-MS analyses of the EtOAc extracts of seven bioactive mutants and the ZBY-3 strain indicated that diverse secondary metabolites have been newly produced in the mutant extracts in contrast to the ZBY-3 extract. The followed isolation and characterization demonstrated that six metabolites, cyclo(d-Pro-d-Phe) (1), cyclo(d-Tyr-d-Pro) (2), phenethyl 5-oxo-l-prolinate (3), cyclo(l-Ile-l-Pro) (4), cyclo(l-Leu-l-Pro) (5) and 3β,5α,9α-trihydroxy-(22E,24R)-ergosta-7,22-dien-6-one (6), were newly produced by the mutant u2n2h3-3 compared to the parent ZBY-3 strain. Compound 3 was a new compound; 2 was isolated from a natural source for the first time, and all of these compounds were also not yet found in the metabolites of other A. versicolor strains. Compounds 1–6 inhibited the K562 cells, with inhibition rates of 54.6% (1), 72.9% (2), 23.5% (3), 29.6% (4), 30.9% (5) and 51.1% (6) at 100 μg/mL, and inhibited also other human cancer HL-60, BGC-823 and HeLa cells, to some extent. The present study demonstrated the effectiveness of the ultrasound-mediated approach to activate silent metabolite production in fungi by introducing acquired resistance to aminoglycosides and its potential for discovering new compounds from silent fungal metabolic pathways. This approach could be applied to elicit the metabolic potentials of other fungal isolates to discover new compounds from cryptic secondary metabolites.

Preparation and characterization of an extracellular polysaccharide produced by the deep-sea fungus Penicillium griseofulvum

The deep-sea fungus Penicillium griseofulvum produces an extracellular polysaccharide, Ps1-1, when grown in potato dextrose-agar medium. Ps1-1 was isolated from the fermented broth using ethanol precipitation, anion-exchange and size-exclusion chromatography. Ps1-1 is a galactomannan with a molecular weight of about 20kDa, and a molar ratio of mannose and glucose of 1.1:1.0. On the basis of one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR) and mass spectroscopic analyses, Ps1-1 is composed of a long chain of galactofuranan and a mannose core. The galactofuranan chain consists of (1→5)-linked β-galactofuranose, with additional branches at C-6 consisting of (1→)-linked β-galactofuranose residues and phosphate esters. The mannan core is composed of (1→6)-linked α-mannopyranose substituted at C-2 by (1→)-linked α-mannopyranose residues, disaccharide and trisaccharide units of (1→2)-linked α-mannopyranose. The investigation demonstrated that Ps1-1 was a galactofuranose-containing galactomannan differing from previously described extracellular polysaccharides.

Chemical profile of the secondary metabolites produced by a deep-sea sediment-derived fungus Penicillium commune SD-118

Bioassay-guided fractionation of the crude extract from Penicillium commune SD-118, a fungus obtained from a deep-sea sediment sample, resulted in the isolation of a known antibacterial compound, xanthocillin X (1), and 14 other known compounds comprising three steroids (2–4), two ceramides (5 and 6), six aromatic compounds (7–12), and three alkaloids (13–15). Xanthocillin X (1) was isolated for the first time from a marine fungus. In the bioassay, xanthocillin X (1) displayed remarkable antimicrobial activity against Staphylococcus aureus and Escherichia coli, and significant cytotoxicity against MCF-7, HepG2, H460, Hela, Du145, and MDA-MB-231 cell lines. Meleagrin (15) exhibited cytotoxicity against HepG2, Hela, Du145, and MDA-MB-231 cell lines. This is the first report of the cytotoxicity of xanthocillin X (1).

Ascomycete phylotypes recovered from a Gulf of Mexico methane seep are identical to an uncultured deep-sea fungal clade from the Pacific

Deep-sea endemic fungi are one component of an under-sampled invisible biosphere whose contribution to benthic ecosystems is not yet understood. In the last decade, molecular techniques have facilitated the discovery of several new deep-sea fungal groups, especially in habitats such as hydrothermal vents and methane seeps. We assessed fungal diversity at a methane seep in the Gulf of Mexico by sequencing partial ITS and LSU gene regions from environmental DNA recovered from microoxic and anoxic sediment. While most phylotypes were closely allied with common fungal species, the dominant phylotype did not match any known terrestrial species and aligned with an uncultured deep-sea fungus found in oxygen-depleted sediment at multiple sites in the Pacific Ocean. Despite its apparently broad distribution and frequent occurrence in oxygen-depleted sediment, the ecological role of this phylotype is not yet known.

New Cytotoxic Metabolites from a Deep‐Sea‐Derived Fungus, Phialocephala sp., Strain FL30r

Two new sorbicillinoids, 1 and 2, together with a novel benzofuranone derivative named phialofurone (3), were isolated from a deep-sea sediment-derived fungus, Phialocephala sp. Their structures were established on the basis of spectroscopic data. All compounds displayed cytotoxic effects against P388 (IC(50) values of 11.5±1.4, 0.1±0.1, and 0.2±0.01 μM, resp.) and K562 (IC(50) values of 22.9±0.8, 4.8±0.3 and 22.4±0.9 μM, resp.) cell lines.

Trisorbicillinone A, a Novel Sorbicillin Trimer, from a Deep Sea Fungus, Phialocephala sp. FL30r.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Two New Bisorbicillinoids Isolated from a Deep‐Sea Fungus, Phialocephala sp. FL30r.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Two new metabolites with cytotoxicities from deep-sea fungus, aspergillus sydowi YH11-2

Two new compounds, 2, 3, 5-trimethyl-6-(3-oxobutan-2-yl)-4H-pyran-4-one (1) and (2R)-2, 3- dihydro-7-hydroxy-6, 8-dimethyl-2-[(E)-prop-1-enyl] chromen-4-one (2), together with six known compounds (3-8), were isolated from a deep-sea fungus, identified as Aspergillus sydowi, by a bioassay-guided method. Their structures were elucidated by spectroscopic methods and the cytotoxicities were evaluated by SRB method.

Trisorbicillinone A, a novel sorbicillin trimer, from a deep sea fungus, Phialocephala sp. FL30r

A novel sorbicillin trimer, trisorbicillinone A ( 1), was isolated from a deep sea fungus, Phialocephala sp. FL30r. The structure and relative stereochemistry of 1 were determined based on spectroscopic methods. Trisorbicillinone A ( 1) showed cytotoxicity against P388 and HL60 cells with the IC 50 value of 9.10 and 3.14 μM, respectively.

Two New Bisorbicillinoids Isolated from a Deep-sea Fungus, Phialocephala sp. FL30r

Two new bisorbicillinoids, named oxosorbiquinol (1) and dihydrooxosorbiquinol (2), were isolated from a deep-sea fungus, Phialocephala sp., and their structures established using spectroscopic methods. The absolute configurations of 1 and 2 were determined by their biosynthesis route and analysis of the CD spectrum. Their cytotoxic effects on P388, A-549, HL60, BEL7402 and K562 cell lines were examined by the MTT method.