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Twelve new [11]-chaetoglobosins, chaetopseudeurins A-L (1-12), were identified from the fermentation of the endophytic fungus Pseudeurotium bakeri P1-1-1. Their structures with absolute configurations were elucidated by detailed interpretation of NMR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction. Compounds 2 and 5-7 exhibited significant cytotoxicities against seven human cancer cell lines, with IC50 values ranging from 4.7 ± 1.0 to 12.2 ± 0.7 μM, and induced G2/M cell cycle arrest and apoptosis in MCF-7 and A427 cells dose dependently. Western blot analysis showed that compound 2 induced apoptosis of MCF-7 cells via the Bcl-2/caspase-3/PARP pathway.

Six rearranged [11]-chaetoglobosins (1–6) were isolated from an endophytic fungus Pseudeurotium bakeri P1-1-1. Pseudeurglobosin A (1) possesses a rare 5/6/5/4/6-fused pentacyclic ring system. Pseudeurglobosin B (2) has a C-14–O–C-18 bridged pentacyclic 5/6/6/5/6 core. Pseudeurglobosins C–E (3–5) represent the first examples of [11]-chaetoglobosins featuring a 5/6/6/7/5 ring system. Pseudeurglobosin F (6) features a unique 5/6/6 core. Compound 1 exhibited potent immunosuppressive activity against concanavalin A-induced T cell proliferation and lipopolysaccharide-induced B cell proliferation with IC50 values of 6.0 ± 0.9 and 10.8 ± 0.3 μM, respectively. Further studies revealed that 1 induced apoptosis and inhibited cytokine secretion in activated T cells through the JAK2/PI3 K/Akt signaling pathway.

In numerous studies, researchers have explored the interactions between fungi and their hosting biota in terrestrial systems, while much less attention has been paid to the counterpart interactions in aquatic, and particularly marine, ecosystems. Despite the growing recognition of the potential functions of fungi in structuring phytoplankton communities, the current insights were mostly derived from phytoplankton hosts, such as diatoms, green microalgae, and cyanobacteria. Dinoflagellates are the second most abundant group of phytoplankton in coastal marine ecosystems, and they are notorious for causing harmful algal blooms (HABs). In this study, we used high-throughput amplicon sequencing to capture global snapshots of specific fungal assemblages associated with laboratory-cultured marine dinoflagellate. We investigated a total of 13 clonal cultures of the dinoflagellate Karlodinium veneficum that were previously isolated from 5 geographic origins and have been maintained in our laboratory from several months to more than 14 years. The total recovered fungal microbiome, which consisted of 349 ASVs (amplicon sequencing variants, sequences clustered at a 100% sequence identity), could be assigned to 4 phyla, 18 classes, 37 orders, 65 families, 97 genera, and 131 species. The fungal consortium displayed high diversity and was dominated by filamentous fungi and ascomycetous and basidiomycetous yeasts. A core set of three genera among all the detected fungi was constitutively present in the K. veneficum strains isolated from geographically distant regions, with the top two most abundant genera, Thyridium and Pseudeurotium, capable of using hydrocarbons as the sole or major source of carbon and energy. In addition, fungal taxa previously documented as endophytes in other hosts were also found in all tested strains of K. veneficum. Because host–endophyte interactions are highly variable and strongly case-dependent, these fungal taxa were not necessarily genuine endosymbionts of K. veneficum; instead, it raised the possibility that dinoflagellates could potentially serve as an alternative ecological niche for the colonization of fungal endophytes. Our findings lay the foundation for further investigations into the potential roles or functions of fungi in the regulation of the growth dynamics and HABs of marine dinoflagellates in the field.

Air sampling in the ‘Heroic Era’ historic huts on Ross Island, Antarctica confirmed fungal presence, viability and winter survival. Cultivation and consensus sequence-based identification of Cladosporium cladosporioides, Pseudeurotium desertorum, Geomyces sp. and Antarctomyces psychrotrophicus demonstrated that they dominated the air environment within the huts. Cadophora sp. and Thebolus sp. were also isolated from the air and identified by morphological characteristics. Viable fungal colony forming units generally dropped in winter 2007 samplings from levels recorded in summer 2006 but were still substantial and greater than observed in summer 2008 and summer 2009 sampling at some locations. Comparing interior to exterior sampling, at the Hut Point and Cape Evans sites, there were more fungi recovered from the air in the interiors but at Cape Royds location, more fungi were recovered from the outside environment, possibly due to the impact of large amounts of organic material from the nearby Adelie penguin rookery. This research reveals airborne fungal biodiversity in summer and winter and demonstrates spores are widespread particularly in the interiors of the huts. Completed conservation efforts appear to have reduced fungal blooms and spores, which should reduce future adverse impacts to wood, textiles, paper and other artefacts so that this important polar heritage can be preserved.

A new general concept for the total synthesis of pseurotin A (1), a secondary metabolite of Pseudeurotium ovalis STOLK, which possesses a highly substituted 1-oxa-7-azaspiro[4.4]nonane skeleton, is presented. A key intermediate of the planned reaction sequence is the functionalized γ-lactone 8. The corresponding protected compound 52 was prepared using (S)-O,O-isopropylideneglyceraldehyde (13) and the bromoacetal 14 as starting material. γ-Lactone 52 was obtained in enantiomerically pure state in ten steps. It possesses the desired configuration.

The synthesis of 2,2-bis(hydroxymethyl)-4-methyl-5-phenylfuran-3(2H)-one (9), 5-[(1S,2S,Z)-1,2-(ethylidenedioxy)hex-3-enyl]-2,2-bis(hydroxymethyl)-4-methylfuran-3(2H)-one (24), and 5-[(1S,2S,Z)-1,2-(ethylidenedioxy)hex-3-enyl]-2-(hydroxymethyl)-4-methylfuran-3(2H)-one (28), which represent more advanced, suitably functionalized intermediates for the synthesis of pseurotin A (1), a secondary metabolite of Pseudeurotium ovalis STOLK, is described.

A hyphomycetous fungus isolated from montane fen soil in the Caucasus Mountains, Russia, had obscurely sympodial conidiogenous cells that suggested a link to the heterogeneous genus Leptodontidium. Sequence analysis of the nuclear ribosomal small subunit and internal transcribed spacer region, however, disclosed that the fungus was an anamorphic member of a clade containing the cleistothecial ascomycetous genus Pseudeurotium. Teberdinia, gen. nov., is proposed for the blastic, generally sympodially proliferating anamorphs in this group, and Teberdinia hygrophila, sp. nov., is proposed for the species from upland fens. Binomials are not proposed for the remaining Teberdinia anamorphs of Pseudeurotium species. Purely anamorphic isolates in this clade are difficult to recognize using current morphological keys and might be more widely distributed and ecologically significant than is currently evident.

The structures 2–5 are assigned to the pseurotin B, C, D and E, which are new metabolites of Pseudeutorium ovalis STOLK, based on spectroscopic data and chemical transformations.

The structure and absolute configuration of pseurotin A, a new metabolite, isolated from culture filtrates of Pseudeurotium ovalis STOLK(Ascomycetes) has been shown to be (1′S, 2′S, 5S, 8S, 9R, 3′Z)-8-benzoyl-2 (1′,2-dihydroxy-3′-hexenyl)-9-hydroxy-8-methoxy-3-methyl-1-oxa-7-azaspiro [4,4]non-2-ene-4,6-dione (1).

The structure and absolute configuration of pseurotin (1), a new metabolite, isolated from culture filtrates of Pseudeurotium ovalis STOLK (Ascomycetes), has been shown to be 2-[1′(S), 2′ (S)-dihydroxhex-3′-ene-yl]-3-methyl-8(S)-methoxy-8-benzoyl-9(R)-hydroxy-(5S)-1-oxa-7-aza-spiro[4.4]non-2-ene-4, 6-dione (1), by spectral data and chemical transformations, and by X-ray analysis of its dibromo derivative 2 [1].

Feeding of [12, 13-13C]-β-trans-bergamotene to cultures of Pseudeurotium ovalis resulted in labeling of C-12 and C-13 of the antibiotic ovalicin, as established by 13 C NMR.

The structure of ovalicin, a metabolite of the fungus Pseudeurotium ovalis with immunosuppressive activity, has been determined to be 11.

The structure of ovalicine, a metabolite of the fungus Pseudeurotium ovalis with immunosuppressive activity, has been determined to be 15.

The structures 2–5 are assigned to the pseurotin B, C, D and E, which are new metabolites of Pseudeutorium ovalis STOLK, based on spectroscopic data and chemical transformations.

The structure and absolute configuration of pseurotin A, a new metabolite, isolated from culture filtrates of Pseudeurotium ovalis STOLK(Ascomycetes) has been shown to be (1′S, 2′S, 5S, 8S, 9R, 3′Z)-8-benzoyl-2 (1′,2-dihydroxy-3′-hexenyl)-9-hydroxy-8-methoxy-3-methyl-1-oxa-7-azaspiro [4,4]non-2-ene-4,6-dione (1).