Summary: Fungi populate deep Oceans in extreme habitats characterized by high hydrostatic pressure, low temperature and absence of sunlight. Marine fungi are potential major contributors to biogeochemical events, critical for marine communities and food web equilibrium under climate change conditions and a valuable source of novel extremozymes and small molecules. Despite their ecophysiological and biotechnological relevance, fungal deep‐sea biodiversity has not yet been thoroughly characterized. In this study, we describe the culturable mycobiota associated with the deepest margin of the European Western Continental Shelf: sediments sampled at the Porcupine Bank and deep‐water corals and sponges sampled in the Whittard Canyon. Eighty‐seven strains were isolated, belonging to 43 taxa and mainly Ascomycota. Ten species and four genera were detected for the first time in the marine environment and a possible new species of Arachnomyces was isolated from sediments. The genera Cladosporium and Penicillium were the most frequent and detected on both substrates, followed by Candida and Emericellopsis . Our results showed two different fungal communities: sediment‐associated taxa which were predominantly saprotrophic and animal‐associated taxa which were predominantly symbiotic. This survey supports selective fungal biodiversity in the deep North Atlantic, encouraging further mycological studies on cold water coral gardens, often overexploited marine habitats.

Aims Identification of the mycobiota associated to the marine echinoderm Holothuria poli and investigation of cytotoxic and pro‐osteogenic potential of isolated strains. Methods and results Fungal strains were isolated from the animals body‐wall, intestine, and faeces. The species identification was based on DNA barcoding and morphophysiological observations. Forty‐seven species were identified, all Ascomycota and mainly belonging to Aspergillus and Penicillium genera. Sixteen strains were grown on three media for chemical extraction. Cytotoxic activity was tested on a hepatic cancer cell line (HepG2), the cells viability was evaluated after treatment using a resazurin based assay (AlamarBlue). Pro‐osteogenic activity was tested on human Mesenchymal Stem Cell, differentiation was measured as the alkaline phosphatase production through reaction with p‐nitrophenylphosphate or as the cells ability to mineralize calcium using a colorimetric kit (StanBio). Cytotoxic activity was recorded for four fungal species while five out of 48 extracts highlighted bioactivity toward human mesenchymal stem cells. Conclusions The presence of relevant animal‐associated mycobiota was observed in H. poli and selected strains showed cytotoxic potential and pro‐osteogenic activity. Significance and importance of this study Our work represents the first report of a Mediterranean sea cucumber mycobiota and highlights the isolates potential to synthetize compounds of pharmaceutical interest for regenerative medicine.

Worldwide diffused diseases such as osteoarthritis, atherosclerosis or chronic kidney disease are associated with a tissue calcification process which may involve unexpected local stem cell differentiation. Current pharmacological treatments for such musculoskeletal conditions are weakly effective, sometimes extremely expensive and often absent. The potential to develop new therapies is represented by the discovery of small molecules modulating resident progenitor cell differentiation to prevent aberrant tissue calcification. The marine environment is a rich reserve of compounds with pharmaceutical potential and many novel molecules are isolated from macro and microorganisms annually. The potential of small molecules synthetized by marine filamentous fungi to influence the osteogenic and chondrogenic differentiation of human mesenchymal stem/stromal cells (hMSCs) was investigated using a novel, high-throughput automated screening platform. Metabolites synthetized by the marine-derived fungus Penicillium antarcticum were evaluated on the platform. Itaconic acid derivatives were identified as inhibitors of calcium elaboration into the matrix of osteogenically differentiated hMSCs and also inhibited hMSC chondrogenic differentiation, highlighting their capacity to impair ectopic calcification. Bioactive small molecule discovery is critical to address ectopic tissue calcification and the use of biologically relevant assays to identify naturally occurring metabolites from marine sources represents a strategy that can contribute to this effort.

Chronic diseases characterized by bone and cartilage loss are associated with a reduced ability of progenitor cells to regenerate new tissues in an inflammatory environment. A promising strategy to treat such diseases is based on tissue repair mediated by human mesenchymal stem cells (hMSCs), but therapeutic outcomes are hindered by the absence of small molecules to efficiently modulate cell behaviour. Here, we applied a high-throughput drug screening technology to bioprospect a large library of extracts from Irish deep-sea organisms to induce hMSC differentiation toward musculoskeletal lineages and reduce inflammation of activated macrophages. The library included extracts from deep-sea corals, sponges and filamentous fungi representing a novel source of compounds for the targeted bioactivity. A validated hit rate of 3.4% was recorded from the invertebrate library, with cold water sea pens (octocoral order Pennatulacea), such as Kophobelemnon sp. and Anthoptilum sp., showing the most promising results in influencing stem cell differentiation toward osteogenic and chondrogenic lineages. Extracts obtained from deep-sea fungi showed no effects on stem cell differentiation, but a 6.8% hit rate in reducing the inflammation of activated macrophages. Our results demonstrate the potential of deep-sea organisms to synthetize pro-differentiation and immunomodulatory compounds that may represent potential drug development candidates to treat chronic musculoskeletal diseases.

Oceanic bathyal benthos harbours extremotolerant microbial species living with low nutrient availability, high hydrostatic pressure, and low temperature. Within their community, bacteria can secrete signalling molecules to gain a competitive advantage over space and nutrients, often representing bioactive compounds with relevant biotechnological potential. In this study, we investigate the species diversity of culturable bacteria associated with sediments sampled at the deepest margin of the European Western Continental Shelf. Furthermore, we explore their biosynthesis of known and new bioactive molecules. We isolated 144 bacterial strains belonging to 60 different taxa, including potentially new species, two species never recorded in the marine environment, and 15 new to the deep‐sea. Investigation of the bacteria ability to synthesise ecologically relevant molecules was performed through genetic screening and metabolomics. Our results highlight a high rate of antibiotic‐producing bacteria as well as the biosynthesis of potentially quorum‐sensing compounds. Actinobacteria displayed the highest potential to biosynthesise bioactive molecules such as polyketides and non‐ribosomal peptides, with a high rate of isolates carrying biosynthetic genes as well as the highest number of molecules detected by mass spectrometry. In this study, the deep‐sea demonstrates a valuable source of unknown microbial and chemical diversity, supporting initiatives aimed at its protection from anthropogenic disturbance.

Fungi constitute an essential component of marine biodiversity and contribute to the ecosystem functioning through their symbiotic interactions and cycling of nutrients. Marine fungi are commonly recorded in association with inert or living substrates, in environmental conditions ranging from shallow temperate waters to extreme habitats with low temperature, nutrients, light and/or oxygen. Species occurrence data are abundant and continuously growing, although often scattered across research articles in various fields and missing systematic archiving. The development of accessible databases with curated occurrence records is essential to highlight the biodiversity of marine fungi and support quantitative analysis of their functions. To this end, we assembled a new dataset consisting of records of fungi from the marine environment in the Mediterranean Sea. Literature search was performed in Google Scholar by using keywords “marine”, “fungi”, “Mediterranean”, “Sea” in English, Italian, French, Spanish, and German. We manually analysed each article to check for relevance, and listed recorded fungal taxa in our dataset. Other than occurrence data and metadata, we annotated each record for its trophic behaviour and likeliness to implement it, following the criteria of FUNTRAITS. From 130 articles we manually extracted 4630 fungal records, and classified them as primary or secondary records whether they represented new observations or reported previously published records. Most fungal taxa were obtained from samples gathered in coastal environment compared to the open sea. Samples carrying the majority of fungal records were living organisms and organic natural substrates, while a minority of records was observed on organic artificial or inorganic substrates. The identification of recorded fungi was performed in most cases to the species level, with taxa belonging to Ascomycota and Basidiomycota phyla dominating the depicted biodiversity. Our study sheds light on the currently known diversity of fungi in the Mediterranean Sea, calling for increased actions to map fungi in understudied marine environments as well as more studies delving deeper on the function of fungi in their habitat.