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Fungi are phylogenetically and functionally diverse ubiquitous components of almost all ecosystems on Earth, including aquatic environments stretching from high montane lakes down to the deep ocean. Aquatic ecosystems, however, remain frequently overlooked as fungal habitats, although fungi potentially hold important roles for organic matter cycling and food web dynamics. Recent methodological improvements have facilitated a greater appreciation of the importance of fungi in many aquatic systems, yet a conceptual framework is still missing. In this Review, we conceptualize the spatiotemporal dimensions, diversity, functions and organismic interactions of fungi in structuring aquatic food webs. We focus on currently unexplored fungal diversity, highlighting poorly understood ecosystems, including emerging artificial aquatic habitats.In this Review, Grossart and colleagues conceptualize the spatiotemporal dimensions, diversity, functions and organismic interactions of fungi in structuring aquatic food webs. They focus on currently unexplored aquatic fungal diversity, highlighting poorly understood ecosystems, including emerging artificial aquatic habitats.

Terrestrial fungi play critical roles in nutrient cycling and food webs and can shape macroorganism communities as parasites and mutualists. Although estimates for the number of fungal species on the planet range from 1.5 to over 5 million, likely fewer than 10% of fungi have been identified so far. Terrestrial fungi play critical roles in nutrient cycling and food webs and can shape macroorganism communities as parasites and mutualists. Although estimates for the number of fungal species on the planet range from 1.5 to over 5 million, likely fewer than 10% of fungi have been identified so far. To date, a relatively small percentage of described species are associated with marine environments, with ∼1,100 species retrieved exclusively from the marine environment. Nevertheless, fungi have been found in nearly every marine habitat explored, from the surface of the ocean to kilometers below ocean sediments. Fungi are hypothesized to contribute to phytoplankton population cycles and the biological carbon pump and are active in the chemistry of marine sediments. Many fungi have been identified as commensals or pathogens of marine animals (e.g., corals and sponges), plants, and algae. Despite their varied roles, remarkably little is known about the diversity of this major branch of eukaryotic life in marine ecosystems or their ecological functions. This perspective emerges from a Marine Fungi Workshop held in May 2018 at the Marine Biological Laboratory in Woods Hole, MA. We present the state of knowledge as well as the multitude of open questions regarding the diversity and function of fungi in the marine biosphere and geochemical cycles.

Here, we report about a unique aquatic fungus Mucor hiemalisEH8 that can remove toxic ionic mercury from water by intracellular accumulation and reduction into elemental mercury (Hg0). EH8 was isolated from a microbial biofilm grown in sulfidic‐reducing spring water sourced at a Marching's site located downhill from hop cultivation areas with a history of mercury use. A thorough biodiversity survey and mercury‐removal function analyses were undertaken in an area of about 200 km2 in Bavaria (Germany) to find the key biofilm and microbe for mercury removal. After a systematic search using metal removal assays we identified Marching spring's biofilm out of 18 different sulfidic springs' biofilms as the only one that was capable of removing ionic Hg from water. EH8 was selected, due to its molecular biological identification as the key microorganism of this biofilm with the capability of mercury removal, and cultivated as a pure culture on solid and in liquid media to produce germinating sporangiospores. They removed 99% of mercury from water within 10–48 h after initial exposure to Hg(II). Scanning electron microscopy demonstrated occurrence of intracellular mercury in germinating sporangiospores exposed to mercury. Not only associated with intracellular components, but mercury was also found to be released and deposited as metallic‐shiny nanospheres. Electron‐dispersive x‐ray analysis of such a nanosphere confirmed presence of mercury by the HgMα peak at 2.195 keV. Thus, a first aquatic eukaryotic microbe has been found that is able to grow even at low temperature under sulfur‐reducing conditions with promising performance in mercury removal to safeguard our environment from mercury pollution. Here, we report about a unique aquatic fungus Mucor hiemalis EH8 that can remove toxic ionic mercury from water by intracellular accumulation and reduction into elemental mercury. It removed 99% of mercury from water within 10–48 h after exposure to Hg(II). Scanning electron microscopy demonstrated occurrence of intracellular mercury in germinating sporangiospores exposed to mercury.

Most of the described species in kingdom Fungi are contained in two phyla, the Ascomycota and the Basidiomycota (subkingdom Dikarya). As a result, our understanding of the biology of the kingdom is heavily influenced by traits observed in Dikarya, such as aerial spore dispersal and life cycles dominated by mitosis of haploid nuclei. We now appreciate that Fungi comprises numerous phylum-level lineages in addition to those of Dikarya, but the phylogeny and genetic characteristics of most of these lineages are poorly understood due to limited genome sampling. Here, we addressed major evolutionary trends in the non-Dikarya fungi by phylogenomic analysis of 69 newly generated draft genome sequences of the zoosporic (flagellated) lineages of true fungi. Our phylogeny indicated five lineages of zoosporic fungi and placed Blastocladiomycota, which has an alternation of haploid and diploid generations, as branching closer to the Dikarya than to the Chytridiomyceta. Our estimates of heterozygosity based on genome sequence data indicate that the zoosporic lineages plus the Zoopagomycota are frequently characterized by diploid-dominant life cycles. We mapped additional traits, such as ancestral cell-cycle regulators, cell-membrane– and cell-wall–associated genes, and the use of the amino acid selenocysteine on the phylogeny and found that these ancestral traits that are shared with Metazoa have been subject to extensive parallel loss across zoosporic lineages. Together, our results indicate a gradual transition in the genetics and cell biology of fungi from their ancestor and caution against assuming that traits measured in Dikarya are typical of other fungal lineages.

Abstract Research on freshwater fungi has concentrated on their role in plant litter decomposition in streams. Higher fungi dominate over bacteria in terms of biomass, production and enzymatic substrate degradation. Microscopy-based studies suggest the prevalence of aquatic hyphomycetes, characterized by tetraradiate or sigmoid spores. Molecular studies have consistently demonstrated the presence of other fungal groups, whose contributions to decomposition are largely unknown. Molecular methods will allow quantification of these and other microorganisms. The ability of aquatic hyphomycetes to withstand or mitigate anthropogenic stresses is becoming increasingly important. Metal avoidance and tolerance in freshwater fungi implicate a sophisticated network of mechanisms involving external and intracellular detoxification. Examining adaptive responses under metal stress will unravel the dynamics of biochemical processes and their ecological consequences. Freshwater fungi can metabolize organic xenobiotics. For many such compounds, terrestrial fungal activity is characterized by cometabolic biotransformations involving initial attack by intracellular and extracellular oxidative enzymes, further metabolization of the primary oxidation products via conjugate formation and a considerable versatility as to the range of metabolized pollutants. The same capabilities occur in freshwater fungi. This suggests a largely ignored role of these organisms in attenuating pollutant loads in freshwaters and their potential use in environmental biotechnology.

Advancements in chemical, medical, cosmetic, and plastic producing industries have improved agricultural yields, health and human life in general. As a negative consequence, a plethora of chemicals are intentionally and unintentionally released to terrestrial and aquatic environments with sometimes devastating effects for entire ecosystems. One mitigation strategy to counteract this pollution is bioremediation. Bioremediation is an umbrella term for biologically mediated processes during which an undesired compound is transformed, degraded, sequestered and/or entirely removed from the ecosystem. Organisms across all domains of life may mediate bioremediation; yet, fungi are particularly promising candidates. They possess metabolic capabilities to break down complex molecules which make fungi the ultimate degraders of recalcitrant organic matter in nature. Bioremediation by fungi, also termed mycoremediation, has been more frequently investigated in terrestrial than aquatic ecosystems, although fungi also thrive in lacustrine and marine environments. Here, we focus on mycoremediation of emerging pollutants in aquatic environments. In this context, we draw parallels between terrestrial and aquatic fungal taxa, and their role in mycoremediation. We discuss the ability of fungi to break-down (i) pesticides, (ii) pharmaceuticals and personal care products, (iii) plastics, both conventional types and (iv) bioplastics, and fungal role, (v) mitigation of heavy metal pollution. Furthermore, we (vi) discuss possible mycoremediation strategies in applied settings and highlight novel enzyme based mycoremediation strategies.

During a survey of aero-aquatic fungi in Thailand, an undescribed helicosporous fungus was discovered. It is characterized by the presence of branched and septate hyphae with hyaline conidiophores that are micronematous or semi-macronematous, acrogenous and holoblastic. Conidia are hyaline and centrifugally coiled (excentric), helicoid or circinate, coiled 2–3 times clockwise or counterclockwise. After comparison of morphological and molecular characters with other aero-aquatic, helicosporous fungi, introduction of a new genus and species is proposed, Helicocentralis hyalina gen. et sp. nov. Phylogenetic analyses based on the combined sequence data from the small and large nuclear subunit ribosomal DNA (SSU and LSU), as well as internal transcribed spacer (ITS) rDNA sequence data, the fungus groups within the Leotiomycetes class with strong statistical support. The new genus is not related to other helicosporous hyphomycete genera ( Helicoma , Helicomyces , Helicoön , and Helicosporium ), which belong in the Tubeufiaceae, Dothideomycetes. Within the Leotiomycetes, our new fungus is distantly related to Helicodendron paradoxum (the type species). The new fungus is also compared morphologically to six similar helicosporous genera from Dothideomycetes and Leotiomycetes.

Hypocreomycetidae is a highly diverse group with species from various habitats. This subclass has been reported as pathogenic, endophytic, parasitic, saprobic, fungicolous, lichenicolous, algicolous, coprophilous and insect fungi from aquatic and terrestrial habitats. In this study, we focused on freshwater fungi of Hypocreomycetidae which resulted 41 fresh collections from China and Thailand. Based on morphological and phylogenetic analyses, we identified 26 species that belong to two orders ( Hypocreales and Microascales ) and six families ( Bionectriaceae , Halosphaeriaceae , Microascaceae , Nectriaceae , Sarocladiaceae and Stachybotryaceae ). Ten new species are introduced and 13 new habitats and geographic records are reported. Mariannaea superimposita, Stachybotrys chartarum and S. chlorohalonatus are recollected from freshwater habitats in China. Based on phylogenetic analysis of combined LSU, ITS, SSU, rpb 2 and tef 1-α sequences data, Emericellopsis is transferred to Hypocreales genera incertae sedis ; Pseudoacremonium is transferred to Bionectriaceae ; Sedecimiella is placed in Nectriaceae ; Nautosphaeria and Tubakiella are excluded from Halosphaeriaceae and placed in Microascales genera incertae sedis ; and Faurelina is excluded from Hypocreomycetidae . Varicosporella is placed under Atractium as a synonym of Atractium . In addition, phylogenetic analysis and divergence time estimates showed that Ascocodina , Campylospora , Cornuvesica and Xenodactylariaceae form distinct lineages in Hypocreomycetidae and they evolved in the family/order time frame. Hence, a new order ( Xenodactylariales ) and three new families ( Ascocodinaceae , Campylosporaceae and Cornuvesicaceae ) are introduced based on phylogenetic analysis, divergence time estimations and morphological characters. Ancestral character state analysis is performed for different habitats of Hypocreomycetidae including freshwater, marine and terrestrial taxa. The result indicates that marine and freshwater fungi evolved independently from terrestrial ancestors. The results further support those early diverging clades of this subclass, mostly comprising terrestrial taxa and freshwater and marine taxa have been secondarily derived, while the crown clade ( Nectriaceae ) is represented in all three habitats. The evolution of various morphological adaptations towards their habitual changes are also discussed.

The outburst of microbial resistance to antibiotics creates the need for new sources of active compounds for the treatment of pathogenic microorganisms. Marine microalgae are of particular interest in this context because they have developed tolerance and defense strategies to resist the exposure to pathogenic bacteria, viruses, and fungi in the aquatic environment. Although antimicrobial activities have been reported for some microalgae, natural algal bioactive peptides have not been described yet. In this work, acid extracts from the microalga Tetraselmis suecica with antibacterial activity were analyzed, and de novo sequences of peptides were determined. Synthetic peptides and their alanine and lysine analogs allowed identifying key residues and increasing their antibacterial activity. Additionally, it was determined that the localization of positive charges within the peptide sequence influences the secondary structure with tendency to form an alpha helical structure.

During a north–south latitudinal survey of aquatic fungi on submerged wood and herbaceous material in streams in the Asian region, we collected several hyphomycetous taxa. This paper is part of a series where we provide illustrated accounts of these taxa and place them in a natural classification in the fungi. DNA sequence based phylogenies in recent literature have shown that Dendryphion , Sporidesmium and Torula-like species are polyphyletic in the phylum Ascomycota and their taxonomyhas been problematic due to a lack of understanding of the importance of morphological characters used to delimit taxa, as well as the lack of ex-type or reference strains. Based on multi-locus phylogenies together with morphology, we propose the novel family Distoseptisporaceae (Sordariomycetes) and three novel genera Neotorula ( Pleosporales , Dothideomycetes), Distoseptispora (Sordariomycetes) and Pseudosporidesmium (Sordariomycetes). In addition, Dendryphion aquaticum , D. submersum , Distoseptispora fluminicola , D. aquatica , Kirschsteiniothelia submersa , Neotorula aquatica , Sporidesmium aquaticum , S. submersum and S. fluminicola are introduced as new species. Pseudosporidesmium knawiae comb. nov . is proposed to accommodate Sporidesmium knawiae in Sordariomycetes. The polyphyletic nature of Dendryphion , Sporidesmium and Torula-like species are partially resolved, but further sampling with fresh collections and molecular data of species are needed to obtain a natural classification.