Fungal Biodiversity in Salt Marsh Ecosystems

A New Genus of the Microascaceae (Ascomycota) Family from a Hypersaline Lagoon in Spain and the Delimitation of the Genus Wardomyces

The Saladas de Sástago-Bujaraloz is an endorheic and arheic complex of lagoons located in the Ebro Basin and protected by the Ramsar Convention on Wetlands. Due to the semi-arid climate of the region and the high salinity of their waters, these lagoons constitute an extreme environment. We surveyed the biodiversity of salt-tolerant and halophilic fungi residents of the Laguna de Pito, a lagoon belonging to this complex. Therefore, we collected several samples of water, sediments, and soil of the periphery. Throughout the study, we isolated 21 fungal species, including a strain morphologically related to the family Microascaceae. However, this strain did not morphologically match any of genera within this family. After an in-depth morphological characterization and phylogenetic analysis using a concatenated sequence dataset of four phylogenetically informative molecular markers (the internal transcribed spacer region (ITS) of the nuclear ribosomal DNA (nrDNA); the D1-D2 domains of the 28S gene of the nuclear ribosomal RNA (LSU); and a fragment of the translation elongation factor 1-alpha (EF-1α) and the β-tubulin (tub2) genes), we established the new genus Dactyliodendromyces, with Dactyliodendromyces holomorphus as its species. Additionally, as a result of our taxonomic study, we reclassified the paraphyletic genus Wardomyces into three different genera: Wardomyces sensu stricto, Parawardomyces gen. nov., and Pseudowardomyces gen. nov., with Parawardomyces ovalis (formerly Wardomyces ovalis) and Pseudowardomyces humicola (formerly Wardomyces humicola) as the type species of their respective genera. Furthermore, we propose new combinations, including Parawardomyces giganteus (formerly Wardomyces giganteus) and Pseudowardomyces pulvinatus (formerly Wardomyces pulvinatus).

Succession of Fungal Communities and Their Functional Profiles in a Decaying Foundation Species

Dead plant biomass from foundation plant species is fundamental for the survival of coastal salt marshes because dead biomass aids in the vertical accretion of the ecosystem. Fungi regulate the decomposition of dead biomass, and thus play an essential role for marsh survival. Despite their importance, little is known about the compositional and functional changes of fungal communities in plant matter throughout senescence and litter decomposition. Here, we analyzed how fungal communities and their functionality change in the foundation plant species Spartina patens, which builds vast amounts of dead plant biomass (thatch) on the soil surface. We analyzed the chemical and fungal properties of live biomass, standing dead biomass (dead biomass shortly after senescence), upper thatch (top layer of litter on the soil surface), and lower thatch (bottom layer of litter on the soil surface) during September and November of 2021. We found that the chemical and fungal properties of different S. patens biomass types followed a predictable litter decomposition pattern. Notably, live biomass, standing dead biomass, upper thatch, and lower thatch all hosted unique fungal communities and litter chemistry. Functional groups present in live biomass (pathogens, epiphytes, and mycoparasites) were lost during senescence and later replaced by diverse saprotrophs. The abundance of lignocellulose saprotrophs increased throughout decomposition, with the highest abundance occurring in lower thatch. These results suggest a predictable succession of fungal communities through the senescence and decomposition of the foundation species S. patens. Our study highlights the diversity of fungal communities in a disappearing foundation species.

Seasonal and Spatial Dynamics of Fungal Diversity and Communities in the Intertidal Zones of Qingdao, China

Intertidal zones comprise diverse habitats and directly suffer from the influences of human activities. Nevertheless, the seasonal fluctuations in fungal diversity and community structure in these areas are not well comprehended. To address this gap, samples of seawater and sediment were collected seasonally from the estuary and swimming beaches of Qingdao's intertidal areas in China and were analyzed using a metabarcoding approach targeting ITS2 rDNA regions. Compared to the seawater community dominated by Ciliophora and Agaricomycetes, the sediment community was rather dominated by Dothideomycetes and Eurotiomycetes. Furthermore, the seawater community shifted with the seasons but not with the locations, while the sediment community shifted seasonally and spatially, with a specific trend showing that Cladosporium, Alternaria, and Aureobasidium occurred predominantly in the estuarine habitats during winter and in the beach habitats during spring. These spatiotemporal shifts in fungal communities' composition were supported by the PERMANOVA test and could be explained partially by the environmental variables checked, including temperature, salinity, and total organic carbon. Unexpectedly, the lowest fungal richness was observed in the summer sediments from two swimming beaches which were attracting a high influx of tourists during summer, leading to a significant anthropogenic influence. Predicted trophic modes of fungal taxa exhibited a seasonal pattern with an abundance of saprotrophic fungi in the summer sediments, positively correlating to the temperature, while the taxa affiliated with symbiotroph and pathotroph-saprotroph occurred abundantly in the winter and spring sediments, respectively. Our results demonstrate the space-time shifts in terms of the fungal community, as well as the trophic modes in the intertidal region, providing in-depth insights into the potential influence of environmental factors and human activity on intertidal mycobiomes.

Comparative analysis of antimicrobial compounds from endophytic Buergenerula spartinae from orchid

A rare fungal endophyte, identified as Buergenerula spartinae (C28), was isolated from the roots of Cymbidium orchids and was characterised and evaluated for its antimicrobial activities. Bio-guided fractionation revealed 4 fractions from B. spartinae (C28) having antibacterial activities against at least one bacterial pathogen tested (Bacillus cereus and Staphylococcus aureus). However, inhibitory activities were absent against pathogenic fungi (Ganoderma boninense, Pythium ultimum and Fusarium solani). Fraction 2 and fraction 4 of B. spartinae (C28) exhibited potent antibacterial activities against S. aureus (MIC: 0.078 mg/mL) and B. cereus (MIC: 0.313 mg/mL), respectively. LCMS analysis revealed the presence of antibacterial agents and antibiotics in fraction 2 (benoxinate, pyropheophorbide A, (-)-ormosanine and N-undecylbenzenesulfonic acid) and fraction 4 (kaempferol 3-p-coumarate, 6-methoxy naphthalene acetic acid, levofuraltadone, hinokitiol glucoside, 3-α(S)-strictosidine, pyropheophorbide A, 5'-hydroxystreptomycin, kanzonol N and 3-butylidene-7-hydroxyphthalide), which may be responsible for the antibacterial activities observed. Most of the bioactive compounds profiled from the antibacterial fractions were discovered for the first time from endophytic isolates (i.e. from B. spartinae (C28)). Buergenerula spartinae (C28) from Cymbidium sp. is therefore, an untapped resource of bioactive compounds for potential applications in healthcare and commercial industries.

Diversity and Dynamics of Marine Arenicolous Fungi in Three Seasides of the Korean Peninsula

Various arenicolous fungal species have been detected from the beach sand in the coastal area. However, little has been revealed regarding their distribution and dynamics. To investigate the overall diversity of marine arenicolous fungi (MAFs) in Korea and whether the composition of MAFs is affected by ocean currents, we isolated and analyzed the fungal community from the western, southern, and eastern seasides of the Korean Peninsula. In total, 603 strains were isolated and identified as 259 species based on appropriate molecular markers for each genus (ITS, BenA, CaM, tef1, and act). The composition of MAFs showed differences among the seasides. Our results indicate that many MAFs inhabit the beach sand on the Korean Peninsula, and the composition of MAFs is also affected by ocean currents flowing along each coast.

Screening of Insecticidal and Antifungal Activities of the Culturable Fungi Isolated from the Intertidal Zones of Qingdao, China

Numerous studies focused on drug discovery perspective have proved the great potential for exploration of marine-derived fungi to seek bioactive chemicals. Yet, marine-derived fungi are less explored compared to their terrestrial counterparts. Here, 181 fungal strains (134 species) isolated from marine algae and sediment in Chinese intertidal zones were screened to reveal bioactivities using brine shrimp, green peach aphid and plant pathogens as targets. Fermentation supernatants of 85 fungal strains exhibited a high lethality (>70%) of brine shrimp at 24 h, and 14 strains appeared to be acute-toxic as featured by more than 75% mortality at 4 h, indicating efficient insecticidal bioactivity. The crude extracts of 34 strains displayed high toxicity to green peach aphid with more than 70% of mortality at 48 h. For the plant pathogens tested, the inhibitory rates of eight fungal strains affiliated with Alternaria (AS3, AS4), Amphichorda (AS7), Aspergillus (AS14), Chaetomium (AS21), Penicillium (AS46), Purpureocillium (AS55) and Trichoderma (AS67) were equal or higher than that of the positive Prochloraz, and five of them (AS7, AS14, AS21, AS55, AS67) were also strongly toxic to brine shrimp or aphid. Our findings indicate broad potential for exploration of marine-derived fungi as candidate resources to pursue bioactive compounds in controlling agricultural pests and pathogens.

Ecological and Oceanographic Perspectives in Future Marine Fungal Taxonomy

Marine fungi are an ecological rather than a taxonomic group that has been widely researched. Significant progress has been made in documenting their phylogeny, biodiversity, ultrastructure, ecology, physiology, and capacity for degradation of lignocellulosic compounds. This review (concept paper) summarizes the current knowledge of marine fungal diversity and provides an integrated and comprehensive view of their ecological roles in the world's oceans. Novel terms for 'semi marine fungi' and 'marine fungi' are proposed based on the existence of fungi in various oceanic environments. The major maritime currents and upwelling that affect species diversity are discussed. This paper also forecasts under-explored regions with a greater diversity of marine taxa based on oceanic currents. The prospects for marine and semi-marine mycology are highlighted, notably, technological developments in culture-independent sequencing approaches for strengthening our present understanding of marine fungi's ecological roles.

How Do Fungi Survive in the Sea and Respond to Climate Change?

With the over 2000 marine fungi and fungal-like organisms documented so far, some have adapted fully to life in the sea, while some have the ability to tolerate environmental conditions in the marine milieu. These organisms have evolved various mechanisms for growth in the marine environment, especially against salinity gradients. This review highlights the response of marine fungi, fungal-like organisms and terrestrial fungi (for comparison) towards salinity variations in terms of their growth, spore germination, sporulation, physiology, and genetic adaptability. Marine, freshwater and terrestrial fungi and fungal-like organisms vary greatly in their response to salinity. Generally, terrestrial and freshwater fungi grow, germinate and sporulate better at lower salinities, while marine fungi do so over a wide range of salinities. Zoosporic fungal-like organisms are more sensitive to salinity than true fungi, especially Ascomycota and Basidiomycota. Labyrinthulomycota and marine Oomycota are more salinity tolerant than saprolegniaceous organisms in terms of growth and reproduction. Wide adaptability to saline conditions in marine or marine-related habitats requires mechanisms for maintaining accumulation of ions in the vacuoles, the exclusion of high levels of sodium chloride, the maintenance of turgor in the mycelium, optimal growth at alkaline pH, a broad temperature growth range from polar to tropical waters, and growth at depths and often under anoxic conditions, and these properties may allow marine fungi to positively respond to the challenges that climate change will bring. Other related topics will also be discussed in this article, such as the effect of salinity on secondary metabolite production by marine fungi, their evolution in the sea, and marine endophytes.

Spatial and temporal variations in salt marsh microorganisms of the Wadden Sea

Salt marshes exist at the interface of the marine and the terrestrial system. Shore height differences and associated variations in inundation frequency result in altered abiotic conditions, plant communities, and resource input into the belowground system. These factors result in three unique zones, the upper salt marsh (USM), the lower salt marsh (LSM), and the pioneer zone (PZ). Marine detritus, such as micro- and macroalgae, is typically flushed into the PZ daily, with storm surges moving both salt marsh detritus and marine detritus into higher salt marsh zones. Microbial assemblages are essential for the decomposition of organic matter and have been shown to sensitively respond to changes in abiotic conditions such as oxygen supply and salinity. However, temporal and spatial dynamics of microbial communities of Wadden Sea salt marshes received little attention. We investigated the dynamics of soil microbial communities across horizontal (USM, LSM, and PZ), vertical (0-5 and 5-10-cm sediment depth), and temporal (spring, summer, and autumn) scales in the Wadden Sea salt marsh of the European North Atlantic coast using phospholipid fatty acid (PLFA) analysis. Our results show strong spatial dynamics both among salt marsh zones and between sediment depths, but temporal dynamics to be only minor. Despite varying in space and time, PLFA markers indicated that bacteria generally were the dominant microbial group across salt marsh zones and seasons, however, their dominance was most pronounced in the USM, whereas fungal biomass peaked in the LSM and algal biomass in the PZ. Only algal markers and the stress marker monounsaturated to saturated fatty acid ratio responded to seasonality. Overall, therefore, the results indicate remarkable temporal stability of salt marsh microbial communities despite strong variability in abiotic factors.

Biological and Agronomic Traits of the Main Halophytes Widespread in the Mediterranean Region as Potential New Vegetable Crops

Salinity is one of the oldest and most serious environmental problems in the world. The increasingly widespread salinization of soils and water resources represents a growing threat to agriculture around the world. A strategy to cope with this problem is to cultivate salt-tolerant crops and, therefore, it is necessary to identify plant species that are naturally adapted to high-salinity conditions. In this review, we focus our attention on some plant species that can be considered among the most representative halophytes of the Mediterranean region; they can be potential resources, such as new or relatively new vegetable crops, to produce raw or minimally processed (or ready-to-eat) products, considering their nutritional properties and nutraceuticals. The main biological and agronomic characteristics of these species and the potential health risks due to mycotoxigenic fungi have been analyzed and summarized in a dedicated section. The objective of this review is to illustrate the main biological and agronomical characteristics of the most common halophytic species in the Mediterranean area, which could expand the range of leafy vegetables on the market.