Metabarcoding on both environmental DNA and RNA highlights differences between fungal communities sampled in different habitats

Benthic foraminiferal community structure and its response to heavy metals revealed using environmental DNA/RNA metabarcoding in Yueqing Bay, East China Sea

Foraminifera are among the most important components of benthic communities widely used as indicators of marine environmental changes. Determining the effect of heavy metal pollution on benthic foraminifera is a key requirement for evaluating the health of coastal ecosystems. In this study, environmental DNA (eDNA) and RNA (eRNA) metabarcoding was used to evaluate the benthic foraminiferal community structure and diversity in Yueqing Bay, East China Sea. A total of 45 genera were identified, of which Operculina was predominant. eDNA metabarcoding revealed higher species richness and molecular diversity than did eRNA, with higher values being recorded in the Oujiang Estuary and outer bay than in the inner and central bays. Exploring the relationship between the benthic foraminiferal community and heavy metals showed that Cu was a key factor affecting structure and diversity at the eRNA level. Findings suggest that Nummulites, Ammonia, and Haynesina may be sensitive to Cu pollution, while Parasorites may be tolerant to Zn and Pb.

Integrative Analysis of Nontargeted LC-HRMS and High-Throughput Metabarcoding Data for Aquatic Environmental Studies Using Combined Multivariate Statistical Approaches

Significant progress in high-throughput analytical techniques has paved the way for novel approaches to integrating data sets from different compartments. This study leverages nontarget screening (NTS) via liquid chromatography-high-resolution mass spectrometry (LC-HRMS), a crucial technique for analyzing organic micropollutants and their transformation products, in combination with biological indicators. We propose a combined multivariate data processing framework that integrates LC-HRMS-based NTS data with other high-throughput data sets, exemplified here by 18S V9 rRNA and full-length 16S rRNA gene metabarcoding data sets. The power of data fusion is demonstrated by systematically evaluating the impact of treated wastewater (TWW) over time on an aquatic ecosystem through a controlled mesocosm experiment. Highly compressed NTS data were compiled through the implementation of the region of interest-multivariate curve resolution-alternating least-squares (MCR-ALS) method, known as ROIMCR. By integrating ANOVA-simultaneous component analysis with structural learning and integrative decomposition (SLIDE), the innovative SLIDE-ASCA approach enables the decomposition of global and partial common, as well as distinct variation sources arising from experimental factors and their possible interactions. SLIDE-ASCA results indicate that temporal variability explains a much larger portion of the variance (74.6%) than the treatment effect, with both contributing to global shared space variation (41%). Design structure benefits include enhanced interpretability, improved detection of key features, and a more accurate representation of complex interactions between chemical and biological data. This approach offers a greater understanding of the natural and wastewater-influenced temporal patterns for each data source, as well as reveals associations between chemical and biological markers in an exemplified perturbed aquatic ecosystem.

The Promise of Environmental RNA Research Beyond mRNA

Environmental RNA (eRNA) studies have primarily focused on species detection and community composition through metabarcoding or metatranscriptomics, and on gene expression through messenger RNA (mRNA) abundance analysis. While valuable, this focus overlooks the broader functional roles of other RNA types in cellular metabolism. Beyond mRNA, noncoding RNAs as well as structural RNAs play critical roles in gene regulation during stress responses, development and adaptation. Additionally, RNA processes like RNA methylation or alternative splicing also respond to similar environmental or developmental signals. When applied to eRNA research, these additional RNA types and RNA processes hold significant potential as powerful, noninvasive tools for monitoring the physiological state of entire species communities. In this roadmap, we present underexplored RNA types and processes relevant for eRNA research, outlining their functions and the challenges of integrating them into the field. Expanding eRNA research to include more diverse aspects of RNA biology will require improved experimental techniques for sensitive and reliable detection and quantification of specific RNAs in eRNA samples, along with enhanced tools for taxonomic and functional annotation and the expansion of genetic reference databases. Where species-level resolution is not possible, functional inferences could be drawn at higher taxonomic levels. Expanding the scope of eRNA studies to encompass more diverse RNA types and RNA processes will provide additional insights into species communities' state, their adaptation potential and responses to stressors in a noninvasive way.

Environmental concentrations of the fungicide tebuconazole alter microbial biodiversity and trigger biofilm-released transformation products

Freshwater microbial communities are integral components of riverine biodiversity. The ecological effects of toxic chemical pollutants, such as fungicides (e.g., tebuconazole), on microbial abundance and diversity are needed for risk assessment and regulation. The emergence of RNA metabarcoding approaches allow us to describe at unprecedented resolution the microbial diversity of the active part of a microbial community. Our study assesses the ecotoxicological impact of chronic and acute tebuconazole exposures on fungal, bacterial, and algal biomass and biodiversity of aquatic fungi and bacteria in stream biofilms using an RNA metabarcoding approach. In addition, the study uses HPLC-MS to evaluate the capability of biofilms to metabolize tebuconazole. Natural biofilm communities from a Swedish stream were exposed chronically (24 days) and acutely (96 h) to environmental concentrations of tebuconazole (10 and 100 μg/L) in microcosms conditions. The diversity and community structure of fungi and bacteria was assessed by ITS2 and 16S cDNA amplicon-sequencing, respectively. Biofilms chronically exposed to tebuconazole produced and released unidentified transformation products into the water column, suggesting a biotransformation capability following 24 days of uninterrupted exposure. The fungal biomass markedly decreased by a biomass loss of 40% when chronically exposed to 10 μg/L, and 60% when chronically exposed to 100 μg/L. Bacterial and algal biomass remained comparable with the controls in all tebuconazole treatments. Fungal and bacterial alpha diversity metrics were not significantly impacted, although a decreasing trend in fungal richness was observed with the treatments. However, beta diversity was significantly impacted in both fungal and bacterial compartments. Chronic exposures resulted in a shift in community composition, where taxa potentially more tolerant to tebuconazole (i.e. Lecanoromycetes) replaced more sensitive taxa (i.e. Malasseziomycetes). This study indicates that tebuconazole at environmental concentrations might pose a risk to freshwater systems, mainly due to its high toxicity to fungi.

Evaluation of the persistence of Epichloë endophyte and its possible effect on fungal assemblages in dead leaf sheaths

The systemic fungal endophytes of the genus Epichloë inhabit the aerial part of host grasses. Recent studies have reported that Epichloë affects the non-systemic endophytic assemblages in live leaves, but few studies that have demonstrated the occurrence of Epichloë and its effect on fungal assemblages in dead leaves. We proposed a hypothesis that Epichloë decreases from live to dead leaves but affects the non-systemic endophytic assemblages also in dead leaves. To test this hypothesis, we sampled leaf sheaths from four leaf types (live, senescent, attached dead and fallen dead) of two native grass species Elymus racemifer and Elymus tsukushiensis var. transiens in Japan and assessed for fungi by DNA metabarcoding. The occurrence of Epichloë OTU was significantly greater in E. tsukushiensis var. transiens than in E. racemifer and varied significantly between the four-leaf types, with decreased and no detections in attached dead and fallen dead leaves, respectively. The composition of non-systemic endophytic assemblages was also significantly affected by the presence/absence of Epichloë OTU, leaf type, host grass species and their interactions. These results supported our hypothesis and suggested that Epichloë can indirectly lead to the changes in belowground processes such as litter decomposition by affecting saprotrophic fungi in dead leaves.

Vulnerability of Arctic Ocean microbial eukaryotes to sea ice loss

The Arctic Ocean (AO) is changing at an unprecedented rate, with ongoing sea ice loss, warming and freshening impacting the extent and duration of primary productivity over summer months. Surface microbial eukaryotes are vulnerable to such changes, but basic knowledge of the spatial variability of surface communities is limited. Here, we sampled microbial eukaryotes in surface waters of the Beaufort Sea from four contrasting environments: the Canada Basin (open ocean), the Mackenzie Trough (river-influenced), the Nuvuk region (coastal) and the under-ice system of the Canada Basin. Microbial community structure and composition varied significantly among the systems, with the most phylogenetically diverse communities being found in the more coastal systems. Further analysis of environmental factors showed potential vulnerability to change in the most specialised community, which was found in the samples taken in water immediately beneath the sea ice, and where the community was distinguished by rare species. In the context of ongoing sea ice loss, specialised ice-associated microbial assemblages may transition towards more generalist assemblages, with implications for the eventual loss of biodiversity and associated ecosystem function in the Arctic Ocean.

Diversity and Distribution of Fungal Infections in Rwanda: High Risk and Gaps in Knowledge, Policy, and Interventions

Fungal infections (FIs) are spreading globally, raising a significant public health concern. However, its documentation remains sparse in Africa, particularly in Rwanda. This report provides a comprehensive review of FIs in Rwanda based on a systematic review of reports published between 1972 and 2022. The findings reveal a rich diversity of fungal pathogens, including Blastomyces, Candida, Cryptococcus, Histoplasma, Microsporum, Pneumocystis, Rhinosporidium, and Trichophyton caused human infections. Candida infections predominantly affect the vagina mucosa, while Histoplasma duboisi was linked to disseminated infections. Other pathogens, such as Blastomyces dermatitidis and Rhinosporidium seeberi, were associated with cerebellar and nasal mucosa infections, respectively. The widespread observation of soilborne fungi affecting bean crops highlights the pathogens' threat to agricultural productivity, food security, and socioeconomic stability, as well as potential health impacts on humans, animals, and the environment. Of particular importance is that there is no information about FIs among animals in the country. Moreover, the analysis underscores significant limitations in the detection, reporting, and healthcare services related to FIs in the country, indicating gaps in diagnostic capacity and surveillance systems. This is underscored by the predominant use of traditional diagnostic techniques, including culture, cytology, and histopathology in the absence of integrating more sensitive and specific molecular tools in investigating FIs. Developing the diagnostic capacities and national surveillance systems are urgently needed to improve the health of crops, animals, and humans, as well as food security and socioeconomic stability in Rwanda. Also, it is important to indicate severe gaps in the evidence to inform policymaking, guide strategic planning, and improve healthcare and public health services, underscoring the urgent need to build national capacity in fungal diagnosis, surveillance, and research. Raising awareness among the public, scientific community, healthcare providers, and policymakers remains crucial. Furthermore, this report reveals the threats of FIs on public health and food insecurity in Rwanda. A multisectoral one health strategy is essential in research and intervention to determine and reduce the health and safety impacts of fungal pathogens on humans, animals, and the environment.

Evaluating eDNA and eRNA metabarcoding for aquatic biodiversity assessment: From bacteria to vertebrates

The monitoring and management of aquatic ecosystems depend on precise estimates of biodiversity. Metabarcoding analyses of environmental nucleic acids (eNAs), including environmental DNA (eDNA) and environmental RNA (eRNA), have garnered attention for their cost-effective and non-invasive biomonitoring capabilities. However, the accuracy of biodiversity estimates obtained through eNAs can vary among different organismal groups. Here we evaluate the performance of eDNA and eRNA metabarcoding across nine organismal groups, ranging from bacteria to terrestrial vertebrates, in three cross-sections of the Yangtze River, China. We observe robust complementarity between eDNA and eRNA data. The relative detectability of eNAs was notably influenced by major taxonomic groups and organismal sizes, with eDNA providing more robust signals for larger organisms. Both eDNA and eRNA exhibited similar cross-sectional and longitudinal patterns. However, the detectability of larger organisms declined in eRNA metabarcoding, possibly due to differential RNA release and decay among different organismal groups or sizes. While underscoring the potential of eDNA and eRNA in large river biomonitoring, we emphasize the need for differential interpretation of eDNA versus eRNA data. This highlights the importance of careful method selection and interpretation in biomonitoring studies.

Drivers of wood-inhabiting fungal diversity in European and Oriental beech forests

The hyperdiverse wood-inhabiting fungi play a crucial role in the global carbon cycle, but often are threatened by deadwood removal, particularly in temperate forests dominated by European beech (Fagus sylvatica) and Oriental beech (Fagus orientalis). To study the impact of abiotic drivers, deadwood factors, forest management and biogeographical patterns in forests of both beech species on fungal composition and diversity, we collected 215 deadwood-drilling samples in 18 forests from France to Armenia and identified fungi by meta-barcoding. In our analyses, we distinguished the patterns driven by rare, common, and dominant species using Hill numbers. Despite a broad overlap in species, the fungal composition with focus on rare species was determined by Fagus species, deadwood type, deadwood diameter, precipitation, temperature, and management status in decreasing order. Shifting the focus on common and dominant species, only Fagus species, both climate variables and deadwood type remained. The richness of species within the deadwood objects increased significantly only with decay stage. Gamma diversity in European beech forests was higher than in Oriental beech forests. We revealed the highest gamma diversity for old-growth forests of European beech when focusing on dominant species. Our results implicate that deadwood retention efforts, focusing on dominant fungi species, critical for the decay process, should be distributed across precipitation and temperature gradients and both Fagus species. Strategies focusing on rare species should additionally focus on different diameters and on the conservation of old-growth forests.

New prospects of environmental RNA metabarcoding research in biological diversity, ecotoxicological monitoring, and detection of COVID-19: a critical review

Ecosystems are multifaceted and complex systems and understanding their composition is crucial for the implementation of efficient conservation and management. Conventional approaches to biodiversity surveys can have limitations in detecting the complete range of species present. In contrast, the study of environmental RNA (eRNA) offers a non-invasive and comprehensive method for monitoring and evaluating biodiversity across different ecosystems. Similar to eDNA, the examination of genetic material found in environmental samples can identify and measure many species, including ones that pose challenges to traditional methods. However, eRNA is degraded quickly and therefore shows promise in detection of living organisms closer to their actual location than eDNA methods. This method provides a comprehensive perspective on the well-being of ecosystems, facilitating the development of focused conservation approaches to save at-risk species and uphold ecological equilibrium. Furthermore, eRNA has been recognized as a valuable method for the identification of COVID-19 in the environment, besides its established uses in biodiversity protection. The SARS-CoV-2 virus, which is accountable for the worldwide epidemic, releases RNA particles into the surrounding environment via human waste, providing insights into the feasibility of detecting it in wastewater and other samples taken from the environment. In this article, we critically reviewed the recent research activities that use the eRNA method, including its utilization in biodiversity conservation, ecological surveillance, and ecotoxicological monitoring as well as its innovative potential in identifying COVID-19. Through this review, the reader can understand the recent developments, prospects, and challenges of eRNA research in ecosystem management and biodiversity conservation.

Altitudinal Gradient and Soil Depth as Sources of Variations in Fungal Communities Revealed by Culture-Dependent and Culture-Independent Methods in the Negev Desert, Israel

We examined fungal communities in soil profiles of 0-10 cm depth along the altitudinal gradient of 250-530-990 m.a.s.l. at the Central Negev Desert, Israel, which benefit from similar annual precipitation (95 mm). In the soil samples collected in the summer of 2020, a mycobiota accounting for 169 species was revealed by both culture-dependent and culture-independent (DNA-based) methodologies. The impact of soil depth on the variations in fungal communities was stronger than the impact of altitude. Both methodologies displayed a similar tendency in the composition of fungal communities: the prevalence of melanin-containing species with many-celled large spores (mainly Alternaria spp.) in the uppermost layers and the depth-wise increase in the proportion of light-colored species producing a high amount of small one-celled spores. The culturable and the DNA-based fungal communities had only 13 species in common. The differences were attributed to the pros and cons of each method. Nevertheless, despite the drawbacks, the employment of both methodologies has an advantage in providing a more comprehensive picture of fungal diversity in soils.

RNA allows identifying the consumption of carrion prey

Facultative scavenging by predatory carnivores is a prevalent but frequently underestimated feeding strategy. DNA‐based methods for diet analysis, however, do not allow to distinguish between scavenging and predation, thus, the significance of scavenging on population dynamics and resource partitioning is widely unknown. Here, we present a methodological innovation to differentiate between scavenging and fresh prey consumption using prey RNA as a target molecule. We hypothesized that the rapid post‐mortem breakdown of RNA in prey tissue should lead to a significantly lower detection probability of prey RNA than DNA when carrion rather than fresh prey is consumed. To test this hypothesis, ground beetles (Pseudoophonus rufipes [De Geer]) were offered either fresh or 1‐day‐old dead Drosophila melanogaster fruit flies (carrion). The detectability of prey RNA and DNA in the beetles' regurgitates was assessed with diagnostic Drosophila‐specific RT‐PCR and PCR assays at 0, 6, 12, 24 and 48 h post‐feeding. After fresh fly consumption, prey RNA and DNA were detectable equally well at all times. When carrion prey was consumed, the detection strength of prey RNA immediately after feeding was significantly lower than that of prey DNA and reached zero in most samples within 6 h of digestion. Our findings provide evidence that prey RNA allows distinguishing between the consumption of fresh and scavenged prey, thereby overcoming a long‐known weakness of molecular diet analysis. The assessment of prey RNA offers a generally applicable approach for examining the importance of scavenging in food webs to unravel its functional consequences for populations, communities, and ecosystems.

Exploring the Taxonomic and Functional Diversity of Marine Benthic Micro-Eukaryotes Along the Red Sea Coast of Jeddah City

Backgrounds

Diverse marine habitats along Jeddah's Red Sea coast support rich biodiversity. Few studies have been done on its diverse communities, especially its microbial counterparts. Metagenomic analysis of marine benthic micro-eukaryotic communities was performed for the first time on the Red Sea coast of Jeddah. This research looks into their community structure and metabolic potential.

Methods

Next-generation sequencing was used to examine the micro-eukaryotic communities of seven sedimentary soil samples from four Jeddah coast locations. After isolating DNA from seven benthic sedimentary soil samples, the 18S rDNA V4 regions were amplified and sequenced on the Illumina MiSeq. It was also verified using an Agilent Technologies 2100 Bioanalyzer with a DNA 1000 chip (Agilent Technologies, Fisher Scientific). A standard curve of fluorescence readings generated by qPCR quantification using the Illumina library was achieved using the GS FLX library. Metagenomic data analysis was used to evaluate the microbial communities' biochemical and enzymatic allocations in studied samples.

Results

Blast analysis showed that the top ten phyla were Annelida, Eukaryota, Diatomea, Porifera, Phragmoplastophyta, Arthropoda, Dinoflagellata, Xenacoelomorpha Nematoda, and uncultured. Annelida was also found in the highest percentage (93%), in the sample M followed by Porifera (64%), the most abundant in the control sample then Eukaryotes (61%), Phragmatoplastophyta (55%), Arthropoda, and Diatomea (the least common) (32%). community diversity analysis: using Shannon and inverse Simpson indices showed sediment composition to be effective. Also, PICRUST2 indicated that the most abundant pathways were pyruvate fermentation to isobutanol, pyrimidine deoxyribonucleotide phosphorylation, adenosine ribonucleotide de novo biosynthesis, guanosine ribonucleotide de novo biosynthesis, NAD salvage pathway I, the super pathway of glyoxylate bypass and aerobic respiration I (cytochrome c).

Conclusion

Results showed that high throughput metagenomics could reveal species diversity and estimate gene profiles. Environmental factors appear to be more important than geographic variation in determining the structure of these microbial communities. This study provides the first report of marine benthic micro-eukaryotic communities found on the Red Sea coast of Jeddah and will serve as a good platform for future research.

Fungal dye-decolorizing peroxidase diversity: roles in either intra- or extracellular processes

Fungal dye-decolorizing peroxidases (DyPs) have found applications in the treatment of dye-contaminated industrial wastes or to improve biomass digestibility. Their roles in fungal biology are uncertain, although it has been repeatedly suggested that they could participate in lignin degradation and/or modification. Using a comprehensive set of 162 fully sequenced fungal species, we defined seven distinct fungal DyP clades on basis of a sequence similarity network. Sequences from one of these clades clearly diverged from all others, having on average the lower isoelectric points and hydropathy indices, the highest number of N-glycosylation sites, and N-terminal sequence peptides for secretion. Putative proteins from this clade are absent from brown-rot and ectomycorrhizal species that have lost the capability of degrading lignin enzymatically. They are almost exclusively present in white-rot and other saprotrophic Basidiomycota that digest lignin enzymatically, thus lending support for a specific role of DyPs from this clade in biochemical lignin modification. Additional nearly full-length fungal DyP genes were isolated from the environment by sequence capture by hybridization; they all belonged to the clade of the presumably secreted DyPs and to another related clade. We suggest focusing our attention on the presumably intracellular DyPs from the other clades, which have not been characterized thus far and could represent enzyme proteins with novel catalytic properties. KEY POINTS: • A fungal DyP phylogeny delineates seven main sequence clades. • Putative extracellular DyPs form a single clade of Basidiomycota sequences. • Extracellular DyPs are associated to white-rot fungi.