There have been sporadic reports of aquatic, benthic Microcoleus proliferations in freshwater rivers, lakes, and reservoirs for four decades, with reports increasing in frequency over the last twenty years, suggesting a possible rise in their global distribution, frequency, and intensity. Microcoleus can produce anatoxins which are neurotoxic, and ingestion of toxic mats has caused hundreds of dog fatalities and raised serious human and ecological health concerns. This review synthesizes and evaluates current knowledge on Microcoleus distribution, taxonomy, toxin production, toxicity, ecology, environmental drivers, and biotic interactions. Toxin-producing Microcoleus have been reported in at least 18 countries, though many regions have not conducted toxin testing, suggesting a broader but under-reported distribution. Proliferations occur across diverse habitats, including cobble-bedded streams, large sandy rivers, reservoirs, and lakes. Microcoleus proliferations also occur on macrophytes, both in lakes and rivers. Genomic analyses currently classify anatoxin-producing Microcoleus into distinct species, with all known anatoxin-producers isolated from freshwater ecosystems. Anatoxin concentrations vary widely over space and time, within and among waterbodies. While studies on environmental drivers remain limited, research in cobble-bedded rivers suggests that moderate enrichment of dissolved inorganic nitrogen and low dissolved reactive phosphorus concentrations in the water column promote proliferation. Metagenomic approaches have revealed unique nutrient acquisition and storage strategies used by Microcoleus. Key knowledge gaps remain around the environmental and ecological triggers of proliferation, toxin production, genomic diversity and microbial interactions. Addressing these gaps through coordinated, global studies using robust datasets and consistent methods is critical to improve prediction, monitoring, and mitigation of this increasingly widespread public and ecological health threat.

Pharmaceutical residues are persistent contaminants that resist conventional wastewater treatment and can disrupt ecosystems; however, microorganisms provide a promising biobased solution to transform or mineralize these complex xenobiotics. Whether pollutant-adapted communities maintain their degradative capacity under realistic environmental conditions remains a long-standing debate in environmental biotechnology. Here, microbial consortia enriched in six membrane bioreactors under high pharmaceutical concentration (100 mg/L) retained full biodegradation capacity across a 5000-fold concentration range. After prolonged exposure to six model compounds (atenolol, caffeine, diclofenac, enalapril, ibuprofen, and paracetamol) complete removal occurred for all except diclofenac. Degradation remained efficient even at lower and environmentally relevant concentrations (1 mg/L-20 µg/L) and recovered rapidly upon re-exposure to higher loads (100 mg/L). Metagenomic profiling revealed enrichment of oxygenase-mediated catabolic pathways supporting this resilience. When transferred to a 7 liters bioreactor treating real wastewater, the adapted community removed targeted and untargeted pharmaceuticals, demonstrating robustness, scalability, and strong potential for sustainable micropollutant remediation.

In heterogeneous environments, the hyphae of filamentous fungi and oomycetes can facilitate the dispersal of other microorganisms. The use of these "fungal highways" (FH) is regulated by both physical and biological factors with their interplay resulting in variable capabilities of different microbes to establish FH. Several devices have been developed to test the movement of bacteria across mycelium. However, these methods are usually time-consuming and cannot be applied at a large scale. In this study, we developed 3D-printed experimental devices that physically separate two environments while allowing hyphal networks to act as bridges for bacterial movement. The final design allows for the simultaneous testing of up to 10 pairs and the inclusion of any culturing media. With these devices, we investigated how fungal-bacterial pairing, nutrient conditions, and inoculation strategies influence FH formation. Bacterial transport was limited in nutrient-rich media but increased under poorer nutrient conditions, consistent with enhanced exploratory growth of the mycelium. Both cis- and trans-inoculation supported FH formation, although bacterial arrival was delayed in the absence of co-inoculation. The devices were used to demonstrate that transport of bacteria by FH was relevant for the colonization of a natural substrate. Finally, we established a novel in planta assay to evaluate FH formation during host colonization. This assay demonstrated that Fusarium graminearum can transport bacteria during wheat spike colonization. Together, these results provide accessible, scalable tools to study hyphal-mediated bacterial dispersal and highlight the combined role of biological specificity and nutrient context in the establishment of FH.

Toxic species within the benthic Microcoleus cyanobacterial genus pose significant ecological and public health risks due to the production of the potent neurotoxin anatoxin. In Switzerland, Microcoleus anatoxicus, a known producer of anatoxin derivatives, has caused several dog fatalities causing alarm among the public and authorities. Similar incidents worldwide have been associated with various Oscillatoriales cyanobacteria. While previous studies have explored the microbial diversity within Microcoleus mats, annual spatiotemporal dynamics in lotic systems remain poorly understood. In this study, sediment samples at defined locations along the Areuse river (Neuchâtel) were collected for a year. Together with measurements of the local environmental parameters, the associated bacterial and eukaryotic communities were characterized using the 16S and 18S rRNA genes, respectively. Anatoxin-producing capacity was inferred using PCR of the anaC gene. The results show that while environmental parameters differed significantly over time, microbial communities differed significantly between sites. Bacterial communities showed relatively high abundances of cyanobacteria, specifically Microcoleus, which corresponded to up to 56% of all cyanobacteria. Furthermore, anaC PCR results were negative suggesting the dominance of non-toxic Microcoleus. Relative abundance of Microcoleus was highest between spring and summer, corresponding to up to 37% of the total bacterial communities. Significant positive correlations (approximately 64%) were observed between Microcoleus and other organisms such as rotifers, nematodes and chytrids. These positive relationships might highlight potential interactions between Microcoleus and predators. This is the first study of benthic microbial populations in a Swiss river. This study advances our understanding of benthic cyanobacterial ecology and provides insights into natural mechanisms that may mitigate toxin-related risks in freshwater environments. Moreover, the results highlight the prevalence of non-toxic Microcoleus on epilithic substrates suggesting its role in the establishment of microbial communities in the benthos.

The gut microbiome of Lepidopteran insects is highly dynamic, influenced by both host diet and phylogeny. While microbial communities are thought to facilitate host adaptation to diverse diets and environments, the existence of a core microbiome shared among closely related herbivores remains largely untested. In this study, we examined the microbial communities in the regurgitant of four Spodoptera species (S. exigua, S. frugiperda, S. latifascia, and S. littoralis) across different diets (artificial diet, cotton, maize, and squash). Using a high-throughput sequencing, we characterized bacterial and fungal community composition and diversity. Bacterial communities were shaped by both diet and host species, indicating species-specific bacterial selection. In contrast, fungal communities were exclusively structured by diet, with lower diversity and dominance of a few key taxa. Notably, no operational taxonomic units were consistently shared across all species or diets, challenging the concept of a conserved core microbiome in these generalist herbivores. Understanding how microbial communities shape generalist herbivores’ ability to feed on diverse plants may offer potential strategies for microbiome-based pest management.

Electrical signaling is a crucial mechanism for intercellular communication across diverse biological systems. Despite evidence of electrical activity in fungal mycelia, a standardized, reproducible method for detecting these signals is lacking. In this study, we developed a novel approach using printed circuit boards with embedded differential electrodes to record extracellular voltage fluctuations in mycelium. By incorporating a Faraday cage and short-time Fourier transform analysis, we minimized noise and extracted relevant frequency patterns. Our findings revealed electrical activity correlated with fungal growth that varied with biocide treatments. The results support the biological origin of these signals, suggesting a role in environmental adaptation. This study provides a robust framework for further exploration of fungal electrophysiology, with implications for understanding signaling mechanisms in mycelial networks.

SUMMARY This study characterizes the ecophysiological responses and growth dynamics of Nitzschia palea isolated from Salar de Huasco, Chile, a high‐altitude wetland located at 3800 m above sea level. The culture was maintained at 17°C under cool‐white fluorescent light with a 14:10 h light/dark photocycle and a photon flux of 50 μmol photons m − 2 s −1 . The diatom was identified morphologically and genetically, with phylogenetic analysis confirming its close relationship to known N. palea strains. Photophysiological responses were measured along with a series of media and temperature conditions in N. palea strain. Modified f/2 media supplemented with different concentrations of Si, Se and vitamins were tested. Subsequently, growth in the double‐Si f/2 media was assessed at three different temperatures. Lastly, the diatom strain was incubated at 17°C and 27–29°C in f/2 + double‐Si (NN: non‐extra nutrient addition) and a highly eutrophic state of f/2 (WN: with nutrient enrichment addition). The highest growth was observed using the f/2 media WN at 17°C (day 5, 4.46 × 10 5 ± 3.15 × 10 4 SD cells mL −1 ). Temperature significantly influenced growth; 17°C supported higher cell densities and more stable photosynthetic parameters compared 27–29°C. Nutrient enrichment further enhanced photosynthetic efficiency (αETR) and maximal quantum yield ( F v / F m ), particularly under control temperature conditions. Photosynthetic performance, assessed via rapid light‐response curves, showed significant temperature and nutrient dependent variation. Nitzschia palea cultures at 27–29°C exhibited increased in relative maximal ETR (rETR max ,184.1 μmol m −2 s −1 ) compared to control conditions. In nutrient enriched treatments, photosynthetic efficiency peaked on day 5, but declined by day 8. These findings highlight the adaptive capacity of N. palea to fluctuating environmental conditions and underscore its potential as a model organism for studying diatom responses to nutrient and temperature stress in extreme ecosystems.

Bacterial-fungal interactions (BFIs) play an integral role in shaping microbial community composition, biogeochemical functions, spatial dynamics, and microbial dispersal. Mycelial networks created by filamentous fungi or other filamentous microorganisms (e.g., Oomycetes) act as 'fungal highways' that can be utilized by bacteria for transport throughout heterogeneous environments, greatly facilitating their mobility and granting them access to regions that may be challenging or impossible to reach on their own (e.g., due to air pockets within the soil). Several devices and experimental protocols have been created to study these fungal highways, including fungal highway columns. The fungal highway column designed by our group can be used for a variety of in situ or in vitro applications, as well as with diverse environmental and host-associated sample types. Herein, we describe the methods for performing experiments with these columns, including designing, printing, sterilizing, and preparing the devices. The options for analyzing data obtained from the use of these devices are also discussed here, and troubleshooting advice regarding potential pitfalls associated with experiments using fungal highway columns is offered. These devices can be used to gain a more comprehensive understanding of the diversity, mechanisms, and dynamics of fungal highway BFIs to provide valuable insights into the structural and functional dynamics within complex environments (e.g., soils) and across diverse habitats in which bacteria and fungi co-exist.

We report the complete genome sequence of the Niallia sp. strain Kr1, a gram-negative, spore-forming bacterium isolated from the geothermal fluids of an Icelandic geothermal power plant injection well. This strain belongs to a putative new species within the Niallia genus.

Incomplete degradation of oxalate, a compound commonly found in the diet, can lead to disease in humans, particularly affecting the kidneys. The concentration of oxalate in the body depends on several factors, one of which is intestinal absorption—an aspect influenced by oxalotrophy among enteric bacteria. Despite its potential significance, oxalotrophy in the human microbiome remains poorly understood. In this study, we conducted a systematic search for the co-occurrence of three key oxalotrophy genes—frc, oxc, and oxlT. We developed and validated specific conservation models for each gene and applied them to genomes and metagenomes associated with the human digestive tract, oral cavity, and lungs. Our analysis revealed that oxalotrophy, defined as the capacity to use oxalate as an energy source, is a rare metabolic trait predominantly confined to the gut. We also found evidence that this capacity can be acquired via horizontal gene transfer. While oxalotrophy is relatively uncommon, the broader capacity for oxalate degradation is more widespread. Notably, the genes frc and oxc are frequently found in close proximity within genomes, suggesting a selective advantage for organisms possessing this capability. Incomplete degradation of oxalate, a compound commonly found in the diet, can cause disease in humans, particularly affecting the kidney. Its concentration in the body depends on several factors, one of which is intestinal absorption, which is itself affected by oxalotrophy among enteric bacteria. Oxalotrophy in the human microbiome is poorly known. In this study, we perform a systematic search for the simultaneous presence of the three oxalotrophy genes, namely frc, oxc and oxlT. Thanks to the construction and validation of specific conservation models for all three genes, we were able to search for oxalotrophy in genomes and metagenomes associated with the human digestive tract, oral cavity, and lungs. We report that oxalotrophy—the capacity to use oxalate as an energy source—is a rare metabolic trait, mostly confined to the gut, and also find evidence that it can be acquired by horizontal gene transfer. By contrast, the capacity for oxalate degradation is more widespread, and two genes responsible for it (frc and oxc) are almost always close together in the genome, suggesting selection pressure.

The movement of bacteria on the hyphae of fungi and other mycelial-forming organisms is an important process that determines their ability to actively disperse in water-unsaturated habitats. However, direct observation and characterization of bacterial cell movement on mycelial networks have been difficult to achieve. In this study, we developed a new method that uses high-speed video recording to track the dispersal of individual fluorescently tagged cells of two closely related strains of Pseudomonas putida (UWC1 and KT2440) over the mycelial network of the oomycete Pythium ultimum. We found high intra-population heterogeneity and between-population differences in dispersal speeds for the two bacterial strains. The fitting of the speed distribution functions led to the separation of speeds into two ranges (fast/slow) at an intersection of the fitted curves. In the lower speed range, the UWC1 strain dispersed faster, while the KT2440 strain moved faster in the higher speed range. This finding helps explain conflicting competition outcomes revealed in previous studies and suggests that population mean speed alone does not capture key aspects of bacterial dispersal in mycelial networks. Our new method opens the possibility of studying bacterial dispersal, competition, and other social interactions in spatially heterogeneous environments, such as soils.

The phytopathogenic fungus Sclerotinia sclerotiorum has a wide host range and causes significant economic losses in crops worldwide. This pathogen uses oxalic acid as a virulence factor; for this reason, the degradation of this organic acid by oxalotrophic bacteria has been proposed as a biological control approach. However, previous studies on the potential role of oxalotrophy in biocontrol did not investigate the differential effect of oxalic acid consumption and the subsequent pH alkalinisation on fungal growth. In this study, confrontation experiments on different media using a wild-type (WT) strain of S. sclerotiorum and an oxalate-deficient mutant (strain Δoah) with the soil oxalotrophic bacteria Cupriavidus necator and Cupriavidus oxalaticus showed the combined effect of media composition on oxalic acid production, pH, and fungal growth control. Oxalotrophic bacteria were able to control S. sclerotiorum only in the medium in which oxalic acid was produced. However, the deficient Δoah mutant was also controlled, indicating that the consumption of oxalic acid is not the sole mechanism of biocontrol. WT S. sclerotiorum acidified the medium when inoculated alone, while for both fungi, the pH of the medium changed from neutral to alkaline in the presence of bacteria. Therefore, medium alkalinisation independent of oxalotrophy contributes to fungal growth control.

Aspergillus fungi are opportunistic pathogens that affect millions of people worldwide. Aspergilli produce organic acids to optimize the environmental pH and match the needs of their enzymatic machinery. In this study, we tested the hypothesis that this also occurs during infection. By producing oxalic acid (OA), Aspergillus would manipulate pH during lung infection and thus, interfering with this process could control the pathogen. To test this hypothesis, we assessed in silico the potential for OA production in a wide range of Aspergilli. A genetic marker for AO production was detected in most of the species including prevalent human pathogens. We tested OA production in vitro in four strains of A. niger and A. fumigatus, but only one of the A. niger strains produced OA consistently. For this fungal strain, oxalotrophic bacteria were able to control fungal growth via OA consumption. To translate this observation into a pre-clinical system, increasingly complex experiments were performed. In 3D-cell cultures, A. niger also secreted OA and modified pH and free Ca2+. Co-inoculation of the oxalotrophic bacterium inhibited the development of the fungus. However, biocontrol could not be replicated in Galleria mellonella, which is often used as an infection model. In contrast, the bacterium improved disease score and the absence of oxalate crystals in the lungs in the mouse model. This biocontrol interaction between oxalotrophic bacteria and A. niger represents a paradigm shift in the fight against opportunistic fungal pathogens, where the goal is to render the host environment less permissive to pathogen development. ### Competing Interest Statement The authors have declared no competing interest.

One solution for reducing the scaling risk of lead (Pb)-containing phases consists of removing the aqueous Pb2+ ions from the brine by sorption before oversaturation at unwanted locations within the geothermal fluid loop. Hence, this study investigated the known capacity of fungal biomass to biosorb Pb2+ ions to remove Pb2+ from the brine. So far, biosorption studies have neither been done at high temperatures or salinity, nor under high pressure, three conditions that must be considered within geothermal power plants. Thus, the overall goal of this study was to assess the Pb2+ biosorption potential of dead biomass of the fungus Penicillium citrinum strain HEK1 under conditions mimicking those of natural highly saline geothermal fluids. This specific strain was isolated from geothermal brine circulating in a plant in which Pb2+ scaling occurs. To assess biosorption, dead biomass of P. citrinum was added to synthetic solutions containing 260 g/L NaCl, 1 g/L Pb, and (in half of the treatments) 60 mg/L acetic acid. These synthetic solutions, including the dead biomass, were then incubated at high pressure (8 bar), at different temperatures (25 °C, 60 °C, 98 °C), and for different time intervals (1 h, 2 h, 3 h). Results showed that the structure of the biomass was stable in such conditions, at all temperatures tested, but small amounts of organic compounds, with a wide variety of low molecular weight (< 350 Da to 10,000 Da) were released into the fluids from the biomass. In general, increased temperature resulted in an increase in dissolved organic carbon (DOC) concentration. The biosorption potential of P. citrinum HEK1 biomass was overall low (0.72

Morels are iconic macrofungi known for their culinary value and spring emergence. Molecular phylogenetic studies have hitherto failed to elucidate the evolution of the ecological lifestyles of true and false morels, impeding their capacity to resolve longstanding debates regarding the extent of their saprotrophy and the potential for biotrophic associations with plants. In this study, we examined the evolutionary history and molecular innovations of Morchellaceae by generating high-quality genomes from species encompassing all the major clades within this family. We used conserved single-copy orthologs to infer the evolutionary history of true and false morels and related truffles. The genome size, transposable element content, and polysaccharide-degrading enzyme gene content are consistent with an ectomycorrhizal lifestyle for the Morchellaceae truffles Leucangium carthusianum and Kalapuya brunnea, whereas the other clades, including all true morels (Morchella spp.), exhibited genomic signatures of saprotrophic habits characterized by a highly conserved set of genes encoding plant biomass-related degrading enzymes. Morchellaceae species were found to be predominantly heterothallic, with either the MAT1-1 or MAT1-2 loci; however, the occurrence of colocalized mating-type idiomorphs, indicative of homothallism, was observed in M. rufobrunnea, M. peruviana, L. carthusianum, and the outgroup taxon Gyromitra esculenta. This study revealed a wealth of largely undiscovered genomic traits, including saprotrophic potential within Morchellaceae and a lack of biotrophic markers, and contributes to our understanding of the intricate evolutionary trajectories of the modes of nutrition in soil fungi.

In February 2023, the French government launched an action plan to accelerate the development of geothermal energy, in particularly deep geothermal energy. In March 2024, a parliamentary information mission presented its recommendations. While the seismic risk is well-known in France, illustrated by a set of earthquakes that occurred in Alsace between 2019 and 2021, the health impacts of deep geothermal energy are rarely addressed in the literature. Here, we review the impacts and potential health hazards for exposed populations. After recalling that many populations live in geothermal regions, we underline the health benefits of thermal springs and the economic interest of geothermal resources. We then present its geological origins and the physicochemical characteristics of geothermal fluids, pointing to the microbiological ecosystem in the lithosphere. The exploitation of high-energy deep geothermal energy involves several technical stages, including drilling which provides access to the resource, the production system, the use of energy, the treatment of (potential) discharges into the environment, and the natural management of radioactivity. We consider the environmental and health risks and impacts linked to the resource and its exploitation, some known accidents and, in a few countries, epidemiological studies particularly those concerning cancers and gas emissions, before addressing the monitoring and epidemiology of these impacts in France.

Electrical signaling is a fundamental mechanism for integrating environmental stimuli and coordinating responses in living organisms. While extensively studied in animals and plants, the role of electrical signaling in fungi remains a largely underexplored field. Early studies suggested that filamentous fungi generate action potential-like signals and electrical currents at hyphal tips, yet their function in intracellular communication remained unclear. Renewed interest in fungal electrical activity has fueled developments such as the hypothesis that mycorrhizal networks facilitate electrical communication between plants and the emerging field of fungal-based electronic materials. Given their continuous plasma membrane, specialized septal pores, and insulating cell wall structures, filamentous fungi possess architectural features that could support electrical signaling over long distances. However, studying electrical phenomena in fungal networks presents unique challenges due to the microscopic dimensions of hyphae, the structural complexity of highly modular mycelial networks, and the limitations of traditional electrophysiological methods. This review synthesizes current evidence for electrical signaling in filamentous fungi, evaluates methodological approaches, and highlights experimental challenges. By addressing these challenges and identifying best practices, we aim to advance research in this field and provide a foundation for future studies exploring the role of electrical signaling in fungal biology.

Toxic benthic cyanobacterial mats have been identified globally as a potential health hazard since they can produce potent cyanotoxins. Such mats have been connected to the death of mammals worldwide, with a significant fraction of recent cases associated to benthic cyanobacterial blooms producing anatoxin-a or its derivatives. A recent event involving the death of a dog led to monitoring of mats in the area and to the discovery of the first cyanopeptolin producer among the genus Phormidium. Using metagenomics, the genome of the dominant species in the cyanobacterial mats collected was reconstructed, but no evidence for the production of anatoxin-a or other congeners was obtained. In contrast, the biosynthetic gene cluster for cyanopeptolin was detected in the genome. Further chemical analysis of metabolites extracted from the same mats enabled the isolation and characterization of two novel cyanopeptolins with their truncated products. Toxicity was confirmed using the cytotoxic reporting organism Thamnocephalus platyurus. The untruncated cyanopeptolins had an LC50 as low as 6.4 μM while the truncated products did not exhibit cytotoxicity in the same assay. The presence of truncated analogues lacking cytotoxicity might suggest that other mat-associated microorganisms could degrade those compounds. While Phormidium may not be the direct cause of dog's death, our study provides the first evidence that Phormidium can produce cyanopeptolins. This highlights the underexplored variety of neglected cyanotoxin classes. These findings not only expand the known chemical diversity of cyanotoxins but also raise concerns regarding the potential ecological impact of toxic Ahp-cyclodepsipeptides in freshwater environments.

ABSTRACTThe inadequate removal of pharmaceuticals and personal care products (PPCPs) by traditional wastewater treatment plants (WWTPs) poses a significant environmental and public health challenge. Residual PPCPs find their way into aquatic ecosystems, leading to bioaccumulation in aquatic biota, the dissemination of antibiotic resistance genes (ARGs), and contamination of both water sources and vegetables. These persistent pollutants can have negative effects on human health, ranging from antibiotic resistance development to endocrine disruption. To mitigate these risks, there is a growing interest in exploiting microorganisms and their enzymes for bioremediation purposes. By harnessing the metabolic capabilities of microbial communities, PPCPs can be efficiently degraded, transformed, or sequestered in water systems. Additionally, microbial communities exhibit remarkable adaptability and resilience to diverse PPCP contaminants, further underscoring their potential as sustainable and cost‐effective solutions for water treatment. This review explores the promise of microbial bioremediation as an approach to addressing the complex challenges posed by persistent PPCP contamination, emphasising its potential to safeguard both environmental integrity and human well‐being.