Extreme Ecosystems Research Articles

Beyond traditional screening: Unveiling antibiotic potentials of actinomycetes in extreme environments

Extreme ecosystems are a rich source of specialized metabolites that can overcome multidrug resistance. However, the low efficiency of traditional exploratory research in discovering new antibiotics remains a major limitation. We hypothesized that actinomycetes may have the ability to produce antibiotics in the extremes of a changing natural environment. This study introduces a novel approach to screening natural antibiotic producers from extreme habitats based on the relationship between organisms' adaptive traits and their metabolic activities. The antibacterial and antifungal properties of 667 actinomycete isolates, obtained from 160 samples of Kazakhstan's diverse extreme habitats, were studied under neutral, saline, and alkaline conditions against MRSA, E. coli, C. albicans, and A. niger. Among these isolates, 113 exhibited antibacterial properties, and 109 demonstrated antifungal properties. Notably, one-fifth of the antagonist isolates could produce active substances solely under extreme growth conditions. Fifty-three antagonistic actinomycetes, possessing these characteristics, have been categorized into groups and warrant further investigation as potential producers of new natural antibiotics. Molecular genetic analysis of the selected isolates revealed a high prevalence of Streptomyces and Nocardiopsis strains. Furthermore, 83.4 % of obtained isolates demonstrated the ability to thrive in all studied habitats—neutral, saline, and alkaline. 96.3 % of actinomycetes isolated from extreme environments exhibited adaptation to neutral conditions, highlighting their inherent versatility. Our findings underscore the nearly complete potential (99.7 %) of isolates to overcome the salinity barrier of 3.5 % NaCl, indicating their capacity to inhabit oceanic environments. We assert that actinomycetes should be perceived as a cohesive, globally adaptive group, capable of migrating between changing conditions or remaining stable within them. These studies lay the groundwork for the development of a new platform for screening natural antibiotics.

Chromosome-scale genome assembly of the mangrove climber species Dalbergia candenatensis

Consisting of trees, climbers and herbs exclusively in the intertidal environments, mangrove forest is one of the most extreme and vulnerable ecosystems of our planet and has long been of great interest for biologists and ecologists. Here, we first assembled the chromosome-scale genome of a climber mangrove plant, Dalbergia candenatensis. The assembled genome size is approximately 474.55 Mb, with a scaffold N50 of 48.1 Mb, a complete BUSCO score of 98.4%, and a high LTR Assembly Index value of 21. The genome contained 283.46 Mb (59.74%) repetitive sequences, and 29,554 protein-coding genes were predicted, of which 87.54% were functionally annotated in five databases. The high-quality genome assembly and annotation presented herein provide a valuable genomic resource that will expedite genomic and evolutionary studies of mangrove plants and facilitate the elucidation of molecular mechanisms underlying the salt- and water-logging-tolerance of mangrove plants.

Phytoplankton Communities' Seasonal Fluctuation in Two Neighboring Tropical High-Mountain Lakes.

High-mountain lakes (HMLs) are remote, extreme, and sensitive ecosystems recognized as sentinels of global change. Lakes El Sol and La Luna are very close to each other inside the crater of the Nevado de Toluca volcano, but they differ morphometrically and limnologically. This study aimed to identify the seasonal fluctuation of the phytoplankton communities of these two tropical HMLs. El Sol phytoplankton comprised 50 taxa (chlorophytes, diatoms, charophytes) and La Luna 28 taxa (diatoms, euglenoids). The abundance of phytoplankton in El Sol was three times higher than in La Luna, and the biomass in El Sol was five times higher than in La Luna. Tropical seasonality was reflected differently in each lake. In El Sol, the highest phytoplankton abundance occurred in the rainy season, while the highest biomass was recorded in the dry/warm season. Conversely, in La Luna, abundance and biomass were more prominent in the dry/cold season. The study found that no meteorological or limnological factors could explain the seasonal dynamics of the taxonomic richness, abundance, or biomass of the phytoplankton communities in both lakes. The differences between the lakes are likely due to the more extreme conditions of La Luna, such as lower pH, ultra-oligotrophy, and increased exposure to ultraviolet radiation (UVR). Additionally, the introduction of rainbow trout into El Sol in the 1950s may have also contributed to the differences.

Metagenomic characterization of viruses and mobile genetic elements associated with the DPANN archaeal superphylum.

The archaeal superphylum DPANN (an acronym formed from the initials of the first five phyla discovered: Diapherotrites, Parvarchaeota, Aenigmarchaeota, Nanohaloarchaeota and Nanoarchaeota) is a group of ultrasmall symbionts able to survive in extreme ecosystems. The diversity and dynamics between DPANN archaea and their virome remain largely unknown. Here we use a metagenomic clustered regularly interspaced short palindromic repeats (CRISPR) screening approach to identify 97 globally distributed, non-redundant viruses and unclassified mobile genetic elements predicted to infect hosts across 8 DPANN phyla, including 7 viral groups not previously characterized. Genomic analysis suggests a diversity of viral morphologies including head-tailed, tailless icosahedral and spindle-shaped viruses with the potential to establish lytic, chronic or lysogenic infections. We also find evidence of a virally encoded Cas12f1 protein (probably originating from uncultured DPANN archaea) and a mini-CRISPR array, which could play a role in modulating host metabolism. Many metagenomes have virus-to-host ratios >10, indicating that DPANN viruses play an important role in controlling host populations. Overall, our study illuminates the underexplored diversity, functional repertoires and host interactions of the DPANN virome.

Pathogenicity of psychrotolerant strains of Antarctic Pseudogmynoascus fungi reveals potential opportunistic profiles

Recent studies have demonstrated the presence of fungal taxa in the extreme ecosystems of Antarctica that are known to opportunistically infect humans and animals. Among these are members of the genus Pseudogymnoascus, including some that are genetically similar to P. destructans, known to be pathogenic to bats. We evaluated the in vitro and in vivo pathogenic potential of 11 Pseudogymnoascus spp. strains recovered from Antarctica. All strains were able to grow at temperatures up to 28 °C and displayed in vitro pathogenicity through hemolytic activity, growth at different pH levels, production of hydrolytic enzymes, spore diameters, tolerance to oxidative stress, hypoxia, and halotolerance. Among them, Pseudogymnoascus sp. UFMG 8532 exhibited strong in vitro pathogenicity and in preliminary in vivo assay killed 100 % of Tenebrio molitor larvae within one day. The pathogenicity of the same strain was also tested using immunosuppressed BALB/c mouse models. Survival of BALB/c mice was affected, with oscillations between weight gain and loss, and impacts on sensory function, reflexes and autonomic function. Histopathological data from the organs of infected mice showed evidence of inflammatory processes, with numerous neutrophils, a small number of macrophages, fluid accumulation inside the lungs and intense hyperemia. Our results indicate that Antarctic Pseudogymnoascus spp. strains obtained from various substrates/habitats in maritime Antarctica may possess intrinsic virulence factors and pathogenic potential for immunosuppressed animals and humans in the region. Given that the Antarctic environment is an important reservoir for Pseudogymnoascus species, which display growth performance across a range of temperatures, it is possible that increasing temperatures in the maritime Antarctic could activate dormant genes or biochemical pathways, select virulent species and/or strains, and facilitate their spread within and beyond the region. The ability of Pseudogymnoascus species to grow slowly even at 28°C, coupled with their potential in vitro and in vivo virulence factors, suggests that these fungi might be undergoing an opportunistic transition due to the effects of climate change on the Antarctic Peninsula.

Assessment of coral reef connectivity in improved organic carbon storage of seagrass ecosystems in Palk Bay, India

The increase in climate-related extreme events and ecosystem degradation demands consistent and sustainable climate mitigation efforts. Seagrass playing a key role in nature-based carbon sequestration mitigation strategy. Here, we investigated the role of coral reef connectivity in blue carbon dynamics with seagrass meadows with coral reef connectivity (SC areas) and without coral reef connectivity (SG areas) in Palk Bay, India. The high sediment organic carbon was recorded in SC areas (90.26 ± 25.68 Mg org.C/ha) and lower in SG areas (66.96 ± 12.6 Mg org.C/ha). The maximum above-ground biomass (AGB) was recorded in Syringodium isoetifolium (35.43 ± 8.50) in SC areas and the minimum in Halophila ovalis (7.59 ± 0.90) in SG areas, with a similar trend observed in below-ground biomass (BGB). Our findings highlight the importance of coral reefs in enhancing the blue carbon potential of seagrass ecosystems and underscore the need for integrated conservation and restoration strategies for coral reefs and seagrasses.

Positive selection in cilia-related genes may facilitate deep-sea adaptation of Thermocollonia jamsteci

Deep-sea hydrothermal vents are characterized by high hydrostatic pressure, hypoxia, darkness and toxic substances. However, how organisms adapt to such extreme marine ecosystems remain poorly understood. We hypothesize that adaptive evolution plays an essential role in generating novelty for evolutionary adaptation to the deep-sea environment because adaptive evolution has been found to be critical for species origin and evolution. In this project, the chromosome-level genome of the deep-sea hydrothermal vent gastropod T. jamsteci was constructed for the first time to examine molecular mechanisms of its adaptation to the deep-sea environment. The genome size was large (2.54 Gb), ranking at the top of all species in the Vetigastropoda subclass, driven primarily by the bursts of transposable elements (TEs). The transposition of TEs may also trigger chromosomal changes including both inter-chromosomal fusions and intra-chromosomal activities involving chromosome inversions, rearrangements and fusions, as revealed by comparing the genomes of T. jamsteci and its closely related shallow-sea species Gibbula magus. Innovative changes including the expansion of the ABC transporter gene family that may facilitate detoxification, duplication of genes related to endocytosis, immunity, apoptosis, and anti-apoptotic domains that may help T. jamsteci fight against microbial pathogens, were identified. Furthermore, comparative analysis identified positive selection signals in a large number of genes including the hypoxia up-regulated protein 1, which is a chaperone that may promote adaptation of the T. jamsteci to hypoxic deepsea environments, hox2, Rx2, Pax6 and cilia-related genes BBS1, BBS2, BBS9 and RFX4. Notably, because of the critical importance of cilia and IFT in development, positive selection in cilia-related genes may play a critical role in facilitating T. jamsteci to adapt to the high-pressure deep-sea ecosystem. Results from this study thus revealed important molecular clues that may facilitate further research on the adaptation of molluscs to deep-sea hydrothermal vents.

Impacts of coyote colonization on coastal mammalian predators

Extreme ecosystem modification by humans has caused drastic reductions in populations and ranges of top mammalian predators, while simultaneously allowing synanthropic mesopredator species to expand. These conditions often result in inflated local densities of highly adaptable mesopredators that disrupt trophic dynamics and place unsustainable predation pressure on native prey populations. Colonization of a dominant predator may lead to top-down control of mesopredators and restore trophic balance. Coyotes are a novel colonizer of some coastal barrier islands of eastern North America, offering an opportunity to test how the addition of an apex predator impacts an established guild of mesopredators. To assess their trophic impact, we conducted 75,576 camera trapping hours over an 18-month study period, capturing > 1.5 million images across 108 coastal camera sites. Using two-species occupancy and habitat use models, we found sizeable effects of coyote habitat use on that of red foxes and free-ranging domestic cats, suggesting that coyotes function as apex predators in barrier island ecosystems. In fact, the only factor that determined the spatial pattern of highly ubiquitous red foxes was the sympatric habitat use of the largest carnivore in the food web—coyotes. That ‘novel’ apex predators can become established in coastal food webs illustrates the highly dynamic nature of conservation challenges for habitats and species at the edge of the sea.

Exploring the biodiversity of Antarctic cyanobacteria: A review of secondary metabolites and their applications

Cyanobacteria are photosynthetic microorganisms widely distributed in diverse environments, including Antarctica, one of the most extreme ecosystems on the planet. These microorganisms have the unique ability to produce a variety of secondary metabolites with bioactive properties. The cyanobacteria that thrive in Antarctica hold exceptional biotechnological promise as they consistently meet and overcome the challenges of this demanding environment by producing a range of diverse secondary metabolites tailored for survival and adaptation. Therefore, this review article aims to explore the secondary metabolites produced by Antarctic cyanobacteria and their potential application in different industries, including pharmacology, cosmetics, and agriculture. Four hundred and twenty-one data were collected from articles reporting the search for metabolites produced by Antarctic cyanobacteria, published between 1989 and 2023, with the years 2000, 2008, and 2014 contributing more than half of this data. Around 29.2 % of the articles surveyed focused on secondary metabolites, 61 % on biotechnological potential, and 9.7 % on specific genes. These results demonstrate that Antarctica's unique and extreme environment is as a remarkable natural laboratory for studying cyanobacteria and their diverse secondary metabolites.

A two‐year physicochemical and acoustic observation reveals spatiotemporal effects of earthquake‐induced shallow‐water hydrothermal venting on the surrounding environments

AbstractShallow‐water hydrothermal vents have gained growing attention for their intricate characteristics caused by various epipelagic factors. The shallow‐water hydrothermal system offshore Kueishan Island, Taiwan, situated in an earthquake‐prone area, has prompted our exploration into the relationship between hydrothermal and seismic activities. Our 2‐yr observation uncovered that the hydrothermal venting entered a silent period in November 2020, followed by a resurgence of activity after September 2021, coinciding with high‐frequency shallow earthquakes occurring within 5 km of the vents. The pH level, dissolved inorganic carbon, alkalinity, pCO2, , and sulfide served as indicators of hydrothermal activity, contributing to environmental changes in habitats during period transition. However, peering physicochemical and soundscape conditions, distinctions may still arise during two separate active periods. Through multivariate analysis, this study highlights the variability of shallow‐water hydrothermal vents, emphasizing the necessity for more frequent and detailed investigations to further understand these extreme and dynamic marine ecosystems.

Heterologous expression and structure prediction of a xylanase identified from a compost metagenomic library

Xylanases are key biocatalysts in the degradation of the β‐1,4‐glycosidic linkages in the xylan backbone of hemicellulose. These enzymes are potentially applied in a wide range of bioprocessing industries under harsh conditions. Metagenomics has emerged as powerful tools for the bioprospection and discovery of interesting bioactive molecules from extreme ecosystems with unique features, such as high temperatures. In this study, an innovative combination of function-driven screening of a compost metagenomic library and automatic extraction of halo areas with in-house MATLAB functions resulted in the identification of a promising clone with xylanase activity (LP4). The LP4 clone proved to be an effective xylanase producer under submerged fermentation conditions. Sequence and phylogenetic analyses revealed that the xylanase, Xyl4, corresponded to an endo-1,4-β-xylanase belonging to glycosyl hydrolase family 10 (GH10). When xyl4 was expressed in Escherichia coli BL21(DE3), the enzyme activity increased about 2-fold compared to the LP4 clone. To get insight on the interaction of the enzyme with the substrate and establish possible strategies to improve its activity, the structure of Xyl4 was predicted, refined, and docked with xylohexaose. Our data unveiled, for the first time, the relevance of the amino acids Glu133 and Glu238 for catalysis, and a close inspection of the catalytic site suggested that the replacement of Phe316 by a bulkier Trp may improve Xyl4 activity. Our current findings contribute to enhancing the catalytic performance of Xyl4 towards industrial applications.Key points• A GH10 endo-1,4-β-xylanase (Xyl4) was isolated from a compost metagenomic library• MATLAB’s in-house functions were developed to identify the xylanase-producing clones• Computational analysis showed that Glu133 and Glu238 are crucial residues for catalysisGraphical abstract

Integrating multi-platform assembly to recover MAGs from hot spring biofilms: insights into microbial diversity, biofilm formation, and carbohydrate degradation

BackgroundHot spring biofilms provide a window into the survival strategies of microbial communities in extreme environments and offer potential for biotechnological applications. This study focused on green and brown biofilms thriving on submerged plant litter within the Sungai Klah hot spring in Malaysia, characterised by temperatures of 58–74 °C. Using Illumina shotgun metagenomics and Nanopore ligation sequencing, we investigated the microbial diversity and functional potential of metagenome-assembled genomes (MAGs) with specific focus on biofilm formation, heat stress response, and carbohydrate catabolism.ResultsLeveraging the power of both Illumina short-reads and Nanopore long-reads, we employed an Illumina-Nanopore hybrid assembly approach to construct MAGs with enhanced quality. The dereplication process, facilitated by the dRep tool, validated the efficiency of the hybrid assembly, yielding MAGs that reflected the intricate microbial diversity of these extreme ecosystems. The comprehensive analysis of these MAGs uncovered intriguing insights into the survival strategies of thermophilic taxa in the hot spring biofilms. Moreover, we examined the plant litter degradation potential within the biofilms, shedding light on the participation of diverse microbial taxa in the breakdown of starch, cellulose, and hemicellulose. We highlight that Chloroflexota and Armatimonadota MAGs exhibited a wide array of glycosyl hydrolases targeting various carbohydrate substrates, underscoring their metabolic versatility in utilisation of carbohydrates at elevated temperatures.ConclusionsThis study advances understanding of microbial ecology on plant litter under elevated temperature by revealing the functional adaptation of MAGs from hot spring biofilms. In addition, our findings highlight potential for biotechnology application through identification of thermophilic lignocellulose-degrading enzymes. By demonstrating the efficiency of hybrid assembly utilising Illumina-Nanopore reads, we highlight the value of combining multiple sequencing methods for a more thorough exploration of complex microbial communities.

Diversity of culturable fungi in six Tibetan Plateau lakes, with descriptions of eight new taxa

ABSTRACT The combination of low temperatures, oligotrophic conditions, high altitude, and varying salinity in Tibetan Plateau lakes endows them with a wealth of distinctive fungal resources. This study aimed to investigate the diversity of culturable fungi in sediment and water samples collected from six lakes located on the Tibetan Plateau at elevations above 4,500 m. A total of 843 fungal strains were isolated by dilution plate method using four different media. Initial ITS analyses revealed that they belong to 156 species across 83 genera, spanning 50 families, 26 orders, 12 classes, and 6 phyla. Further morphological and multi-locus phylogenetic analyses were conducted, resulting in the formal descriptions of a new genus, Xizangia, and seven new species, including Alternaria xizangensis, Emericellopsis ovoidea, Myceliophthora xizangica, Preussia cylindricalis, Preussia sedimenticola, Pseudeurotium sedimenticola, and Xizangia sedimenticola. This research provides insights into the biodiversity of culturable fungi in the unique and extreme ecosystem, shedding light on the potential discovery of novel species and genera.

A sulfated exopolysaccharide derived from Chlorella sp. exhibiting in vitro anti-α-D-Glucosidase activity.

There is a great scientific curiosity to discover all environments sheltering microalgae, especially those with exceptional characteristics from coldest to hottest ones, the purpose remains to explore the potential of the native microalgae flora and the research for new bioactive compounds. This study aimed to isolate a polysaccharide-producing microalga from an extreme ecosystem and to evaluate its capacity to inhibit the α-D-glucosidase enzyme. Chlorella strain is isolated from hypersaline Lake in the Algerian desert. The exopolysaccharide extraction was performed by the concentration of free-cell supernatant in a rotary evaporator. The infrared analysis showed a characteristic footprint of carbohydrates with particular functional groups, such as sulfate. Gas chromatography-mass spectrometry has revealed a hetero-exopolysaccharide composed of galactose 35.75%, glucose 21.13%, xylose 16.81%, fructose 6.96%, arabinose 5.10%, and glucuronic acid 2.68%. The evaluation of the anti-hyperglycemic activity demonstrated a significant α-D-glucosidase inhibition of 80.94 ± 0.01% at 10mgmL-1 with IC50 equal to 4.31 ± 0.20mgmL-1. This study opens a vast prospect to use exopolysaccharides as natural nutraceutical or food additive.

Hidden Treasure: Halophilic Fungi as a Repository of Bioactive Lead Compounds.

The pressing demand for novel compounds to address contemporary health challenges has prompted researchers to venture into uncharted territory, including extreme ecosystems, in search of new natural pharmaceuticals. Fungi capable of tolerating extreme conditions, known as extremophilic fungi, have garnered attention for their ability to produce unique secondary metabolites crucial for defense and communication, some of which exhibit promising clinical significance. Among these, halophilic fungi thriving in high-salinity environments have particularly piqued interest for their production of bioactive molecules. This review highlights the recent discoveries regarding novel compounds from halotolerant fungal strains isolated from various saline habitats. From diverse fungal species including Aspergillus, Penicillium, Alternaria, Myrothecium, and Cladosporium, a plethora of intriguing molecules have been elucidated, showcasing diverse chemical structures and bioactivity. These compounds exhibit cytotoxicity against cancer cell lines such as A549, HL60, and K-562, antimicrobial activity against pathogens like Escherichia coli, Bacillus subtilis, and Candida albicans, as well as radical-scavenging properties. Notable examples include variecolorins, sclerotides, alternarosides, and chrysogesides, among others. Additionally, several compounds display unique structural motifs, such as spiro-anthronopyranoid diketopiperazines and pentacyclic triterpenoids. The results emphasize the significant promise of halotolerant fungi in providing bioactive compounds for pharmaceutical, agricultural, and biotechnological uses. However, despite their potential, halophilic fungi are still largely unexplored as sources of valuable compounds.

Chemical, biochemical, and bioactivity studies on some soda lakes, Wadi El-Natrun, Egypt

Wadi El-Natrun is one of the most observable geomorphological features in the North-Western Desert of Egypt; it contains several old saline and saline soda lakes. This study investigates physicochemical and biochemical characteristics and estimates the total phenolic content (TPC), total flavonoid content (TVC), and bioactivities of sediment, cyanobacteria, and brine shrimp (Artemia salina) in soda lakes, i.e., El-Hamra Lake 1 (H1) and El-Hamra Lake 2 (H2). These soda lakes are unique extreme ecosystems characterized by high pH (> 9.3), high alkalinity, and salinity. Some extremophilic microorganisms are hosted in this ecosystem. The results revealed that the chemical water type of studied lakes is soda-saline lakes according to the calculated percentage sequence of major cations and anions. Sodium ranked first among major cations with an abundance ratio of e% 58, while chloride came first among anions with an abundance ratio of e% 71, and bicarbonate and carbonate occupied the last rank with an abundance of 6%. The biochemical investigations showed that TPC and TVC are present in concern contents of sediment, cyanobacteria, and brine shrimp (A. salina) which contribute 89% of antioxidant capacity and antimicrobial activities. Thus, this study helps better understand the chemical and biochemical adaptations in soda lake ecosystems and explores natural sources with potential applications in antioxidant-rich products and environmental conservation efforts.

Spatio-temporal variations in the mesozooplankton assemblages off Clarence Island, Magellan Strait, Chile

The seasonality in the light regime from subpolar regions impinges on limitations in the zooplankton dynamics. However, knowledge about seasonal variations in the mesozooplankton assemblages is limited in the southern tip of South America and around the Magellan Strait. Here, we studied the seasonal variation (summer vs. winter) and the spatial distribution (dozens of kilometers) of the mesozooplankton on the occidental shore of Clarence Island, Magellan Strait, Chilean Patagonia. A total of 69 taxonomic groups were identified in the samples, varying from 65 in summer (early March 2020) to 50 in winter (June 2020). Copepods numerically dominated the plankton, particularly Drepanopus forcipatus and Clausocalanus brevipes, although chaetognaths were also abundant in winter. The similarity in the composition was higher for samples collected in summer, whereas in winter there was larger variability in the zooplankton structure. At spatial scale, a large sound at the eastern coast of the island, Dyneley sound showed different composition of copepods compared to other channels both in summer and winter. Seasonal variation was five times larger than the spatial variation in the similarity of the mesozooplankton composition. Finally, higher richness and lower evenness were detected in austral summer, while the opposite was noticed in winter, with differences in alpha-diversity indices between seasons but not among locations. Understanding the drivers of seasonal variability in the zooplankton composition of this extreme ecosystem is essential for predictions of the impacts of salmon farming and climate change in southern Patagonia.

Exploring the prokaryote-eukaryote interplay in microbial mats from an Andean athalassohaline wetland.

Microbial community assembly results from the interaction between biotic and abiotic factors. However, environmental selection is thought to predominantly shape communities in extreme ecosystems. Salar de Huasco, situated in the high-altitude Andean Altiplano, represents a poly-extreme ecosystem displaying spatial gradients of physicochemical conditions. To disentangle the influence of abiotic and biotic factors, we studied prokaryotic and eukaryotic communities from microbial mats and underlying sediments across contrasting areas of this athalassohaline ecosystem. The prokaryotic communities were primarily composed of bacteria, notably including a significant proportion of photosynthetic organisms like Cyanobacteria and anoxygenic photosynthetic members of Alpha- and Gammaproteobacteria and Chloroflexi. Additionally, Bacteroidetes, Verrucomicrobia, and Deltaproteobacteria were abundantly represented. Among eukaryotes, photosynthetic organisms (Ochrophyta and Archaeplastida) were predominant, alongside relatively abundant ciliates, cercozoans, and flagellated fungi. Salinity emerged as a key driver for the assembly of prokaryotic communities. Collectively, abiotic factors influenced both prokaryotic and eukaryotic communities, particularly those of algae. However, prokaryotic communities strongly correlated with photosynthetic eukaryotes, suggesting a pivotal role of biotic interactions in shaping these communities. Co-occurrence networks suggested potential interactions between different organisms, such as diatoms with specific photosynthetic and heterotrophic bacteria or with protist predators, indicating influences beyond environmental selection. While some associations may be explained by environmental preferences, the robust biotic correlations, alongside insights from other ecosystems and experimental studies, suggest that symbiotic and trophic interactions significantly shape microbial mat and sediment microbial communities in this athalassohaline ecosystem.IMPORTANCEHow biotic and abiotic factors influence microbial community assembly is still poorly defined. Here, we explore their influence on prokaryotic and eukaryotic community assembly within microbial mats and sediments of an Andean high-altitude polyextreme wetland system. We show that, in addition to abiotic elements, mutual interactions exist between prokaryotic and eukaryotic communities. Notably, photosynthetic eukaryotes exhibit a strong correlation with prokaryotic communities, specifically diatoms with certain bacteria and other protists. Our findings underscore the significance of biotic interactions in community assembly and emphasize the necessity of considering the complete microbial community.

On the distribution and habitat use of the sub-Antarctic fly Hyadesimyia clausa Bigot (Diptera, Tachinidae) according to citizen science.

Hyadesimyia clausa Bigot is a morphologically striking tachinid that inhabits the Sub-Antarctic Ecoregion of the Magallanes Region in Chile and Tierra del Fuego province in Argentina. Much of the distributional information about this species is restricted to the Cape Horn islands, which have extreme environmental conditions, but the species' natural history, range limits, and habitat use have never been described or confirmed. Our goals were to describe the distributional limits of this sub-Antarctic fly with the help of citizen science and use this information type to describe this tachinid's habitat use and potential biological interactions with nonvascular and vascular flora. We found that citizen science significantly increased our understanding of the extent of occurrence, expanding the known distributional range by 195 km to the north and 153 km to the west. On the contrary, the values for the area of occupancy were not significant, but the occupancy overlap between different records was very low. We confirmed that H. clausa's habitat uses peatlands and although we have not provided evidence of pollination or movement of spores, we hypothesized, that the walking activity of H. clausa could help move sperm from mosses and pollen from the flowers of vascular plants, so they could act as potential pollinators. Citizen science can reduce and eliminate some scientific knowledge shortfalls and propose new ecological questions that could increase our knowledge of extreme ecosystems.

Multi-omics insights into biogeochemical responses to organic matter addition in an acidic pit lake: Implications for bioremediation

Acidic pit lakes (APLs) emerge as reservoirs of acid mine drainage in flooded open-pit mines, representing extreme ecosystems and environmental challenges worldwide. The bioremediation of these oligotrophic waters necessitates the addition of organic matter, but the biogeochemical response of APLs to exogenous organic matter remains inadequately comprehended. This study delves into the biogeochemical impacts and remediation effects of digestate-derived organic matter within an APL, employing a multi-omics approach encompassing geochemical analyses, amplicon and metagenome sequencing, and ultra-high resolution mass spectrometry. The results indicated that digestate addition first stimulated fungal proliferation, particularly Ascomycetes and Basidiomycetes, which generated organic acids through lignocellulosic hydrolysis and fermentation. These simple compounds further supported heterotrophic growth, including Acidiphilium, Acidithrix, and Clostridium, thereby facilitating nitrate, iron, and sulfate reduction linked with acidity consumption. Nutrients derived from digestate also promoted the macroscopic development of acidophilic algae. Notably, the increased sulfate reduction-related genes primarily originated from assimilatory metabolism, thus connecting sulfate decrease to organosulfur increase. Assimilatory and dissimilatory sulfate reduction collectively contributed to sulfate removal and metal fixation. These findings yield multi-omics insights into APL biogeochemical responses to organic matter addition, enhancing the understanding of carbon-centered biogeochemical cycling in extreme ecosystems and guiding organic amendment-based bioremediation in oligotrophic polluted environments.