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Genome-resolved assessment of archaeal diversity in full-scale anaerobic digesters reveals variability in mcrA primer coverage.

AIMS: Methanogenic archaea are key players in anaerobic digestion, driving methane production in biogas reactors. This study aimed to assess the diversity of methanogenic archaea in full-scale anaerobic digesters using genome-resolved metagenomics and to systematically evaluate the taxonomic coverage of commonly used mcrA-targeted qPCR primer sets against this genomic framework. METHODS AND RESULTS: Methanogenic diversity was assessed using 113 dereplicated archaeal metagenome-assembled genomes (MAGs) recovered from 109 full-scale anaerobic digesters treating diverse substrates. Genome-resolved analyses revealed a diverse archaeal community spanning multiple phyla, dominated by Halobacteriota and Methanobacteriota, with additional representatives from Methanobacteriota_B, Thermoplasmatota, and Thermoproteota. The presence of the mcrA gene was identified in a subset 55 MAGs, which were subsequently used as the genomic framework to evaluate six commonly used mcrA qPCR primer sets in silico. This subset clustered into nine phylogenetic groups and formed the basis for the primer coverage analysis. The evaluation revealed marked differences in taxonomic coverage among primer sets. Most primers preferentially detected Methanobacteriales and Methanosarcinales, while underrepresenting or excluding other methanogenic lineages, including H₂-dependent methylotrophic Methanomassiliicoccaceae. CONCLUSIONS: Commonly used mcrA primer sets differ substantially in their ability to capture methanogenic diversity, with some showing broad representation of reactor-associated methanogens and others exhibiting strong lineage-specific biases. Genome-resolved metagenomics provides an effective framework for benchmarking primer performance and supports the selection and improvement of molecular tools for more accurate monitoring of anaerobic digestion systems.

Archaea

Ori-Finder-Arch: An Updated Web Server for the Annotation and Visualization of Archaeal Replication Origins.

Archaea are promising chassis organisms in biotechnology, and the accurate annotation of their chromosomal replication origins (oriCs) is the key to unlocking their full potential. However, the existing Ori-Finder 2 web server suffers from low accuracy, slow speed, and limited scalability. In this study, we present Ori-Finder-Arch, an updated web server for high-performance oriC prediction in archaea. This pipeline integrates HMMER-based replication initiation protein (RIP) annotation, refined consensus motif recognition, and GC profile-based DNA unwinding element (DUE) detection. On a benchmark set of experimentally validated oriCs, Ori-Finder-Arch achieved a recall of 95.6% and a precision of 86.0%, substantially outperforming Ori-Finder 2 (62.2% and 63.6%, respectively), while running 4.75 times faster and supporting diverse assembly levels. When applied to the available archaeal assemblies, it successfully annotated 17,472 oriCs. Meanwhile, the web server provides interactive visualizations at different levels. In conclusion, Ori-Finder-Arch offers an efficient, accurate, and user-friendly platform for advanced studies of archaeal DNA replication initiation and synthetic biology applications, and is freely available at https://tubic.org/Ori-Finder-Arch/ and https://tubic.tju.edu.cn/Ori-Finder-Arch/.

Archaea

The Expanding Histone Universe: Histone-Based DNA Organization in Noneukaryotic Organisms.

Histones are small basic proteins that form the proteinaceous core of the nucleosome, the repeating building block of chromatin in all eukaryotes. Long thought to be exclusive to eukaryotes, histones are now increasingly appreciated for their roles in organizing genomes across all domains of life, namely in archaea, bacteria, and even viruses. We survey recent advances in our understanding of the imaginative uses of histones in disparate biological entities, ranging from nucleosome-like metastable particles in giant viruses to slinky-like hypernucleosomes in archaea to bacterial histones that bind DNA in decidedly unorthodox ways. Across these different contexts, we examine how DNA compaction and conformation emanate from evolutionarily conserved aspects of histone structure, including how the oligomeric states of histones dictate their capacity to contort DNA in different conformations. It appears that relatively small tweaks to the amino acid sequences of histones can result in structural and functional variations in DNA binding. As such, nucleosomes in eukaryotes sample only a narrow range of possible structures.

Histones

Unveiling microbial communities and biogeochemical cycles in Antarctic colored snow.

Snow cover, the extensive terrestrial habitat in Antarctica, sometimes exhibits vivid coloration, yet the structure and function of its microbial communities remain poorly characterized. Using metagenomic sequencing of red snow (RS) and green snow (GS) from the Fildes Peninsula, we found that bacterial, eukaryotic, and archaeal relative abundances were 85.82%, 13.52% and 0.16%, respectively. &#x3b2;-Diversity differed significantly between RS and GS across these three domains (P&#x2009;<&#x2009;0.05). Dominant bacterial phyla included Bacteroidota (RS: 62.61%; GS: 38.72%) and Pseudomonadota (RS: 32.80%; GS: 54.10%). Among eukaryotes, Chlorophyta (RS: 58.10%; GS: 52.98%) and Basidiomycota (RS: 14.80%; GS: 8.08%) were prevalent. Nanobdellota dominated archaea, with lower abundance in RS than GS. In the algal community, Sanguina, Gonium and Chloromonas were significantly enriched in red snow, while Chlorella and Micractinium were enriched in green snow (P&#x2009;<&#x2009;0.05). Marker genes associated with carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) cycles were identified in green and red snow. Aerobic respiration and phosphate regulation were significantly enriched in red snow, while CO oxidation, fermentation, and denitrification were significantly enriched in green snow. Key microbial genera associated with these functional pathways also varied. In the denitrification of red snow, Stutzerimonas was the most abundant genus, while Janthinobacterium was abundant in green snow. Nitrification-related genes were detected only in red snow based on the present metagenomic data. The network of the red snow microbial community was potentially more complex and resistant based on topology, which not only benefited its own long-term survival but might also have potentially influenced the positive feedback effect of snowmelt by maintaining a low-albedo snow surface. This provided an ecological implication under climate warming: the expansion of red snow patches showed the potential to the increase nitrate runoff export, which would affect nitrogen nutrient levels in coastal Antarctic waters. Overall, this study used metagenomics to compare the multidomain (bacteria, archaea and eukaryotes) composition and diversity between red snow and green snow, and directly linked key microbial taxa with functional genes of biogeochemical cycles. This study provided new insights into the biological characteristics and functional potential of Antarctic colored snow.

Snow

CRISPR-based gene knockout in the model haloarchaeon Haloferax mediterranei.

Halophilic archaea, a specialized group of extremophiles that inhabit hypersaline environments, exhibit distinctive physiological and metabolic features. Traditional genetic manipulation of these organisms, predominantly reliant on homologous recombination techniques, suffers from limitations such as complex procedures and extended timelines, which hinder functional genomics research and the development of practical applications. This study established a CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-mediated gene knockout system in the model halophilic archaeon Haloferax mediterranei. A polyethylene glycol (PEG)-mediated transformation method was used to deliver a plasmid carrying a mini-CRISPR array into H. mediterranei. The crtB gene, involved in pigment synthesis, was successfully knocked out, demonstrating the feasibility of CRISPR-based editing in H. mediterranei. To further validate the reliability and targeting accuracy of the system, the hlyR4 gene, encoding an extracellular serine protease, was also disrupted. The CRISPR-mediated gene knockout efficiency for hlyR4 reached 27%, significantly higher than the approximately 3% efficiency achieved with conventional homologous recombination. The establishment of this CRISPR-based gene knockout system provides a more efficient genetic tool for H. mediterranei and lays a new experimental foundation for exploiting microbial resources from extreme environments. In this study, H. mediterranei was selected as the model organism for haloarchaea. For the first time, we successfully constructed a CRISPR-based gene knockout system in a model halophilic archaeon. This system provides a solution for CRISPR-based gene knockout tools, which are currently unavailable in model halophilic archaea, and offers an effective tool for functional genomics studies in extremophiles.

Haloferax mediterranei

Up-to-date, and taxonomy-curated mcrA reference databases for methanogen community profiling.

The methyl-coenzyme M reductase subunit alpha gene (mcrA) is an important phylogenetic marker for high throughput ecological profiling of methanogenic archaea, central to industrial biological methane production and greenhouse gas emissions. Yet, dedicated reference databases predate current relevant NCBI sequence accumulation and archaeal taxonomic revision. We present three updated mcrA reference databases: (i) one derived from NCBI-catalogued methanogen genomes (1572 sequences); (ii) a database built by expansion of a previously published reference dataset, leveraging the NCBI nucleotide collection (27,942 sequences); (iii) a curated-taxonomy version of the latter. The updated amplicon databases provide a&#xa0;&#x223c;&#xa0;3.5-fold sequence richness expansion, extend genus-level richness from 31 to 83 taxa, more than 4-fold species-level richness, and incorporate novel lineages compared with the previous reference dataset (e.g. Thermoplasmatota-encompassed). All databases were formatted to support analysis with relevant contemporary software pipelines and packages. Overall, the generated databases facilitate a highly improved characterization of methanogen diversity and ecology.

Archaea

Hypoosmolarity inhibits ammonia oxidation by terrestrial and freshwater Nitrosopumilaceae members.

Salinity strongly influences the physiology and distribution of nitrifying microorganisms, yet the effects of low salinity remain understudied. This study investigates the impact of hypoosmolarity on different groups of ammonia oxidizers in soil and freshwater reservoirs, as well as in pure culture isolates. In soil microcosms amended with ammonium, at low salinity levels (~120&#xa0;&#x3bc;S/cm), comparable to values commonly found in pristine terrestrial and freshwater environments, the abundance of ammonia-oxidizing bacteria (AOB), dominated by Nitrosomonas oligotropha, significantly increased. In contrast, the growth of ammonia-oxidizing archaea (AOA), dominated by "Candidatus Nitrosotenuis" of the Nitrosopumilaceae family, was stimulated by high salinity (~760&#xa0;&#x3bc;S/cm). In ammonium-fed freshwater microcosms, the abundance of AOB, dominated by N. oligotropha, significantly increased under both low (~170&#xa0;&#x3bc;S/cm) and high salinity (~850&#xa0;&#x3bc;S/cm) conditions. In the presence of allylthiourea (50&#xa0;&#x3bc;M), used to inhibit bacterial ammonia oxidation, AOA were sensitive to low salinity in both soil and freshwater microcosms. Consistently, culture-dependent studies revealed marked growth inhibition of terrestrial AOA, especially members of Nitrosopumilaceae, under hypoosmolarity, unlike AOB and complete ammonia oxidizer (comammox) strains. Genomic analyses, along with transcriptomic studies, suggested that the sensitivity of AOA to hypoosmolarity stress was possibly due to a lack of osmoregulatory transport systems and their S-layer cell wall structure. Overall, this study indicates hypoosmolarity as an important factor shaping the ecological niches and distribution of ammonia oxidizers, as well as nitrification activities, in terrestrial and freshwater environments that are increasingly affected by intensified water cycles due to global change.

Ammonia

Potential survival strategies of novel comammox and nitrite-oxidizing Nitrospira synthesizing osmoprotectants in a wastewater microbiome treating high-ammonia brackish landfill leachate.

BACKGROUND: In the late stages of landfill operation, leachate becomes brackish and contains high concentrations of ammonia with limited organic carbon. At leachate treatment facilities, it is typically subjected to nitrification followed by denitrification, with methanol supplied as an external electron donor. This unique environment may harbor novel microorganisms, including nitrifiers. Although a variety of microorganisms are involved in nitrification, their substrate specificity and salinity tolerance remain insufficiently understood. In this study, a genome-centric metagenome analysis was conducted on the microbiome from a leachate treatment facility at a closed landfill. RESULTS: A total of 68 metagenome-assembled genomes (MAGs) were reconstructed, including 64 putative novel species. Among these, two Nitrospira MAGs were recovered: a novel complete ammonia-oxidizing bacterium (comammox), Nitrospira LAS72 (88.72% completeness, 2.10% contamination), and canonical nitrite-oxidizing Nitrospira LAS18 (99.98% completeness, 2.29% contamination). Comparative genomic analysis with 260 publicly available Nitrospira genomes revealed that LAS18 represents a new sub-lineage within lineage VII of the Nitrospira genus. Two ammonia-oxidizing archaea (AOA), Candidatus Nitrosocosmicus LAS21 and Nitrosarchaeum LAS73, were also identified, while canonical ammonia-oxidizing bacteria were not detected. Given the brackish conditions (1.23% salinity) and the methanol-fed operation of the treatment facility, the genomic potential for osmotic stress adaptation and methanol metabolism was investigated. Comammox Nitrospira LAS72 harbors biosynthetic pathways for several compatible solutes (osmoprotectants), including glycine betaine, proline, trehalose, and L-glutamate. Moreover, comammox Nitrospira LAS72 possesses genetic potential for oxidizing formaldehyde, suggesting that it may exploit these methanol-derived intermediates as energy sources. These features indicate that LAS72 may withstand osmotic fluctuations through the production of various osmoprotectants and thrive under the unique conditions of a methanol-fed environment. CONCLUSIONS: The discovery of novel comammox Nitrospira and canonical Nitrospira forming a new sub-lineage within lineage VII of the Nitrospira genus in an ammonia-rich brackish environment provides the first genomic evidence for evolutionary adaptation among nitrifiers to saline, methanol-fed environments. These findings enhance our understanding of the ecological and evolutionary dynamics shaping nitrifier communities in complex treatment ecosystems. Video Abstract.

Ammonia

Metagenomic Insights Into Microbial Diversity of Tea Rhizosphere of the Kangra Valley.

This study provides the first metagenomic assessment of microbial diversity from the tea rhizosphere of the Kangra valley. Tea rhizosphere soil samples were collected from 4 locations (Dharamshala, Baijnath, Palampur, and Joginder Nagar) of the Kangra valley. DNA extracts of rhizosphere samples were analysed for bacterial and Archaeal diversity using amplicon sequencing (V3-V4) region of the 16S rRNA gene and Fungal diversity using ITS1 and ITS2 regions. Baijnath and Palampur samples showed the highest bacterial richness, while Dharamshala and Palampur had the highest fungal richness. Proteobacteria was a dominant phylum in all the rhizosphere samples, followed by Firmicutes, Actinobacteria, Acidobacteria, and Bacteroidetes. A total of 11 fungal phyla were identified among all the locations, with abundance of Ascomycota and Basidiomycota. For the Archaea domain, uncultured archaeon and Aeropyrum camini were the most common found among all the locations. A small fraction (<&#x2009;0.5%) of Bacillus and Pseudomonas species were observed among all the locations. Alpha and beta diversity indices displayed notable differences within and between microbial diversities. Soil factors were variably associated with microbial diversity, with nitrogen positively aligned with fungal diversity, while EC and K were associated with Archaeal diversity. Soil pH and OM% showed moderate associations with bacterial diversity. These findings provided valuable and comprehensive insights into tea rhizosphere microbial ecology and could be used to better understand microbial functions and their role in plant health.

Rhizosphere

NusG-Spt5 Transcription Factors: Universal, Dynamic Modulators of Gene Expression.

The accurate and efficient biogenesis of RNA by cellular RNA polymerase (RNAP) requires accessory factors that regulate the initiation, elongation, and termination of transcription. Of the many discovered to date, the elongation regulator NusG-Spt5 is the only universally conserved transcription factor. With orthologs and paralogs found in all three domains of life, this ubiquity underscores their ancient and essential regulatory functions. NusG-Spt5 proteins evolved to maintain a similar binding interface to RNAP through contacts of the NusG N-terminal domain (NGN) that bridge the main DNA-binding cleft. We propose that varying strength of these contacts, modulated by tethering interactions, either decrease transcriptional pausing by smoothing the rugged thermodynamic landscape of transcript elongation or enhance pausing, depending on which conformation of RNAP is stabilized by NGN contacts. NusG-Spt5 contains one (in bacteria and archaea) or more (in eukaryotes) C-terminal domains that use a KOW fold to contact diverse targets, tether the NGN, and control RNA biogenesis. Recent work highlights these diverse functions in different organisms. Some bacteria contain multiple specialized NusG paralogs that regulate subsets of operons via sequence-specific targeting, controlling production of antibiotics, toxins, or capsule proteins. Despite their common origin, NusG orthologs can differ in their target selection, interacting partners, and effects on RNA synthesis. We describe the current understanding of NusG-Spt5 structure, interactions with RNAP and other regulators, and cellular functions including significant recent progress from genome-wide analyses, single-molecule visualization, and cryo-EM. The recent findings highlight the remarkable diversity of function among these structurally conserved proteins.

Archaea

Unraveling the coastal marine plastisphere archaeome.

Plastic pollution has created an expanding anthropogenic microbial niche, the plastisphere, raising questions about microbial ecology and associated impacts. Archaea, the third domain of life with fundamental ecological and evolutionary significance, remain poorly understood in this habitat. Here, using paired plastic debris and bulk-water samples from coastal marine ecosystems, key archaeal habitats increasingly threatened by plastic pollution, we characterize the plastisphere archaeome through archaeal amplicon sequencing and metagenomics. We show that the archaeome is significantly reshaped in the plastisphere, exhibiting higher taxonomic diversity, greater community heterogeneity, and selective enrichment of Euryarchaeota and Crenarchaeota. Archaeal genes involved in methane, nitrogen, and sulfur cycling are enriched in the plastisphere. Taxonomic and functional divergence between the plastisphere and bulk water increases with anthropogenic chemical stress. These findings suggest that plastic pollution could alter marine archaeal diversity, biogeography, and biogeochemical potential, extending understanding of plastisphere impacts to the archaeal domain.

Archaea

Structural basis for pre-tRNA recognition and processing by the human tRNA splicing endonuclease complex.

Throughout bacteria, archaea and eukarya, certain tRNA transcripts contain introns. Pre-tRNAs with introns require splicing to form the mature anticodon stem loop. In eukaryotes, tRNA splicing is initiated by the heterotetrameric tRNA splicing endonuclease (TSEN) complex. All TSEN subunits are essential, and mutations within the complex are associated with a family of neurodevelopmental disorders known as pontocerebellar hypoplasia (PCH). Here, we report cryo-electron microscopy structures of the human TSEN-pre-tRNA complex. These structures reveal the overall architecture of the complex and the extensive tRNA binding interfaces. The structures share homology with archaeal TSENs but contain additional features important for pre-tRNA recognition. The TSEN54 subunit functions as a pivotal scaffold for the pre-tRNA and the two endonuclease subunits. Finally, the TSEN structures enable visualization of the molecular environments of PCH-causing missense mutations, providing insight into the mechanism of pre-tRNA splicing and PCH.

Humans

A compendium of horizontal gene transfers in Metazoa.

With more eukaryotic genomes available for study researchers have been able to identify a growing number of horizontal gene transfer (HGT) candidates. We compiled 9,495 protein coding genes that were identified as horizontally transferred to metazoan hosts in the published literature. This dataset contains gene transfers from bacteria, fungi, archaea and protists to metazoans. We assigned a confidence score to each gene based on the methods used in the scientific paper reporting HGT. All the coding sequences and protein sequences for the HGT genes are stored in a fig share repository. This dataset can be used to identify trends in genome and protein evolution and provide a foundation for creating a centralized HGT database for eukaryotes.

Gene Transfer, Horizontal

Unraveling the diversity, function, and virus-host interactions of archaeal proviruses.

Archaea, the third domain of life, play critical roles in global biogeochemical cycles. However, archaeal proviruses integrated into host genomes remain largely unexplored. To bridge this gap, we conducted a large-scale mining of genomes spanning all presently known 21 archaeal phyla for their proviruses. We identified 770 archaeal proviruses across 12 archaeal phyla and 84 families, which clustered into 655 viral operational taxonomic units (vOTUs). Among these, 86.1% of the vOTUs were novel at the species level, and 69.3% could not be classified at the family level, substantially expanding the known diversity of archaeal viruses. Additionally, phylogenomic analysis supported the proposal of 16 putative novel viral families, further extending the current taxonomy landscape of archaeal viruses. Notably, 21.8% of the identified proviruses were predicted to adopt a lytic lifestyle, suggesting that these proviruses may retain the capacity to enter the lytic cycle under appropriate conditions. Host prediction indicated only 14 out of the 655 vOTUs might have potential across-lineage infection abilities. We detected 63 anti-defense genes encoded by 61 provirus genomes, such as anti-CRISPR and anti-RM, suggesting an ongoing evolutionary arms race between hosts and proviruses. However, only 10 auxiliary metabolic genes (AMGs) were identified, suggesting a limited impact of proviruses in the modulation of host metabolism through AMGs. This study establishes a systematic global genomic atlas of archaeal proviruses, advancing our understanding of their distribution and diversity while providing a foundation for future research into how proviruses regulate archaeal metabolism and ecosystem functioning.

anti-defense system

Viral communities from long-term anaerobic alkane-oxidizing enrichment cultures encode predicted cell surface adhesion functions.

The anaerobic oxidation of methane and C2+-alkanes is a dominant metabolism within hydrocarbon-rich deep-sea sediments and is largely mediated by alkane-oxidizing archaea in metabolic partnership with syntrophic sulfate-reducing bacteria. Although these processes fuel a diverse ecosystem, the viral component of alkane-rich sediments has historically been overlooked. We analyzed the viral assemblages in long-term sediment-free cultures of alkane-degrading organisms and found that abiotic factors such as incubation temperature had a greater correlation with community composition than with the phylogenetic patterns among individual viral species. No auxiliary metabolic genes (AMGs) directly involved in hydrocarbon oxidation or sulfate reduction were found, but the presence of candidate AMGs involved in heme synthesis pathways common in methane oxidizers hints at a possible viral impact on alkane degradation. We also examined potential host-virus pairs using CRISPR- and tRNA-based methods. Lastly, we identified the presence of nosD-like proteins in viruses from sediment-derived systems that are not present in water column datasets; their distribution, genomic context, and lack of canonical nosD characteristics suggest an alternate adhesion-related role in sediment communities. The number of new viruses obtained from these multi-year enrichment cultures and their potential roles in mediating host physiology illustrate the importance of studying the viral component in laboratory and environmental systems.

Geologic Sediments

Identification, characterization and classification of prokaryotic nucleoid-associated proteins.

Common throughout life is the need to compact and organize the genome. Possible mechanisms involved in this process include supercoiling, phase separation, charge neutralization, macromolecular crowding, and nucleoid-associated proteins (NAPs). NAPs are special in that they can organize the genome at multiple length scales, and thus are often considered as the architects of the genome. NAPs shape the genome by either bending DNA, wrapping DNA, bridging DNA, or forming nucleoprotein filaments on the DNA. In this mini-review, we discuss recent advancements of unique NAPs with differing architectural properties across the tree of life, including NAPs from bacteria, archaea, and viruses. To help the characterization of NAPs from the ever-increasing number of metagenomes, we recommend a set of cheap and simple in&#xa0;vitro biochemical assays that give unambiguous insights into the architectural properties of NAPs. Finally, we highlight and showcase the usefulness of AlphaFold in the characterization of novel NAPs.

Archaea

Large-scale benchmarking of prokaryotic annotation tools across thousands of species.

BACKGROUND: Genome annotation is an important step in deriving functional meaning from prokaryotic sequencing data, yet systematic evaluations guiding tool selection are lacking. We present the first large-scale investigation of four prominent open-source annotation tools (Prokka, Bakta, EggNOG-mapper, and PGAP) across 156,033 diverse genomes. This includes Escherichia coli strains for baseline performance, thousands of archaea and bacteria genomes, as well as frameshifted and metagenome-assembled genomes. RESULTS: Bakta excels in annotating high-quality bacterial genomes, while PGAP was better for archaeal genomes and challenging bacterial assemblies, including metagenome-assembled, fragmented, or contaminated samples. For Gene Ontology annotation, PGAP consistently provides broader term coverage, whereas EggNOG-mapper offers more terms per feature. CONCLUSIONS: Our findings highlight tool-specific strengths crucial for selecting optimal solutions based on genome quality, taxonomy, and origin (e.g. MAGs). This study provides an evidence-based guide for users and informs future tool development.

Molecular Sequence Annotation

Microbial decomposer diversity and metabolic function during the decomposition of brine shrimp carcasses in a saline lake.

BACKGROUND: Decomposition of brine shrimp carcasses has a crucial role in carbon cycling of saline lakes, yet the microbial dynamics remain poorly understood. RESULTS: Here we integrated metagenomics, metatranscriptomics, culturomics, metabolomics, and microcosm experiments to investigate microbial community succession and function during brine shrimp (Artemia sp.) carcass decomposition in Barkol Lake, a hypersaline lake in China. A total of 149 metagenome-assembled genomes (MAGs) and 77 pure culture genomes were recovered across 33 phyla, with 72.12% genomes representing species-level novel lineages. Our results reveal diverse bacterial and archaeal taxa, including novel lineages from CG03, T1Sed10-126 and rare archaeal taxa (Asgardarchaeota, Thermoplasmatota, Nanoarchaeota, and Halobacteriota), involved in degradation of biomacromolecules-proteins, carbohydrates, lipids, and nucleic acids-via extracellular hydrolysis, nutrient transport, and intracellular catabolism. These taxa exhibit substrate preferences, rapidly responding to the breakdown of polysaccharides and proteins, followed by lipids and nucleic acids. Hydrolyzed oligomers are further oxidized by various microbes through fermentation, sulfate reduction, and methanogenesis via metabolic handoffs. Additionally, viral auxiliary metabolic genes (AMGs) further enhance microbial host functions, contributing to key ecological processes such as carbon cycling and stress response. A temporally structured microbial decomposer network (MDN) was observed, driving mineralization cascades from fermentation to sulfate reduction and methanogenesis. CONCLUSIONS: This study reveals microbial metabolic handoffs and virus-mediated modulation as critical mechanisms for organic matter turnover, expanding the known diversity and function of decomposers in saline ecosystems. Our findings offer new insights into biogeochemical processes in saline lakes and highlight a synergistic microbial decomposer network involving bacteria, archaea, and viruses that collectively drive nutrient cycling during brine shrimp carcass decomposition. Video Abstract.

Animals