Viral Operational Taxonomic Units Research Articles

Time-series metaproteogenomics of a high-CO2 aquifer reveals active viruses with fluctuating abundances and broad host ranges

Abstract Ecosystems subject to mantle degassing are of particular interest for understanding global biogeochemistry, as their microbiomes are shaped by prolonged exposure to high CO2 and have recently been suggested to be highly active. While the genetic diversity of bacteria and archaea in these deep biosphere systems have been studied extensively, little is known about how viruses impact these microbial communities. Here, we show that the viral community in a high-CO2 cold-water geyser (Wallender Born, Germany) undergoes substantial fluctuations over a period of 12 days, although the corresponding prokaryotic community remains stable, indicating a newly observed “infect to keep in check” strategy that maintains prokaryotic community structure. We characterized the viral community using metagenomics and metaproteomics, revealing 8,654 viral operational taxonomic units (vOTUs). CRISPR spacer-to-protospacer matching linked 278 vOTUs to 32 hosts, with many vOTUs sharing hosts from different families. High levels of viral structural proteins present in the metaproteome (several structurally annotated based on AlphaFold models) indicate active virion production at the time of sampling. Viral genomes expressed many proteins involved in DNA metabolism and manipulation, and encoded for auxiliary metabolic genes, which likely bolster phosphate and sulfur metabolism of their hosts. The active viral community encodes genes to facilitate acquisition and transformation of host nutrients, and appears to consist of many nutrient-demanding members, based on abundant virion proteins. These findings indicate viruses are inextricably linked to the biogeochemical cycling in this high-CO2 environment and substantially contribute to prokaryotic community stability in the deep biosphere hotspots.

Characterizations of gut bacteriome, mycobiome, and virome of healthy individuals living in sea-level and high-altitude areas.

The contribution of gut microbiota to human high-altitude adaptation remains inadequatelyunderstood. Here a comparative analysis of gut microbiota was conducted between healthy individuals living at sealevel and high altitude using deep whole-metagenome shotgun sequencing, to investigate the adaptivemechanisms of gut microbiota in plateau inhabitants. The results showed the gut bacteriomes in high-altitude individuals exhibited greater within-samplediversity and significant alterations in both bacterial compositional and functional profiles when compared to thoseof sea-level individuals, indicating the potential selection of unique bacteria associated with high-altitudeenvironments. The strain-level investigation revealed enrichment of Collinsella aerofaciens and Akkermansiamuciniphila in high-altitude populations. The characteristics of gut virome and gut mycobiome were alsoinvestigated. Compared to sea-level subjects, high-altitude subjects exhibited a greater diversity in their gut virome,with an increased number of viral operational taxonomic units (vOTUs) and unique annotated genes. Finally,correlation analyses revealed 819 significant correlations between 42 bacterial species and 375 vOTUs, while nosignificant correlations were observed between bacteria and fungi or between fungi and viruses. The findings have significantly contributed to an enhanced comprehension of the mechanismsunderlying the high-altitude geographic adaptation of the human gut microbiota.

Developmental Dynamics of the Gut Virome in Tibetan Pigs at High Altitude: A Metagenomic Perspective across Age Groups.

Tibetan pig is a geographically isolated pig breed that inhabits high-altitude areas of the Qinghai-Tibetan plateau. At present, there is limited research on viral diseases in Tibetan pigs. This study provides a novel metagenomic exploration of the gut virome in Tibetan pigs (altitude ≈ 3000 m) across three critical developmental stages, including lactation, nursery, and fattening. The composition of viral communities in the Tibetan pig intestine, with a dominant presence of Microviridae phages observed across all stages of development, in combination with the previous literature, suggest that it may be associated with geographical locations with high altitude. Functional annotation of viral operational taxonomic units (vOTUs) highlights that, among the constantly increasing vOTUs groups, the adaptability of viruses to environmental stressors such as salt and heat indicates an evolutionary response to high-altitude conditions. It shows that the lactation group has more abundant viral auxiliary metabolic genes (vAMGs) than the nursery and fattening groups. During the nursery and fattening stages, this leaves only DNMT1 at a high level. which may be a contributing factor in promoting gut health. The study found that viruses preferentially adopt lytic lifestyles at all three developmental stages. These findings not only elucidate the dynamic interplay between the gut virome and host development, offering novel insights into the virome ecology of Tibetan pigs and their adaptation to high-altitude environments, but also provide a theoretical basis for further studies on pig production and epidemic prevention under extreme environmental conditions.

Airborne antibiotic resistome and microbiome in pharmaceutical factories

Antimicrobial resistance is considered to be one of the biggest public health problems, and airborne transmission is an important but under-appreciated pathway for the spread of antibiotic resistance genes (ARGs) in the environment. Previous research has shown pharmaceutical factories to be a major source of ARGs and antibiotic resistant bacteria (ARB) in the surrounding receiving water and soil environments. Pharmaceutical factories are hotspots of antibiotic resistance, but the atmospheric transmission and its environmental risk remain more concerns. Here, we conducted a metagenomic investigation into the airborne microbiome and resistome in three pharmaceutical factories in China. Soil (average: 38.45%) and wastewater (average: 28.53%) were major contributors of airborne resistome. ARGs (vanR/vanS, blaOXA, and CfxA) conferring resistance to critically important clinically used antibiotics were identified in the air samples. The wastewater treatment area had significantly higher relative abundances of ARGs (average: 0.64 copies/16S rRNA). Approximately 28.2% of the detected airborne ARGs were found to be associated with plasmids, and this increased to about 50% in the wastewater treatment area. We have compiled a list of high-risk airborne ARGs found in pharmaceutical factories. Moreover, A total of 1,043 viral operational taxonomic units were identified and linked to 47 family-group taxa. Different CRISPR-Cas immune systems have been identified in bacterial hosts in response to phage infection. Similarly, higher phage abundance (average: 2451.70 PPM) was found in the air of the wastewater treatment area. Our data provide insights into the antibiotic resistance gene profiles and microbiome (bacterial and non-bacterial) in pharmaceutical factories and reveal the potential role of horizontal transfer in the spread of airborne ARGs, with implications for human and animal health.

Temporal Dynamics and Contribution of Phage Community to the Prevalence of Antibiotic Resistance Genes in a Full-Scale Sludge Anaerobic Digestion Plant.

Anaerobic digestion (AD) is an important biological resource recovery process, where microorganisms play key roles for material transformation. There has been some knowledge about the prokaryotic community and antibiotic resistance genes (ARGs) in AD, but there has been very limited knowledge of phages. In this study, samples from a full-scale AD plant were collected over 13 months, sequenced, and analyzed for viral and prokaryotic metagenomes. Totally, 3015 viral operational taxonomic units (vOTUs) were detected, mostly assigned to Caudoviricetes. The phage community had faster temporal variation than the prokaryotic community. Warm seasons harbored a higher abundance of both temperate phages and broad host-range phages. Seven ARGs of 6 subtypes were carried by 20 vOTUs, a representative ermT gene was synthesized and expressed, and the resistance activity in the host was examined, confirming the real activity of virus-carried ARGs in the AD process. Some of the ARGs were horizontally transferred between the phage and prokaryotic genomes. However, phage infection was not found to contribute to ARG transfer. This study provided an insight into the ecological patterns of the phage community, confirmed the antibiotic resistance activity of virus-carried ARGs, evaluated the contribution of phages on the ARG prevalence, and laid the foundation for the control strategies of the community and antibiotic resistance in the AD process.

Viruses of Nitrogen-Fixing Mesorhizobium Bacteria in Globally Distributed Chickpea Root Nodules

Legume nodules are specialized environments on plant roots that are induced and dominated by nitrogen-fixing bacteria. Bacteriophages (phages) in these nodules could potentially provide top-down controls on the population size and, therefore, the function of nitrogen-fixing symbionts. Here we sought to characterize the diversity and biogeographical patterns of phages that infect nitrogen-fixing Mesorhizobium symbionts isolated from root nodules, leveraging 266 genomes of Mesorhizobium isolated from nodules and 648 nodule metagenomes collected from three species of chickpea plants ( Cicer spp.) under different agricultural management practices, spanning eight countries on five continents. We identified 106 phage populations (viral operational taxonomic units [vOTUs]) in Mesorhizobium draft genomes, 37% of which were confirmed as likely prophages. These vOTUs were detected in 64% of the Mesorhizobium-dominated nodule metagenomes and 58% of the Mesorhizobium isolates. Per metagenome, 1 to 16 putative Mesorhizobium vOTUs were detected, with more than half of the nodules containing only one such vOTU. The majority of vOTUs were detected exclusively in Ethiopia, followed by India and Morocco, with the lowest richness of putative Mesorhizobium phages in countries that applied industrial Mesorhizobium inoculants to crops. Two vOTUs were identified in five or more countries and in nodules dominated by different strains of Mesorhizobium, suggesting infection of diverse Mesorhizobium hosts and long-term interactions. Beta-diversity of these Mesorhizobium phage assemblages was significantly correlated with the dominant Mesorhizobium strain, but not with measured environmental parameters. Our findings indicate that nitrogen-fixing nodules in chickpea plants can contain distinct viral assemblages, with potential impacts on the nodule microbiome that bear further exploration.

The multi-kingdom microbiome catalog of the chicken gastrointestinal tract

Chicken is an important food animal worldwide and plays an important role in human life by providing meat and eggs. Despite recent significant advances in gut microbiome studies, a comprehensive study of chicken gut bacterial, archaeal, and viral genomes remains unavailable. In this study, we constructed a chicken multi-kingdom microbiome catalog (CMKMC), including 18,201 bacterial, 225 archaeal, and 33,411 viral genomes, and annotated over 6,076,006 protein-coding genes by integrating 135 chicken gut metagenomes and publicly available metagenome-assembled genomes (MAGs) from ten countries. We found that 812 and 240 MAGs in our dataset were putative novel species and genera, respectively, far beyond what was previously reported. The newly unclassified MAGs were predominant in Phyla Firmicutes_A (n = 263), followed by Firmicutes (n = 126), Bacteroidota (n = 121), and Proteobacteria (n = 87). Most of the classified species-level viral operational taxonomic units belong to Caudovirales. Approximately, 63.24 % of chicken gut viromes are predicted to infect two or more hosts, including complete circular viruses. Moreover, we found that diverse auxiliary metabolic genes and antibiotic resistance genes were carried by viruses. Together, our CMKMC provides the largest integrated MAGs and viral genomes from the chicken gut to date, functional insights into the chicken gastrointestinal tract microbiota, and paves the way for microbial interventions for better chicken health and productivity.

Total metagenomes outperform viromes in recovering viral diversity from sulfuric soils.

Recent metagenomic advancements have offered unprecedented insights into soil viral ecology. However, it remains a challenge to select the suitable metagenomic method for investigating soil viruses under different environmental conditions. Here, we assessed the performance of viral size-fraction metagenomes (viromes) and total metagenomes in capturing viral diversity from hypersulfidic soils with neutral pH and sulfuric soils with pH <3.3. Viromes effectively enhanced the sequencing coverage of viral genomes in both soil types. Viomes of hypersulfidic soils outperformed total metagenomes by recovering a significantly higher number of viral operational taxonomic units (vOTUs). However, total metagenomes of sulfuric soils recovered ~4.5 times more vOTUs than viromes on average. Altogether, our findings suggest that the choice between viromes and total metagenomes for studying soil viruses should be carefully considered based on the specific environmental conditions.

Efficient Recovery of Complete Gut Viral Genomes by Combined Short- and Long-Read Sequencing.

Current metagenome assembled human gut phage catalogs contained mostly fragmented genomes. Here, comprehensive gut virome detection procedure is developed involving virus-like particle (VLP) enrichment from ≈500 g feces and combined sequencing of short- and long-read. Applied to 135 samples, a Chinese Gut Virome Catalog (CHGV) is assembled consisting of 21,499 non-redundant viral operational taxonomic units (vOTUs) that are significantly longer than those obtained by short-read sequencing and contained ≈35% (7675) complete genomes, which is ≈nine times more than those in the Gut Virome Database (GVD, ≈4%, 1,443). Interestingly, the majority (≈60%, 13,356) of the CHGV vOTUs are obtained by either long-read or hybrid assemblies, with little overlapwith those assembled from only the short-read data. With this dataset, vast diversity of the gut virome is elucidated, including the identification of 32%(6,962) novel vOTUs compare to public gut virome databases, dozens of phages that are more prevalent than the crAssphages and/or Gubaphages, and several viral clades that are more diverse than the two. Finally, the functional capacities are also characterized of the CHGV encoded proteins and constructed a viral-host interaction network to facilitate future research and applications.

High niche specificity and host genetic diversity of groundwater viruses.

Viruses are key members of microbial communities that exert control over host abundance and metabolism, thereby influencing ecosystem processes and biogeochemical cycles. Aquifers are known to host taxonomically diverse microbial life, yet little is known about viruses infecting groundwater microbial communities. Here, we analysed 16 metagenomes from a broad range of groundwater physicochemistries. We recovered 1571 viral genomes that clustered into 468 high-quality viral operational taxonomic units. At least 15% were observed to be transcriptionally active, although lysis was likely constrained by the resource-limited groundwater environment. Most were unclassified (95%), and the remaining 5% were Caudoviricetes. Comparisons with viruses inhabiting other aquifers revealed no shared species, indicating substantial unexplored viral diversity. In silico predictions linked 22.4% of the viruses to microbial host populations, including to ultra-small prokaryotes, such as Patescibacteria and Nanoarchaeota. Many predicted hosts were associated with the biogeochemical cycling of carbon, nitrogen, and sulfur. Metabolic predictions revealed the presence of 205 putative auxiliary metabolic genes, involved in diverse processes associated with the utilization of the host's intracellular resources for biosynthesis and transformation reactions, including those involved in nucleotide sugar, glycan, cofactor, and vitamin metabolism. Viruses, prokaryotes overall, and predicted prokaryotic hosts exhibited narrow spatial distributions, and relative abundance correlations with the same groundwater parameters (e.g. dissolved oxygen, nitrate, and iron), consistent with host control over viral distributions. Results provide insights into underexplored groundwater viruses, and indicate the large extent to which viruses may manipulate microbial communities and biogeochemistry in the terrestrial subsurface.

Uncovering differences in the composition and function of phage communities and phage-bacterium interactions in raw soy sauce.

Although the composition and succession of microbial communities in soy sauce fermentation have been well-characterized, the understanding of phage communities in soy sauce remains limited. This study determined the diversity, taxonomic composition, and predicted function of phage communities and the phage-host interactions in two types of raw soy sauce (Cantonese-type fermentation, NJ; Japanese-type fermentation, PJ) using shotgun metagenomics. These two raw soy sauces showed differences in phage composition (121 viral operational taxonomic units (vOTUs) in NJ and 387 vOTUs in PJ), with a higher abundance of the family Siphoviridae (58.50%) in the NJ phage community and a higher abundance of Myoviridae (33.01%) in PJ. Auxiliary metabolic functional annotation analyses showed that phages in the raw soy sauces mostly encoded genes with unknown functions (accounting for 66.33% of COG profiles), but the NJ sample contained genes mostly annotated to conventional functions related to carbohydrate metabolism (0.74%) and lipid metabolism (0.84%), while the PJ sample presented a higher level of amino acid metabolism functions (0.12%). Thirty auxiliary metabolism genes (AMGs) were identified in phage genomes, which were associated with carbohydrate utilization, cysteine and methionine metabolism, and aspartic acid biosynthesis for the host. To identify phage-host interactions, 30 host genomes (affiliated with 22 genera) were also recruited from the metagenomic dataset. The phage-host interaction analysis revealed a wide range of phage hosts, for which a total of 57 phage contigs were associated with 17 host genomes, with Shewanella fodinae and Weissella cibaria infected by the most phages. This study provides a comprehensive understanding of the phage community composition, auxiliary metabolic functions, and interactions with hosts in two different types of raw soy sauce.

Characterizations of the multi-kingdom gut microbiota in Chinese patients with gouty arthritis

ObjectiveThe gut microbial composition has been linked to metabolic and autoimmune diseases, including arthritis. However, there is a dearth of knowledge on the gut bacteriome, mycobiome, and virome in patients with gouty arthritis (GA).MethodsWe conducted a comprehensive analysis of the multi-kingdom gut microbiome of 26 GA patients and 28 healthy controls, using whole-metagenome shotgun sequencing of their stool samples.ResultsProfound alterations were observed in the gut bacteriome, mycobiome, and virome of GA patients. We identified 1,117 differentially abundant bacterial species, 23 fungal species, and 4,115 viral operational taxonomic units (vOTUs). GA-enriched bacteria included Escherichia coli_D GENOME144544, Bifidobacterium infantis GENOME095938, Blautia_A wexlerae GENOME096067, and Klebsiella pneumoniae GENOME147598, while control-enriched bacteria comprised Faecalibacterium prausnitzii_G GENOME147678, Agathobacter rectalis GENOME143712, and Bacteroides_A plebeius_A GENOME239725. GA-enriched fungi included opportunistic pathogens like Cryptococcus neoformans GCA_011057565, Candida parapsilosis GCA_000182765, and Malassezia spp., while control-enriched fungi featured several Hortaea werneckii subclades and Aspergillus fumigatus GCA_000002655. GA-enriched vOTUs mainly attributed to Siphoviridae, Myoviridae, Podoviridae, and Microviridae, whereas control-enriched vOTUs spanned 13 families, including Siphoviridae, Myoviridae, Podoviridae, Quimbyviridae, Phycodnaviridae, and crAss-like. A co-abundance network revealed intricate interactions among these multi-kingdom signatures, signifying their collective influence on the disease. Furthermore, these microbial signatures demonstrated the potential to effectively discriminate between patients and controls, highlighting their diagnostic utility.ConclusionsThis study yields crucial insights into the characteristics of the GA microbiota that may inform future mechanistic and therapeutic investigations.

Viral Diversity in Benthic Abyssal Ecosystems: Ecological and Methodological Considerations.

Viruses are the most abundant 'biological entities' in the world's oceans. However, technical and methodological constraints limit our understanding of their diversity, particularly in benthic abyssal ecosystems (>4000 m depth). To verify advantages and limitations of analyzing virome DNA subjected either to random amplification or unamplified, we applied shotgun sequencing-by-synthesis to two sample pairs obtained from benthic abyssal sites located in the North-eastern Atlantic Ocean at ca. 4700 m depth. One amplified DNA sample was also subjected to single-molecule long-read sequencing for comparative purposes. Overall, we identified 24,828 viral Operational Taxonomic Units (vOTUs), belonging to 22 viral families. Viral reads were more abundant in the amplified DNA samples (38.5-49.9%) compared to the unamplified ones (4.4-5.8%), with the latter showing a greater viral diversity and 11-16% of dsDNA viruses almost undetectable in the amplified samples. From a procedural point of view, the viromes obtained by direct sequencing (without amplification step) provided a broader overview of both ss and dsDNA viral diversity. Nevertheless, our results suggest that the contextual use of random amplification of the same sample and long-read technology can improve the assessment of viral assemblages by reducing off-target reads.

Global diversity and biogeography of DNA viral communities in activated sludge systems

BackgroundActivated sludge (AS) systems in wastewater treatment plants (WWTPs) harbor enormous viruses that regulate microbial metabolism and nutrient cycling, significantly influencing the stability of AS systems. However, our knowledge about the diversity of viral taxonomic groups and functional traits in global AS systems is still limited. To address this gap, we investigated the global diversity and biogeography of DNA viral communities in AS systems using 85,114 viral operational taxonomic units (vOTUs) recovered from 144 AS samples collected across 54 WWTPs from 13 different countries.ResultsAS viral communities and their functional traits exhibited distance-decay relationship (DDR) at the global scale and latitudinal diversity gradient (LDG) from equator to mid-latitude. Furthermore, it was observed that AS viral community and functional gene structures were largely driven by the geographic factors and wastewater types, of which the geographic factors were more important. Carrying and disseminating auxiliary metabolic genes (AMGs) associated with the degradation of polysaccharides, sulfate reduction, denitrification, and organic phosphoester hydrolysis, as well as the lysis of crucial functional microbes that govern biogeochemical cycles were two major ways by which viruses could regulate AS functions. It was worth noting that our study revealed a high abundance of antibiotic resistance genes (ARGs) in viral genomes, suggesting that viruses were key reservoirs of ARGs in AS systems.ConclusionsOur results demonstrated the highly diverse taxonomic groups and functional traits of viruses in AS systems. Viral lysis of host microbes and virus-mediated HGT can regulate the biogeochemical and nutrient cycles, thus affecting the performance of AS systems. These findings provide important insights into the viral diversity, function, and ecology in AS systems on a global scale.-K8pwvbs3fYC6bGWQ-q_MyVideo

Ecogenomics and cultivation reveal distinctive viral-bacterial communities in the surface microlayer of a Baltic Sea slick

Visible surface films, termed slicks, can extensively cover freshwater and marine ecosystems, with coastal regions being particularly susceptible to their presence. The sea-surface microlayer (SML), the upper 1-mm at the air-water interface in slicks (herein slick SML) harbors a distinctive bacterial community, but generally little is known about SML viruses. Using flow cytometry, metagenomics, and cultivation, we characterized viruses and bacteria in a brackish slick SML in comparison to non-slick SML as well as seawater below slick and non-slick areas (subsurface water = SSW). Size-fractionated filtration of all samples distinguished viral attachment to hosts and particles. The slick SML contained higher abundances of virus-like particles, prokaryotic cells, and dissolved organic carbon compared to non-slick SML and SSW. The community of 428 viral operational taxonomic units (vOTUs), 426 predicted as lytic, distinctly differed across all size fractions in the slick SML compared to non-slick SML and SSW. Specific metabolic profiles of bacterial metagenome-assembled genomes and isolates in the slick SML included a prevalence of genes encoding motility and carbohydrate-active enzymes (CAZymes). Several vOTUs were enriched in slick SML, and many virus variants were associated with particles. Nine vOTUs were only found in slick SML, six of them being targeted by slick SML-specific clustered-regularly interspaced short palindromic repeats (CRISPR) spacers likely originating from Gammaproteobacteria. Moreover, isolation of three previously unknown lytic phages for Alishewanella sp. and Pseudoalteromonas tunicata, abundant and actively replicating slick SML bacteria, suggests that viral activity in slicks contributes to biogeochemical cycling in coastal ecosystems.

Interrogating the viral dark matter of the rumen ecosystem with a global virome database

The diverse rumen virome can modulate the rumen microbiome, but it remains largely unexplored. Here, we mine 975 published rumen metagenomes for viral sequences, create a global rumen virome database (RVD), and analyze the rumen virome for diversity, virus-host linkages, and potential roles in affecting rumen functions. Containing 397,180 species-level viral operational taxonomic units (vOTUs), RVD substantially increases the detection rate of rumen viruses from metagenomes compared with IMG/VR V3. Most of the classified vOTUs belong to Caudovirales, differing from those found in the human gut. The rumen virome is predicted to infect the core rumen microbiome, including fiber degraders and methanogens, carries diverse auxiliary metabolic genes, and thus likely impacts the rumen ecosystem in both a top-down and a bottom-up manner. RVD and the findings provide useful resources and a baseline framework for future research to investigate how viruses may impact the rumen ecosystem and digestive physiology.

Genome mining shows that retroviruses are pervasively invading vertebrate genomes

Endogenous retroviruses (ERVs) record past retroviral infections, providing molecular archives for interrogating the evolution of retroviruses and retrovirus-host interaction. However, the vast majority of ERVs are not active anymore due to various disruptive mutations, and ongoing retroviral invasion of vertebrate genomes has been rarely documented. Here we analyze genomics data from 2004 vertebrates for mining invading ERVs (ERVi). We find that at least 412 ERVi elements representing 217 viral operational taxonomic units are invading the genomes of 123 vertebrates, 18 of which have been assessed to be threatened species. Our results reveal an unexpected prevalence of ongoing retroviral invasion in vertebrates and expand the diversity of retroviruses recently circulating in the wild. We characterize the pattern and nature of ERVi in the historical and biogeographical context of their hosts, for instance, the generation of model organisms, sympatric speciation, and domestication. We suspect that these ERVi are relevant to conservation of threatened species, zoonoses in the wild, and emerging infectious diseases in humans.

Viruses in deep-sea cold seep sediments harbor diverse survival mechanisms and remain genetically conserved within species

Deep sea cold seep sediments have been discovered to harbor novel, abundant, and diverse bacterial and archaeal viruses. However, little is known about viral genetic features and evolutionary patterns in these environments. Here, we examined the evolutionary ecology of viruses across active and extinct seep stages in the area of Haima cold seeps in the South China Sea. A total of 338 viral operational taxonomic units are identified and linked to 36 bacterial and archaeal phyla. The dynamics of host-virus interactions are informed by diverse antiviral defense systems across 43 families found in 487 microbial genomes. Cold seep viruses are predicted to harbor diverse adaptive strategies to persist in this environment, including counter-defense systems, auxiliary metabolic genes, reverse transcriptases, and alternative genetic code assignments. Extremely low nucleotide diversity is observed in cold seep viral populations, being influenced by factors including microbial host, sediment depth, and cold seep stage. Most cold seep viral genes are under strong purifying selection with trajectories that differ depending on whether cold seeps are active or extinct. This work sheds light on the understanding of environmental adaptation mechanisms and evolutionary patterns of viruses in the sub-seafloor biosphere.

Comparative analysis of gut DNA viromes in wild and captive Himalayan vultures.

Himalayan vultures (Gyps hinalayensis) are widely distributed on the Qinghai-Tibetan Plateau and play a crucial role in maintaining the ecological balance by feeding on decayed corpses of wild and domestic animals. Large-scale culture and metagenomics studies have broadened our understanding of viral diversity in animals' gastrointestinal tracts. However, despite the importance of gut viral communities in regulating bacterial diversity and performing symbiotic functions, no gut viral study has been conducted on Himalayan vultures. Furthermore, the impact of captivity on the gut virome of these vultures remains unknown. In this study, metagenomic sequencing methods targeting DNA of virus-like particles enriched from feces were used to characterize the gut DNA viromes of wild and captive Himalayan vultures. In total, 22,938 unique viral operational taxonomic units (vOTUs) were identified and assigned to 140 viral genera in 41 viral families. These families included viruses associated with bacteria, animals, plants, insects, and archaea. Phage communities, including Siphoviridae, Microviridae, Myoviridae, Inoviridae, and Herelleviridae, dominated the gut virome of Himalayan vultures. Wild vultures exhibited higher viral richness and diversity compared with those in captivity. The functional capacity of the gut virome was characterized by identifying 93 KEGG pathways, which were significantly enriched in metabolism and genetic information processing. Abundant auxiliary metabolic genes, such as carbohydrate-active enzyme, and antibiotic resistance genes, were also found in the vultures' gut virome. Our findings reveal the complex and diverse viral community present in the gut virome of Himalayan vultures, which varies between wild, and captive states. The DNA virome dataset establishes a baseline for the vultures' gut virome and will serve as a reference for future virus isolation and cultivation. Understanding the impact of captivity on the gut virome contributes to our knowledge of vultures' response to captivity and aids in optimizing their rehabilitation and implementing protective measures.

Virus–pathogen interactions improve water quality along the Middle Route of the South-to-North Water Diversion Canal

Bacterial pathogens and viruses are the leading causes of global waterborne diseases. Here, we discovered an interesting natural paradigm of water “self-purification” through virus–pathogen interactions over a 1432 km continuum along the Middle Route of the South-to-North Water Diversion Canal (MR-SNWDC) in China, the largest water transfer project in the world. Due to the extremely low total phosphorus (TP) content (ND-0.02 mg/L) in the MR-SNWDC, the whole canal has experienced long-lasting phosphorus (P) limitation since its operation in 2015. Based on 4443 metagenome-assembled genomes (MAGs) and 40,261 nonredundant viral operational taxonomic units (vOTUs) derived from our recent monitoring campaign, we found that residential viruses experiencing extreme P constraints had to adopt special adaptive strategies by harboring smaller genomes to minimize nucleotide replication, DNA repair, and posttranslational modification costs. With the decreasing P supply downstream, bacterial pathogens showed repressed environmental fitness and growth potential, and a weakened capacity to maintain P acquisition, membrane formation, and ribonucleotide biosynthesis. Consequently, the unique viral predation effects under P limitation, characterized by enhanced viral lytic infections and an increased abundance of ribonucleotide reductase (RNR) genes linked to viral nuclear DNA replication cycles, led to unexpectedly lower health risks from waterborne bacterial pathogens in the downstream water-receiving areas. These findings highlighted the great potential of water self-purification associated with virus–pathogen dynamics for water-quality improvement and sustainable water resource management.