Biology subjects

Rahlff, J.

Publications and source records attributed to Rahlff, J..

At least 19 recordsLinked to original sources

bioRxiv2026

First community challenge for automated virus taxonomy

The rapid rate of virus discovery renders manual curation by taxonomy experts increasingly impractical, creating a need for reliable software that can reproducibly assign viral contigs to taxa at all fifteen ranks of the virus taxonomy. We led an open community challenge for the computational taxonomic classification of viruses and assembled a dataset of virus sequences combining expert-curated and metagenomic sequences. Seventeen teams contributed a total of thirty-four automated, fully reproducible classification pipelines. Most tools correctly assigned viruses belonging to established species, genera, or families, but viruses that are unclassified at those lower ranks remain challenging. This study provides datasets, open-source software, novel approaches, and recommendations to benchmark computational taxonomic classification of viruses, and support organizing the many viruses discovered in big omics data.

microbiology↗

bioRxiv2026

Virus-host interactions on volcanic ash from Mount Etna

Volcanic ash represents an extreme and dynamic habitat, yet it hosts diverse microbial communities with largely unexplored viral diversity. This study investigated bacterial and viral populations in volcanic ash from Mount Etna (Italy) collected during the eruption, focusing on microbial novelty, activity, and virus-host interactions. Taxonomic profiling revealed that Pseudomonas and Telluria were the dominant bacterial genera, both frequently detected in airborne environments. In contrast, enrichment cultures with volcanic ash were dominated by spore-forming members of the phylum Bacillota, highlighting their resilience under harsh conditions. Metagenomic analysis recovered 19 high-quality metagenome-assembled genomes, including four previously undescribed bacterial species. Replication rate estimates showed that certain taxa were metabolically active, particularly at one sampling site. The presence of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) systems with spacers matching viral sequences suggested viral predation pressure on volcanic ash. A total of 1139 viral operational taxonomic units (vOTUs) were identified, of only around half (660 vOTUs) showed similarities to known phages, underscoring the presence of novel viruses. Shared vOTUs across sites revealed the presence of both a core virome and site-specific viral populations. Virus-host predictions indicated frequent interactions with hosts from multiple Gammaproteobacterial genera. Additionally, a 336 kb jumbo phage genome exhibited extensive metabolic capabilities and genetic autonomy. Experimental work identified a unique lytic Bacillus-infecting phage ("Phoenix") with limited propagation capacity. Furthermore, prophage induction experiments revealed active, morphologically diverse temperate phages across multiple bacterial host strains. Overall, these findings highlight volcanic ash as a reservoir of microbial and viral diversity, shaped by environmental extremes and dynamic ecological interactions. HighlightsMetagenomic and cultivation experiments were used to study viruses on volcanic ash Novelty of viral and bacterial species was detected Viral-bacterial interactions in metagenomes from volcanic ash were detected Cultivatable bacteria were mainly spore-forming Bacilli species and harbored inducible prophages

microbiology↗

bioRxiv2026

Virus-host interactions and viral population dynamics across atmospheric cloud events

BackgroundCloud water harbors diverse microbial communities despite its extreme oligotrophic conditions. However, the ecological and evolutionary dynamics of viruses in these transient atmospheric habitats remain poorly understood. Clouds have traditionally been regarded primarily as passive carriers of microorganisms rather than as active ecological environments supporting microbial interactions. In this study, cloud water was sampled at Mount Verde, Cape Verde Islands (744 m a.s.l.). We performed metagenomic analyses of iron-flocculated cloud water alongside genome analyses of a bacterial isolate and metagenome-assembled genomes using established bioinformatic approaches. Viral diversity, virus-host interactions, metabolic functions, genetic adaptations, and viral population dynamics across cloud events were investigated. In addition, UV-B resistance experiments were conducted for a novel cloud-water isolate. ResultsWe isolated 24 cloud water bacteria, including four novel species lineages, and recovered 62 high-quality metagenome-assembled genomes, including 10 novel species lineages. We identified 458 viral operational taxonomic units and 237 virus-host linkages across diverse prokaryotic hosts, revealing active viral predation across diverse bacterial taxa. In addition, CRISPR spacer matches from isolates of novel bacterial lineages such as Deinococcus nubigenus MPC36 were found. Viruses carried genes involved in host adaptation to environmental stressors, including cold-shock response, UV radiation resistance, and osmotic stress. In addition, viral populations exhibited SNP-level microdiversity and shifts in single-nucleotide variant composition across temporally proximate cloud events, indicating rapid population turnover. Experimental characterization of the cloud isolate Curtobacterium nubigenum MPC39 further revealed pronounced resistance to UV-B radiation and the presence of an inducible prophage, Curtobacterium phage vB_CnuS_Cirrus1 assigned to the new viral family Nebulaviridae, which could be validated in transmission electron microscopy. Reconstructed genomes from cloud-associated bacteria encoded carbon monoxide dehydrogenase genes and UV resistance genes, suggesting trace gas metabolism and enhanced UV protection as survival strategies in oligotrophic cloud droplets. In silico replication rates estimated using iRep were consistent with active bacterial replication at the time of sampling. ConclusionsTogether, these findings demonstrate that clouds are not merely passive carriers of microorganisms, but dynamic atmospheric ecosystems in which virus-host interactions shape microbial diversity and contribute to microbial turnover, atmospheric dispersal, and cloud-water biogeochemistry.

microbiology↗

bioRxiv2026

Viral communities in Metania sp. sponge microbiomes with possible effects on CO2 fixation

BackgroundBrazilian sponges of the genus Metania (phylum Porifera) are filter-feeding organisms from freshwater ecosystems. Here, we explored viral communities of Metania sp., their functional role in the sponge and how they differ from those in surrounding water. ResultsWe identified 1163 viral operational taxonomic units (vOTUs) from sponge tissue and adjacent water, with 555 vOTUs shared across habitats. Viral diversity was higher in sponges than in water, and community composition differed significantly (PERMANOVA, p = 0.037). Sponge-associated vOTUs exhibited broad phylogenetic diversity, including deep-branching and unclassified clades, and several exclusively sponge-associated Caudoviricetes. Virus-host predictions revealed 173 interactions, largely with sponge-associated bacteria, supported by CRISPR spacer matches, variant formation in multiple vOTUs across sponge individuals, and a high prevalence of microbial defence systems, particularly restriction-modification, abortive infection, and CRISPR-Cas pathways. Functionally, viral communities carried diverse auxiliary viral genes, including those involved in amino acid and central carbon metabolism, carbohydrate degradation, fatty acid biosynthesis, stress responses (e.g., metacaspase-1), and sulphur cycling. Nine sponge-associated vOTUs encoded carbonic anhydrase (CA), and phylogenomic as well as structural analyses showed strong conservation of CA active sites between sponge viruses, bacterial symbionts, and the sponge host. Protein-level homology searches revealed broad biogeographic distribution of viral CA homologs across global ocean microbiomes, despite limited nucleotide similarity, highlighting deep functional conservation. ConclusionsThese findings reveal a phylogenetically diverse and functionally rich viral community associated with freshwater Metania sp., characterized by extensive host interactions, diverse defence mechanisms, and auxiliary metabolic capacities. The structural conservation and widespread distribution of viral carbonic anhydrase genes further suggest ecologically significant roles in carbon transformation within freshwater sponges and potentially across aquatic ecosystems.

microbiology↗

bioRxiv2025

Biogeochemical function of slicks in coastal surface waters of the Baltic Sea

The sea-surface microlayer (SML) is a crucial ocean-atmosphere interface involved in gas exchange and nutrient cycling. Slicks, i.e., viscous surface layers, common in coastal regions serve as microbial hotspots. We studied microbial abundance, surfactants, dissolved organic carbon (DOC), and net community production (NCP) of O2 in slick and non-slick SMLs and underlying water (ULW) in the coastal Baltic Sea. Slicks often showed higher surfactant levels compared to the ULW. Microbial respiration often exceeded production, resulting in net O2 consumption, although some ULW sites exhibited net O2 production. The SML was enriched with pico- and nanophytoplankton, with cyanobacteria being negatively correlated with total dissolved nitrogen. In contrast, microphytoplankton accumulated in the ULW, indicating niche separation with depth. Microscopy revealed ciliates and juvenile sporophytes dominating a slicks >100 {micro}m fraction. In eutrophic coastal systems, slicks influence plankton communities and O2 dynamics, supporting their role in surface biogeochemical cycling and climate-driven changes.

microbiology↗

bioRxiv2024

Spatio-temporal variability of airborne viruses over sub-Antarctic South Georgia: Effects of sampling device and proximity of the ocean

Studying airborne viruses in remote environments like the sub-Antarctic island South Georgia offers key insights into viral ecology, diversity, and their role in shaping ecosystems through microbial and nutrient interactions. We analyzed airborne viral community composition at two sites in South Georgia. Sampling took place using multiple methodologies, with the data produced subjected to viral metagenomics. The Coriolis {micro} device (wet collection) was the most effective, yielding 30 viral scaffolds. Two-thirds of the scaffolds were only obtained from the coastal location, indicating that location influences airborne viral diversity. Protein-based clustering of 39 viral operational taxonomic units (vOTUs) revealed similarities of 15 with known marine viruses, suggesting oceanic influence on the airborne viral community. Protein homologs related to UV damage protection and photosynthesis from two airborne vOTUs were widely distributed across major oceans, suggesting their potential role in supporting the resilience of marine microorganisms under changing climate conditions. Some vOTUs had protein similarities to viruses infecting extremophiles, indicating viral adaptations to harsh environments. This study provides a baseline for understanding the complexity and sustainability of airborne viral communities in remote ecosystems. It underscores the need for continued monitoring to assess how these communities respond to shifting atmospheric and ecological conditions.

microbiology↗

bioRxiv2024

Phage genome architecture and GC content: Structural genes and where to find them

Bacteriophages, the ubiquitous bacterial viruses, are the most abundant biological entities on Earth. However, information regarding the impact of environmental factors on the genetic makeup of phages is scarce. Based on the analysis of genomes of 45 phage isolates from different ecosystems we demonstrate a significant (p < 0.0001) positive correlation of the number of structural genes and their placement in above-average guanine-cytosine (GC) content of the genome. This feature appears to be more evident in isolates from deep-sea and sea-ice environments compared to desert and Baltic Sea slick, indicating a potential ecosystem-based factor (although insignificant due to low sample size). Additionally, the percentage of structural genes in above-average GC regions was found to be significantly (p = 0.0038) negatively correlated with the genome size of the phages and significantly (p = 0.0266) positively correlated with the overall GC for phage genomes > 50 kb, but not for genomes < 50 kb (p = 0.556). We therefore propose a relationship of structural genes and GC content, a property that may influence the adaptation and evolution of phages in various environmental niches.

microbiology↗

bioRxiv2024

Viral challenges and adaptations between Central Arctic Ocean and atmosphere

Aquatic viruses act as key players in shaping microbial communities. In polar environments, they face significant challenges like limited host availability and harsh conditions. However, due to restricted ecosystem accessibility, our understanding of viral diversity, abundance, adaptations, and host interactions remains limited. To fill this knowledge gap, we studied viruses from atmosphere-close aquatic ecosystems in the Central Arctic and Northern Greenland. Aquatic samples for virus-host analysis were collected from ~60 cm depth and the submillimeter surface microlayer (SML) during the Synoptic Arctic Survey 2021 on icebreaker Oden in Arctic summer. Water was sampled from a melt pond and open water before undergoing size-fractioned filtration and followed by genome-resolved metagenomic and cultivation investigations. The prokaryotic diversity in the melt pond was considerably lower compared to open water. The melt pond was dominated by a Flavobacterium sp. and Aquiluna sp., the latter having a relatively small genome size of 1.2 Mb and the metabolic potential to generate ATP using the phosphate acetyltransferase-acetate kinase pathway. Viral diversity on the host fraction (0.2 - 5 {micro}m) of the melt pond was strikingly limited compared to open water. From 1154 dereplicated viral operational taxonomic units (vOTUs), of which two-thirds were predicted bacteriophages, 17.2% encoded for auxiliary metabolic genes (AMGs) with metabolic functions. Some AMGs like glycerol-3-phosphate cytidylyltransferase and ice-binding like proteins might serve cryoprotection of the host. Prophages were often associated with SML genomes, and two active prophages of a new viral genera from the Arctic SML strain Leeuwenhoekiella aequorea Arc30 were induced. We found evidence that vOTU abundance in the SML compared to ~60 cm depth was more positively correlated to the distribution of a vOTU across five different Arctic stations. The results indicate that viruses employ elaborated strategies to endure in extreme and host-limited environments. Moreover, our observations suggest that the immediate air-sea interface serves as a platform for viral distribution in the Central Arctic.

microbiology↗

bioRxiv2023

Ecogenomics reveals distinctive viral-bacterial communities in the surface microlayer of a natural surface slick

Visible surface films, termed slicks, can extensively cover the sea surface, particularly in coastal regions. The sea-surface microlayer (SML), the upper 1-mm at the air-water interface in slicks (slick SML) harbors a distinctive bacterial community, but little is known about SML viruses. Using flow cytometry, metagenomics, and cultivation, we investigated viruses and the bacterial community from a brackish slick SML in comparison to non-slick SML as well as the seawater below (SSW). We conducted size-fractionated filtration of all samples to distinguish 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. The distinctness was underlined by specific metabolic profiles of bacterial metagenome assembled genomes and isolates, which revealed prevalence of motility genes and diversity of CAZymes in the slick SML. Despite overall lower diversity, several vOTUs were enriched in slick SML over slick SSW. Nine vOTUs were only found in slick SML and six of them were targeted by slick SML-specific CRISPR spacers likely originating from Gammaproteobacteria. Moreover, isolation of three previously unknown lytic phages for Alishewanella sp. and Pseudoalteromonas tunicata, representing abundant and actively replicating slick SML bacteria, suggests that viral activity in slicks can contribute to biogeochemical cycling in coastal ecosystems.

microbiology↗

bioRxiv2023

Virus-host dynamics in archaeal groundwater biofilms and the associated bacterial community composition

Lytic viruses can be prevalent in deep groundwater, yet their spatial and temporal distribution in such an ecosystem remains unexplored. Here, we tackle this gap of knowledge by studying viral infections in individual, archaea-dominated biofilm flocks sampled from deep anoxic groundwater over a period of three years. Using virusFISH whose detection efficiency for individual viral particles was 15%, we show a significant and steady increase of virus infections between the years 2019 and 2022. Based on various fluorescence micrographs of individual biofilm flocks, we determined different stages of viral infections in biofilms for single sampling events, demonstrating the progression of infection of biofilms in deep groundwater. Biofilms associated with many host cells undergoing lysis showed a substantial accumulation of filamentous microbes around infected cells probably feeding off host cell debris. Using 16S rRNA gene sequencing across ten individual biofilm flocks from one sampling event, we determined that the associated bacterial community remains relatively constant and was dominated by Desulfobacterota. Given the stability of the virus-host interaction in these deep groundwater samples, we postulate that the virus-host dynamics of Ca. Altiarchaeum hamiconexum and its abundant virus Altivir_l_MSI described herein represent a suitable model system for studying deep biosphere virus-host interactions in future research endeavors.

microbiology↗

bioRxiv2023

Co-evolutionary patterns shown in Ostreococcus-virus system from the Western Baltic Sea in freshly isolated hosts and viruses.

Marine viruses are a major driver of phytoplankton mortality and thereby influence biogeochemical cycling of carbon and other nutrients. In recent years, an understanding of the potential importance of phytoplankton-targeting viruses on ecosystem dynamics has emerged, but experimental investigations of host-virus interactions on a broad spatial and temporal scale are still missing. Here, we investigated in detail a phytoplankton hosts responses reacting to infections by species-specific viruses from i) distinct geographical regions and ii) different sampling seasons. Specifically, we used two species of picophytoplankton (1 {micro}m) Ostreococcus tauri and O. mediterraneus and their viruses (size ca. 100 nm), which represent systems well-known in marine biology, but almost entirely ignored in evolutionary biology. The strains stem from different regions of the Southwestern Baltic Sea that vary in salinity and temperature. Using an experimental cross-infection set-up, we show that in this natural system evolutionary history, and thus the timing of when hosts and their associated viruses coexisted, was the main driver of infection patterns. In addition species and strain specificity underline the present understanding of rapid host-virus co-evolution.

microbiology↗

bioRxiv2022

Heads in the clouds: marine viruses disperse bidirectionally along the natural water cycle

Marine viruses have thoroughly been studied in seawater, yet their dispersal from neuston ecosystems at the air-sea interface towards the atmosphere remains a knowledge gap. Here, we show that 6.2 % of the studied virus population were shared between air-sea interface ecosystems and rainwater. Virus enrichment in the 1-mm thin surface microlayer and sea foams happened selectively, and variant analysis proved virus transfer to aerosols and rain. Viruses detected in rain and aerosols showed a significantly higher percent G/C base content compared to marine viruses, and a genetically distinct rain virome supports that those viruses could inhabit higher air masses. CRISPR spacer matches of marine prokaryotes to "foreign" viruses from rainwater prove regular virus-host encounters at the air-sea interface. Our findings on aerosolization and long-range atmospheric dispersal implicate virus-mediated carbon turnover in remote areas, viral dispersal mechanisms relevant to human health, and involvement of viruses in atmospheric processes like ice-nucleation.

microbiology↗

bioRxiv2021

Host-associated phages disperse across the extraterrestrial analogue Antarctica

Extreme Antarctic conditions provide one of the closest analogues of extraterrestrial environments. Since air and snow samples, especially from polar regions, yield DNA amounts in the lower picogram range, binning of prokaryotic genomes is challenging and renders studying the dispersal of biological entities across these environments difficult. Here, we hypothesized that dispersal of host-associated bacteriophages (adsorbed, replicating or prophages) across the Antarctic continent can be tracked via their genetic signatures aiding our understanding of virus and host dispersal across long distances. Phage genome fragments (PGFs) reconstructed from surface snow metagenomes of three Antarctic stations were assigned to four host genomes, mainly Betaproteobacteria including Ralstonia spp. We reconstructed the complete genome of a temperate phage with near-complete alignment to a prophage in the reference genome of Ralstonia pickettii 12D. PGFs from different stations were related to each other at the genus level and matched similar hosts. Metagenomic read mapping and nucleotide polymorphism analysis revealed a wide dispersal of highly identical PGFs, 13 of which were detected in seawater from the Western Antarctic Peninsula in distance of 5538 km to the snow sampling stations. Our results suggest that host-associated phages, especially of Ralstonia sp., disperse over long distances despite harsh conditions of the Antarctic continent. Given that 14 phages associated with two R. pickettii draft genomes isolated from space equipment were identified, we conclude that Ralstonia phages are ideal mobile genetic elements to track dispersal and contamination in ecosystems relevant for Astrobiology. ImportanceHost-associated phages of the bacterium Ralstonia identified in snow samples can be used to track microbial dispersal over thousands of kilometers across the Antarctic continent, which functions as an extraterrestrial analogue because of its harsh environmental conditions. Due to presence of these bacteria carrying genome-integrated prophages on space-related equipment, and the here demonstrated potential for dispersal of host-associated phages, our work has implications for Planetary Protection, a discipline in Astrobiology interested in preventing contamination of celestial bodies with alien biomolecules or forms of life.

microbiology↗

bioRxiv2021

Virus-associated organosulfur metabolism in human and environmental systems

Viruses influence the fate of nutrients and human health by killing microorganisms and altering metabolic processes. Organosulfur metabolism and biologically-derived hydrogen sulfide play dynamic roles in manifestation of diseases, infrastructure degradation, and essential biological processes. While microbial organosulfur metabolism is well-studied, the role of viruses in organosulfur metabolism is unknown. Here we report the discovery of 39 gene families involved in organosulfur metabolism encoded by 3,749 viruses from diverse ecosystems, including human microbiomes. The viruses infect organisms from all three domains of life. Six gene families encode for enzymes that degrade organosulfur compounds into sulfide, while others manipulate organosulfur compounds and may influence sulfide production. We show that viral metabolic genes encode key enzymatic domains, are translated into protein, are maintained after recombination, and that sulfide provides a fitness advantage to viruses. Our results reveal viruses as drivers of organosulfur metabolism with important implications for human and environmental health.

microbiology↗

bioRxiv2020

Viruses carrying genes for microbial extremotolerance are abundant and widely dispersed in the Atacama Desert hyperarid soil

Viruses play an essential role in shaping microbial community structures and serve as reservoirs for genetic diversity in many ecosystems. In hyperarid desert environments, where life itself becomes scarce and loses diversity, the interactions between viruses and host populations have remained elusive. Here, we resolved host-virus interactions in the soil metagenomes of the Atacama Desert hyperarid core, one of the harshest terrestrial environments on Earth. We show evidence of diverse viruses infecting a wide range of hosts found in sites up to 205 km apart. Viral genomes carried putative extremotolerance features (i.e. DNA repair proteins, enzymes against oxidative damage, spore formation proteins) and auxiliary metabolic genes, indicating that viruses could mediate the spread of microbial resilience against environmental stress across the desert. We propose a mutualistic model of host-virus interactions in the hyperarid core where viruses seek protection in microbial cells as lysogens or pseudolysogens, while viral extremotolerance genes aid survival of their hosts. Our results suggest that the host-virus interactions in the Atacama Desert soils are dynamic and complex, shaping uniquely adapted microbiomes in this highly selective and hostile environment. ImportanceDeserts are one of the largest and rapidly expanding terrestrial ecosystems characterized by low biodiversity and biomass. The hyperarid core of the Atacama Desert, previously thought to be devoid of life, is one of the harshest environments supporting only scant biomass of highly adapted microbes. While there is growing evidence that viruses play essential roles in shaping the diversity and structure of nearly every ecosystem, very little is known about the role of viruses in desert soils, especially where viral contact with viable hosts is significantly reduced. Our results indicate that diverse viruses are widely dispersed across the desert, potentially spreading key stress resilience and metabolic genes to ensure host survival. The desertification accelerated by climate change expands both the ecosystem cover and the ecological significance of the desert virome. This study sheds light on the complex virus-host interplay that shapes the unique microbiome in desert soils.

microbiology↗

bioRxiv2020

Genome-informed microscopy reveals infections of uncultivated carbon-fixing archaea by lytic viruses in Earth's crust

The continental subsurface houses a major portion of lifes abundance and diversity, yet little is known about viruses infecting microbes that reside there. Here, we used a combination of metagenomics and genome-informed microscopy to show that highly abundant carbon-fixing organisms of the uncultivated genus Candidatus Altiarchaeum are frequent targets of previously unrecognized viruses in the deep subsurface. Analysis of CRISPR spacer matches displayed resistances of Ca. Altiarchaea against eight predicted viral clades, which showed genomic relatedness across continents but little similarity to previously identified viruses. Based on metagenomic information, we tagged and imaged a putatively viral genome rich in protospacers using fluorescence microscopy. Virus-targeted genomeFISH revealed a lytic lifestyle of the respective virus and challenges previous predictions that lysogeny prevails as the dominant viral lifestyle in the subsurface. CRISPR development over time and imaging of 18 samples from one subsurface ecosystem suggest a sophisticated interplay of viral diversification and adapting CRISPR-mediated resistances of Ca. Altiarchaeum. We conclude that infections of primary producers with lytic viruses followed by cell lysis potentially jump-start heterotrophic carbon cycling in these subsurface ecosystems.

microbiology↗

bioRxiv2020

Short-term responses to ocean acidification: effects on relative abundance of eukaryotic plankton from the tropical Timor Sea

Anthropogenic carbon dioxide (CO2) emissions drive climate change and pose one of the major challenges of our century. The effects of increased CO2 in the form of ocean acidification (OA) on the communities of marine planktonic eukaryotes in tropical regions such as the Timor Sea are barely understood. Here, we show the effects of high CO2 (pCO2=1823{+/-}161 atm, pHT=7.46{+/-}0.05) versus in situ CO2 (pCO2=504{+/-}42 atm, pHT=7.95{+/-}0.04) seawater on the community composition of marine planktonic eukaryotes immediately and after 48 hours of treatment exposure in a shipboard microcosm experiment. Illumina sequencing of the V9 hypervariable region of 18S rRNA (gene) was used to study the eukaryotic community composition. Down-regulation of extracellular carbonic anhydrase occurred faster in the high CO2 treatment. Increased CO2 significantly suppressed the relative abundances of different eukaryotic operational taxonomic units (OTUs), including important primary producers. These effects were consistent between abundant (DNA-based) and active (cDNA-based) taxa after 48 hours, e.g., for the diatoms Trieres chinensis and Stephanopyxis turris. Effects were also very species-specific among different diatoms. Planktonic eukaryotes showed adaptation to the CO2 treatment over time, but many OTUs were adversely affected by decreasing pH. OA effects might fundamentally impact the base of marine biodiversity, suggesting profound outcomes for food web functioning in the future ocean.

ecology↗

bioRxiv2020

Geological degassing enhances microbial metabolism in the continental subsurface

Mantle degassing provides a substantial amount of reduced and oxidized gases shaping microbial metabolism at volcanic sites across the globe, yet little is known about its impact on microbial life under non-thermal conditions. Here, we characterized deep subsurface fluids from a cold-water geyser driven by mantle degassing using genome-resolved metagenomics to investigate how the gases impact the metabolism and activity of indigenous microbes compared to non-impacted sites. While species-specific analyses of Altiarchaeota suggest site-specific adaptations and a particular biogeographic pattern, chemolithoautotrophic core features of the communities appeared to be conserved across 17 groundwater ecosystems between 5 and 3200 m depth. We identified a significant negative correlation between ecosystem depth and bacterial replication, except for samples impacted by high amounts of subsurface gases, which exhibited near-surface activity. Our results suggest that geological degassing leads to higher nutrient flows and microbial activity in the deep subsurface than previously estimated.

microbiology↗