Biology subjects

Bornemann, T. L. V.

Publications and source records attributed to Bornemann, T. L. V..

15 recordsLinked to original sources

bioRxiv2026

Automated refinement of metagenomic bins and estimation of binning success using itBins

Most prokaryotic genomes in public databases are genomes reconstructed from metagenomes, forming a compendium of multiple contiguous sequences (contigs) assembled from shotgun sequencing data. Binning algorithms for assigning contigs to metagenome assembled genomes (MAGs) are manifold and continuously improving in accuracy. However, binning errors, i.e. the incorrect assignment of a contig and coding sequence to a MAG, often propagate through various databases and confound taxonomic, metabolic and/or evolutionary analyses. Here we present itBins, a fully automated python-based software that enables ultra-fast refinement of metagenomic bins using a rule-based approach harnessing information from %GC content (%GC for brevity), coverage, and taxonomy of individual contigs. When applied to the low, medium, and high complexity data of the Critical Assessment of Metagenome Interpretation (CAMI I) challenge [1], itBins produced higher F1 scores (the harmonic mean of precision and recall) for all levels compared to other automated refinement tools, i.e., MDMcleaner and Rosella. Compared to manual refinement via uBin, itBins performed similarly well across all three complexity levels of the CAMI I dataset. With an average speed of 61 ms per bin, itBins is faster than all other refinement tools by at least three orders of magnitude when input data is accordingly available (%GC, coverage, and taxonomy), and was similarly fast when input data preparation was included in the processing time. Application to 64 real-world metagenomes from highly complex river mesocosms resulted in 259 medium-quality and 19 high-quality MAGs refined by itBins, while the other automated refinement tools failed in generating output at all or within 5000 hours of runtime. Finally, itBins also utilizes marker genes to determine the overall binning success for individual metagenomes, providing a crucial benchmark for the user to estimate the ecological relevance of their binned data. The herein introduced software itBins is broadly applicable to any type of metagenome data, integrates well with other software like DASTool, and enables swift and reliable refinement of genomes from metagenomes along with estimation of the overall binning success. itBins is distributed via EUPL 1.2 license and available at Codeberg (codeberg.org/JMK/itBins), GitHub (github.com/ProbstLab/itBins) and through Bioconda [2](bioconda.github.io/recipes/itbins/README.html).

bioinformatics↗

bioRxiv2026

Novel Extended Tetraether Lipids Found in a High-CO2 Geyser

The growing research into the archaeal lipidome has uncovered a remarkable structural diversity in glycerol dialkyl glycerol tetraethers (GDGTs) and revealed complex membrane adaptations, especially in extreme environments. We performed a comprehensive analysis of the lipidome from the subsurface water of a CO2-rich, cold-water Geyser Andernach (Germany), using ultra-high-resolution mass spectrometry methods. We detected GDGT-0, presumably derived from the dominant community member Candidatus Altiarchaeum, providing evidence for its ability to synthesize tetraethers as previously predicted from metagenomic data. Beyond the typical GDGT-0 and acyclic glycerol trialkyl glycerol tetraether (GTGT-0), we discovered novel structural analogues, here referred to as extended GDGTs and GTGTs, characterized by the asymmetrical addition of up to two isoprenoid units to only one of their hydrocarbon side chains, analogous to those found in extended archaeols. The lack of GDGT ring synthase A (GrsA) and GrsB homologs in the corresponding metagenome-assembled genome, suggests that the producing archaeon may utilize extended GDGTs as a membrane adaptation to cope with the energy-depleted conditions of the geyser environment, highlighting the adaptive flexibility of archaea to extreme physicochemical conditions.

biochemistry↗

bioRxiv2025

Uranium mining fuels evolution in deep groundwater microbiomes

Deep-biosphere microbes have been underpinning global biogeochemical cycles throughout Earth history, yet their evolutionary responses to long-term anthropogenic disturbance remain poorly understood. Neutral-pH in-situ leaching (ISL), the dominant uranium-mining strategy, imposes persistent radiochemical and redox stress offering rare natural experiments across decades for observing subsurface microbial evolution. Here, by exploiting metagenomics and metatranscriptomics in examining microbial responses through various mining stages, we show that neutral U ISL causes substantial changes in microbial communities spanning 2,294 strains accompanied by diversification and selection of active microbial species. These changes occurred during elevated dissolved uranium and radiological activity which correlated with a substantial transcriptional change in energy metabolism, and with an overexpression of specific genes for oxidative-stress defence and DNA-repair pathways. Increased nucleotide diversity in 101 out of 392 species clusters and nonsynonymous/synonymous polymorphism ratios greater than one in 139 species clusters were predominantly observed in metatranscriptomes with elevated radiation, highlighting positive selection of transcriptionally active populations. These findings demonstrate that neutral U ISL drives functional and genetic diversification of subsurface microbiomes, revealing a dynamic and evolutionarily responsive deep biosphere.

genomics↗

bioRxiv2025

A uniform stress response of stream microbiomes in the hyporheic zone across North America

BackgroundStream hyporheic zones represent a unique ecosystem at the interface of stream water and surrounding sediments, characterized by high heterogeneity and accelerated biogeochemical activity. These zones are increasingly impacted by anthropogenic stressors and environmental changes at a global scale, directly altering their microbiomes. Despite their importance, the current body of literature lacks a systematic understanding of active nitrogen and sulfur cycling across stream sediment and surface water microbiomes, particularly across geographic locations and in response to environmental stressors. ResultsBased on previously published and unpublished datasets, 363 stream metagenomes were combined to build a comprehensive MAG and gene database from stream sediments and surface water including a full-factorial mesocosm experiment which had been deployed to unravel microbial stress response. Metatranscriptomic data from 23 hyporheic sediment samples collected across North America revealed that microbial activity in sediments was distinct from the activity in surface water, contrasting similarly encoded metabolic potential across the two compartments. The expressed energy metabolism of the hyporheic zone was characterized by increased cycling of sulfur and nitrogen compounds, governed by Nitrospirota and Desulfobacterota lineages. While core metabolic functions like energy conservation were conserved across sediments, temperature and stream order change resulted in differential expression of stress response genes previously observed in mesocosm studies. ConclusionsThe hyporheic zone is a microbial hotspot in stream ecosystems, surpassing the activity of overlaying riverine surface waters. Metabolic activity in the form of sulfur and nitrogen cycling in hyporheic sediments is governed by multiple taxa interacting through metabolic handoffs. Despite the spatial heterogeneity of streams, the hyporheic sediment microbiome encodes and expresses conserved stress responses to anthropogenic stressors, e.g., temperature, in streams of separate continents. The high number of uncharacterized differentially expressed genes as a response to tested stressors is a call-to-action to deepen the study of stream systems.

microbiology↗

bioRxiv2024

Inferring replication states of bacteria and viruses in enrichment cultures via long-read sequencing

Most microorganisms cannot be cultured in isolation, necessitating sophisticated methods for studying their (eco)physiology. While numerous approaches can probe the activity of given microbes in enrichment cultures, no single technique can render simultaneous data on both metabolic capacities and mobile genetic elements. Here, we apply long-read sequencing to monitor the incorporation of non-canonical bases in genome-resolved metagenomic datasets and elucidate the replication patterns of both bacteria and phages. This technology enables the simultaneous reconstruction of both prokaryotic and viral genomes (alongside genomics downstream analyses like metabolic predictions), in addition to providing information regarding their replication in enrichment cultures. By spiking the base analog 5-bromo-2-deoxyuridine (BrdU) into activated sludge microcosms, we determined that 114 of the 118 high-quality genomes recovered were actively replicating in enrichment cultures from activated sludge and identified both slow (low BrdU incorporation and change in abundance) and rapidly replicating organisms (high BrdU incorporation and change in abundance). Some of the genomes detected exhibited regions rich in BrdU that were predicted to represent prophages in their lytic cycle. Ultimately, this novel means of monitoring the replication responses of microbes, and deciphering their genomes and active mobile genetic elements will advance and empower strategies aimed at isolating previously uncultivated microbes in pure culture.

microbiology↗

bioRxiv2024

Complex compositional and cellular response of river sediment microbiomes to multiple anthropogenic stressors

Rivers face constant anthropogenic stressors, resulting in significant changes in microbial community composition. What remains unclear is whether these changes render the microbiome better adapted to the stressed environment. Here, by subjecting 64 river-connected mesocosms to multiple stressors, we show that sediment microbiomes of small lowland rivers are highly sensitive to lowered flow velocity resulting in substantially altered community compositions not fully capable of compensating for the stressor effect within two weeks albeit having stable functions encoded in metagenomes. Transcriptomics revealed a systematic heat shock response in the community and a highly active, previously unknown anaerobic key stone species with great metabolic versatility. Increases in temperature (+3.5 {degrees}C) or salinity (+0.5 mS/cm) were outcompeted by lowered flow and elicited only minor responses at community or transcriptomic level with, e.g., upregulation of the photosystem of chloroplasts. Following a two-week recovery period, transcriptomic stress responses vanished completely compared to control mesocosms, exemplifying the river microbiomes resilience. We conclude that, given the complex community responses at both the cellular and compositional level, maintaining natural river flow is vital to preventing energy loss and reduced microbiome activity in river sediments.

ecology↗

bioRxiv2023

Metaproteogenomics resolution of a high-CO2 aquifer community suggests an active symbiotic lifestyle of groundwater Gracilibacteria

BackgroundBacteria of the Candidate Phyla Radiation (CPR), constituting about 25% of the bacterial biodiversity, are characterized by small cell size and patchy genomes without complete key metabolic pathways, suggesting a symbiotic lifestyle. Gracilibacteria (BD1-5), which are part of the CPR branch, possess alternate coded genomes and have not yet been cultivated. However, besides genomic evidence, little is known about the lifestyle of Gracilibacteria, their temporal dynamics, and activity in natural ecosystems, particularly in groundwater, where they were initially been genomically resolved. Therefore, we here aimed to investigate Gracilibacteria activity in situ and to discern expressed genes involved in their lifestyle, using the metaproteogenome of Gracilibacteria as a function of time in the cold-water geyser Wallender Born in the Volcanic Eifel region in Germany. ResultsWe coupled genome-resolved metagenomics and metaproteomics to investigate a cold-water geyser microbial community enriched in Gracilibacteria across a 12-day time-series. Groundwater was collected and sequentially filtered to fraction CPR and other bacteria. Based on 670 Gbps of metagenomic data, 1129 different ribosomal protein S3 marker genes and 751 high-quality genomes (123 population genomes after dereplication), we identified dominant bacteria belonging to Galionellales and Gracilibacteria along with keystone microbes, which were low in genomic abundance but substantially contributing to proteomic abundance. Seven high-quality Gracilibacteria genomes showed typical limitations, such as limited amino acid or nucleotide synthesis, in their central metabolism but no co-occurrence with potential hosts. The genomes of these Gracilibacteria encoded for a high number of proteins related to a symbiotic or even predatory lifestyle, e.g., type IV and type II secretion system subunits and features related to cell-cell interactions and cell motility, which were also detected on protein level. ConclusionsCoupling metagenomics to metaproteomics enabled us to identify microbial keystone taxa in a high-CO2 aquifer, and to reveal microbial dynamics of Gracilibacteria. We posit that Gracilibacteria might be successful microbial predators in this ecosystem, potentially aiding in population control of this highly perturbed microbial geyser community from the deep biosphere.

ecology↗

bioRxiv2023

Dancing the Nanopore limbo - Nanopore metagenomics from small DNA quantities for bacterial genome reconstruction

BackgroundWhile genome-resolved metagenomics has revolutionized our understanding of microbial and genetic diversity in environmental samples, assemblies of short-reads often result in incomplete and/or highly fragmented metagenome-assembled genomes (MAGs), hampering in-depth genomics. Although Nanopore sequencing has increasingly been used in microbial metagenomics as long reads greatly improve the assembly quality of MAGs, the recommended DNA quantity usually exceeds the recoverable amount of DNA of environmental samples. Here, we evaluated lower-than-recommended DNA quantities for Nanopore library preparation by determining sequencing quality, community composition, assembly quality and recovery of MAGs. ResultsWe generated 27 Nanopore metagenomes using the commercially available ZYMO mock community and varied the amount of input DNA from 1000 ng (the recommended minimum) down to 1 ng in eight steps. The quality of the generated reads remained stable across all input levels. The read mapping accuracy, which reflects how well the reads match a known reference genome, was consistently high across all libraries. The relative abundance of the species in the metagenomes was stable down to input levels of 50 ng. High-quality MAGs (> 95% completeness, [≤] 5% contamination) could be recovered from metagenomes down to 35 ng of input material. When combined with publicly available Illumina reads for the mock community, Nanopore reads from input quantities as low as 1 ng improved the quality of hybrid assemblies. ConclusionOur results show that the recommended DNA amount for Nanopore library preparation can be substantially reduced without any adverse effects to genome recovery and still bolster hybrid assemblies when combined with short-read data. We posit that the results presented herein will enable studies to improve genome recovery from low-biomass environments, enhancing microbiome understanding.

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

Rates of primary production in groundwater rival those in oligotrophic marine systems

The terrestrial subsurface contains nearly all of Earths freshwater reserves1 and harbors upwards of 60% of our planets total prokaryotic biomass2,3. While genetic surveys suggest these organisms rely on in situ carbon fixation, rather than the translocation of photosynthetically derived organic carbon4-6, corroborating measurements of carbon fixation in the subsurface are absent. Using a novel ultra-low level 14C-labeling technique, we show that in situ carbon fixation rates in a carbonate aquifer reached 10% of the median rates measured in oligotrophic marine surface waters, and were up to six-fold greater than those observed in lower euphotic zone waters where deep chlorophyll levels peak. Empirical carbon fixation rates were substantiated by both nitrification and anammox rate data. Metagenomic analyses revealed a remarkable abundance of putative chemolithoautotrophic members of an uncharacterized order of Nitrospiria - the first representatives of this class expected to fix carbon via the Wood-Ljungdahl pathway. Based on these fixation rates, we extrapolate global primary production in carbonate groundwaters to be 0.11 Pg of carbon per year.

microbiology↗

bioRxiv2021

Genomic remnants of ancestral hydrogen and methane metabolism in Archaea drive anaerobic carbon cycling

Methane metabolism is among the hallmarks of Archaea, originating very early in their evolution. Other than its two main complexes, methyl-CoM reductase (Mcr) and tetrahydromethanopterin-CoM methyltransferase (Mtr), there exist other genes called "methanogenesis markers" that are believed to participate in methane metabolism. Many of them are Domains of Unknown Function. Here we show that these markers emerged together with methanogenesis. Even if Mcr is lost, the markers and Mtr can persist resulting in intermediate metabolic states related to the Wood-Ljungdahl pathway. Beyond the markers, the methanogenic ancestor was hydrogenotrophic, employing the anaplerotic hydrogenases Eha and Ehb. The selective pressures acting on Eha, Ehb, and Mtr partially depend on their subunits membrane association. Integrating the evolution of all these components, we propose that the ancestor of all methane metabolizers was an autotrophic H2/CO2 methanogen that could perhaps use methanol but not oxidize alkanes. Hydrogen-dependent methylotrophic methanogenesis has since emerged multiple times independently, both alongside a vertically inherited Mcr or from a patchwork of ancient transfers. Through their methanogenesis genomic remnants, Thorarchaeota and two newly reconstructed order-level lineages in Archaeoglobi and Bathyarchaeota act as metabolically versatile players in carbon cycling of anoxic environments across the globe.

microbiology↗

bioRxiv2021

The economical lifestyle of CPR bacteria in groundwater allows little preference for environmental drivers

The highly diverse Cand. Patescibacteria are predicted to have minimal biosynthetic and metabolic pathways, which hinders understanding of how their populations differentiate to environmental drivers or host organisms. Their metabolic traits to cope with oxidative stress are largely unknown. Here, we utilized genome-resolved metagenomics to investigate the adaptive genome repertoire of Patescibacteria in oxic and anoxic groundwaters, and to infer putative host ranges. Within six groundwater wells, Cand. Patescibacteria was the most dominant (up to 79%) super-phylum across 32 metagenomes obtained from sequential 0.2 and 0.1 {micro}m filtration. Of the reconstructed 1275 metagenome-assembled genomes (MAGs), 291 high-quality MAGs were classified as Cand. Patescibacteria. Cand. Paceibacteria and Cand. Microgenomates were enriched exclusively in the 0.1 {micro}m fractions, whereas candidate division ABY1 and Cand. Gracilibacteria were enriched in the 0.2 {micro}m fractions. Patescibacteria enriched in the smaller 0.1 {micro}m filter fractions had 22% smaller genomes, 13.4% lower replication measures, higher fraction of rod-shape determining proteins, and genomic features suggesting type IV pili mediated cell-cell attachments. Near-surface wells harbored Patescibacteria with higher replication rates than anoxic downstream wells characterized by longer water residence time. Except prevalence of superoxide dismutase genes in Patescibacteria MAGs enriched in oxic groundwaters (83%), no major metabolic or phylogenetic differences were observed based on oxygen concentrations. The most abundant Patescibacteria MAG in oxic groundwater encoded a nitrate transporter, nitrite reductase, and F-type ATPase, suggesting an alternative energy conservation mechanism. Patescibacteria consistently co-occurred with one another or with members of phyla Nanoarchaeota, Bacteroidota, Nitrospirota, and Omnitrophota. However, only 8% of MAGs showed highly significant one-to-one association, mostly with Omnitrophota. Genes coding for motility and transport functions in certain Patescibacteria were highly similar to genes from other phyla (Omnitrophota, Proteobacteria and Nanoarchaeota). Other than genes to cope with oxidative stress, we found little genomic evidence for niche adaptation of Patescibacteria to oxic or anoxic groundwaters. Given that we could detect specific host preference only for a few MAGs, we propose that the majority of Patescibacteria can attach to multiple hosts just long enough to loot or exchange supplies with an economic lifestyle of little preference for geochemical conditions.

microbiology↗

bioRxiv2020

Leave no stone unturned: The hidden potential of carbon and nitrogen cycling by novel, highly adapted Thaumarchaeota in the Atacama Desert hyperarid core

The hyperarid core of the Atacama Desert is an extremely harsh environment previously thought to be colonized by only a few heterotrophic bacterial species. In addition, carbon and nitrogen cycling in these highly oligotrophic ecosystems are poorly understood. Here we genomically resolved a novel genus of Thaumarchaeota, Ca. Nitrosodesertus, found below boulders of the Atacama hyperarid core, and used comparative genomics to analyze their pangenome and site-specific adaptations. Their genomes contain genes for ammonia oxidation and the 3-hydroxypropionate/4-hydroxybutyrate carbon fixation pathway, indicating a chemolithoautotrophic lifestyle. Ca. Nitrosodesertus possesses the capacity for tolerating extensive environmental stress highlighted by the presence of genes against oxidative stress, DNA damage and genes for the formation of biofilms. These features are likely responsible for their dominance in samples with extremely low water content across three different boulder fields and eight different boulders. Genome-specific adaptations of the genomes included the presence of additional genes for UV resistance, heavy metal transporters, multiple types of ATP synthases, and divergent genes for aquaporins. Our results suggest that Thaumarchaeota mediate important carbon and nitrogen cycling in the hyperarid core of the Atacama and are part of its continuous and indigenous microbiome.

genomics↗

bioRxiv2020

uBin - a manual refining tool for metagenomic bins designed for educational purposes

Resolving bacterial and archaeal genomes from metagenomes has revolutionized our understanding of Earths biomes, yet producing high quality genomes from assembled fragments has been an ever-standing problem. While automated binning software and their combination produce prokaryotic bins in high-throughput, their manual refinement has been slow and sometimes difficult. Here, we present uBin, a GUI-based, standalone bin refiner that runs on all major operating platforms and was specifically designed for educational purposes. When applied to the public CAMI dataset, refinement of bins was able to improve 78.9% of bins by decreasing their contamination. We also applied the bin refiner as a standalone binner to public metagenomes from the International Space Station and demonstrate the recovery of near-complete genomes, whose replication indices indicate active proliferation of microbes in Earths lower orbit. uBin is an easy to install software for bin refinement, binning of simple metagenomes and communication of metagenomic results to other scientists and in classrooms. The software is open source and available under https://github.com/ProbstLab/uBin.

genomics↗

bioRxiv2018

An archaeal symbiont-host association from the deep terrestrial subsurface

DPANN archaea have reduced metabolic capacities and are diverse and abundant in deep aquifer ecosystems, yet little is known about their interactions with other microorganisms that reside there. Here, we provide evidence for an archaeal host-symbiont association from a deep aquifer system at the Colorado Plateau (Utah, USA). The symbiont, Candidatus Huberiarchaeum crystalense, and its host, Ca. Altiarchaeum hamiconexum, show a highly significant co-occurrence pattern over 65 metagenome samples collected over six years. The physical association of the two organisms was confirmed with genome-informed fluorescence in situ hybridization depicting small cocci of Ca. H. crystalense attached to Ca. A. hamiconexum cells. Based on genomic information, Ca. H. crystalense has a similar metabolism as Nanoarchaeum equitans and potentially scavenges vitamins, sugars, nucleotides, and reduced redox-equivalents from its host. These results provide insight into host-symbiont interactions among members of two uncultivated archaeal phyla that thrive in a deep subsurface aquifer.

microbiology↗