Biology subjects

Leao, P.

Publications and source records attributed to Leao, P..

10 recordsLinked to original sources

bioRxiv2026

ArchaeaHQ: A Curated Reference Database of Archaeal Genomes

Archaea have proven to be major players in biogeochemical cycles across diverse ecosystems, yet we still see an underrepresentation of archaeal genomes in the datasets used by popular computational biology tools. Here we present ArchaeaHQ, a quality-controlled, systematically curated reference database of 21,644 archaeal genomes compiled initially from 35,993 assemblies from all four archaeal kingdoms retrieved from NCBI: Methanobacteriati (Euryarchaeota), Thermoproteati (TACK), Nanobdellati (DPANN), and Promethearchaeati (Asgard). All genomes in the database passed standardized quality control, requiring [≥]70% completeness and [≤]10% contamination. A total of 44.2% of genomes in ArchaeaHQ achieved [≥]90% completeness, while 93.1% exhibited [≤]5% contamination. ArchaeaHQ comprises 16,199 metagenome-assembled genomes (MAGs; 74.8%) and 5,445 isolate genomes (25.2%). Approximately 75% of MAGs are assigned to 17 ecologically meaningful categories based on sampling origin, and around 65% of genomes include geographic metadata. ArchaeaHQ is available at https://doi.org/10.6084/m9.figshare.32266599 and provides an analysis-ready reference set for metagenomic classification, biogeochemical and ecological studies, comparative genomics, and development of archaeal-specific bioinformatic tools. Impact StatementArchaea are key drivers of the global carbon, nitrogen and methane cycles, yet their genomes remain underrepresented and inconsistently curated in the public databases that power modern computational biology tools. We present ArchaeaHQ, a quality-controlled, systematically curated reference set of 21,644 archaeal genomes spanning all four archaeal kingdoms, each passing standardized completeness and contamination thresholds and enriched with environmental and geographic metadata. By providing an analysis-ready, downloadable resource compatible with standard pipelines, ArchaeaHQ fits the gap between taxonomy-focused frameworks and unfiltered genome archives supporting metagenomic classification, biogeochemical and ecological studies, comparative genomics, and the development of archaeal-specific bioinformatic tools.

microbiology↗

bioRxiv2026

Activation-independent capture of free fatty acids at the bacterial cell envelope by BrtB

Fatty acids (FAs) are key metabolites in living organisms, shaping membrane architecture and helping cellular acclimatization to changing conditions. Bacteria synthesize FA de novo but can also reclaim them from membrane lipids or uptake them from the environment, usually converting free fatty acids (FFAs) into activated FAs that can then be further metabolized. In cyanobacteria, it is the acyl-acyl carrier protein synthetase (Aas) that activates exogenous FFAs. Yet, the cyanobacterial enzyme BrtB was recently shown to esterify, in vitro, FFAs directly onto abundant chlorinated glycolipids (bartolosides), generating bartoloside fatty acid esters (B-FAs). Whether this chemistry operates in vivo, where it occurs, and what its implications are for cell physiology has remained unclear. Here we show that in the cyanobacterium Synechocystis salina LEGE 06099, BrtB captures FFAs at the cell envelope without prior activation to generate B-FAs. We found that supplemented FFAs were converted into B-FAs within minutes. Strikingly, this response occurred with minimal changes in gene expression and little alteration of the extracellular proteome, consistent with a pathway already in place. Additionally, we observed that B-FAs can further be hydrolyzed into hydroxybartolosides - the levels of the latter metabolites increase in response to FA supply, suggesting a transient sequestration of FFA. Our results demonstrate that activation of FFA is not the only route to their cellular incorporation and identify a specialized-metabolite pathway that captures exogenous FFAs at the cyanobacterial cell envelope.

microbiology↗

bioRxiv2026

Coastal sediments maintain potential for N2O cycling under seasonally varying redox conditions

Coastal eutrophication can lead to deoxygenation and sulfide accumulation in sediments, which could strongly impact the dynamics of the potent greenhouse gas nitrous oxide (N2O). Here, we investigated the effects of oxygen (O2) and sulfide on microbial N2O production and consumption in surface sediments of a seasonally euxinic (anoxic and sulfidic) coastal basin. In spring, these surface sediments are oxygenated, while they are highly sulfidic during stratification of the water column in summer. During oxygenated spring conditions, rapid depletion of the substrates O2 and nitrate (NO3-) in the surface sediment limited net in situ N2O production, despite potential for nitrification and for N2O production through incomplete denitrification as observed in batch incubations. Based on metagenome and metatranscriptome analyses the N2O-consuming microbial community was shown to be highly diverse and dominated by clade II nosZ-possessing Flavobacteriia. Assessing the summer sulfidic conditions in surface sediments via batch incubations, we found that moderate sulfide concentrations (0.2-1 mM) enhanced N2O consumption, whereas high concentrations (4 mM) inhibited all steps of denitrification. These findings highlight the redox controls on N2O dynamics, by indicating that coastal sediments can maintain significant N2O turnover potential despite substrate limitations and elevated sulfide concentrations. Consequently, ecosystem restoration strategies that alter O2, NO3- and sulfide availability may fundamentally impact coastal N2O budgets.

microbiology↗

bioRxiv2025

Mini-bacterioferritins: Structural insight into a new type of ferritin-like protein from an anaerobic methane-oxidising archaeon

Ferritins are ubiquitous among life forms, as they are essential for iron homeostasis. Here, we unveiled a novel member of the ferritin family, baptised mini-bacterioferritin. The characterised mini-bacterioferritin was isolated from a microbial enrichment dominated by the methanotrophic archaeon Candidatus Methanoperedens BLZ2. Its atomic resolution crystal structure reveals a 12-mer assembly with a diiron ferroxidase centre located within a four-helix bundle. Redox cycling experiments on protein crystals reveal a shift in iron position at the active site, which follows the established ferritin catalytic cycle. The 12-mer sphere-like structure harboured six Fe-coproporphyrin III ligands, positioned at the interdimeric interface, a characteristic previously only found in 24-mer bacterioferritins. Phylogenetics, together with structure predictions of closely related proteins, revealed that mini-bacterioferritins form a new clade within the ferritin family that might conserve ancestral traits. Future research will need to investigate the physiological roles of these enzymes, which were unsuspectingly widely distributed among prokaryotes. TeaserA novel ferritin family, the heme-binding mini-bacterioferritin, assembles as a dodecamer and is widely distributed among microbes.

biochemistry↗

bioRxiv2024

Methanotrophic flexibility of Ca. Methanoperedens and its interactions with sulfate-1 reducing bacteria in the sediment of meromictic Lake Cadagno

The greenhouse gas methane is an important contributor to global warming, with freshwater sediments representing important potential methane sources. Anaerobic methane-oxidizing archaea mitigate methane release into the atmosphere by coupling the oxidation of methane to the reduction of extracellular electron acceptors or through interspecies electron transfer with microbial partners. Understanding their metabolic flexibility and microbial interactions is crucial to assess their role in global methane cycling. Here, we investigated anoxic sediments of the meromictic freshwater Lake Cadagno (Switzerland), where Ca. Methanoperedens and sulfate-reducing bacteria co-occur, with metagenomics and long-term incubations. Incubations were performed with different electron acceptors, revealing that manganese oxides supported highest CH4 oxidation potential but enriched for Ca. Methanoperedens phylotypes that were hardly present in the inoculum. Combining data from the inoculum and incubations, we obtained five Ca. Methanoperedens genomes, each harboring different extracellular electron transfer pathways. In a reconstructed Desulfobacterota QYQD01 genome we observed large multi-heme cytochromes, type IV pili, and a putative loss of hydrogenases, suggesting facultative syntrophic interactions with Ca. Methanoperedens. We also screened for putative extrachromosomal elements in the Ca. Methanoperedens genomes, including BORGs. This research deepens our understanding of the metabolic flexibility and potential interspecific interactions of Ca. Methanoperedens in freshwater lakes.

microbiology↗

bioRxiv2024

Oxygen metabolism in descendants of the archaeal-eukaryotic ancestor

Asgard archaea were pivotal in the origin of complex cellular life. Hodarchaeales (Asgardarchaeota class Heimdallarchaeia) were recently shown to be the closest relatives of eukaryotes. However, limited sampling of these archaea constrains our understanding of their ecology and evolution1-3, including their anticipated role in eukaryogenesis. Here, we nearly double the number of Asgardarchaeota metagenome-assembled genomes (MAGs) to 869, including 136 new Heimdallarchaeia (49 Hodarchaeales) and several novel lineages. Examining global distribution revealed Hodarcheales are primarily found in coastal marine sediments. Detailed analysis of their metabolic capabilities revealed guilds of Heimdallarchaeia are distinct from other Asgardarchaeota. These archaea encode hallmarks of aerobic eukaryotes, including electron transport chain complexes (III and IV), biosynthesis of heme, and response to reactive oxygen species (ROS). The predicted structural architecture of Heimdallarchaeia membrane-bound hydrogenases includes additional Complex-I-like subunits potentially increasing the proton motive force and ATP synthesis. Heimdallarchaeia genomes encode CoxD, which regulates the electron transport chain (ETC) in eukaryotes. Thus, key hallmarks for aerobic respiration may have been present in the Asgard-eukaryotic ancestor. Moreover, we found that Heimdallarchaeia is present in a variety of oxic marine environments. This expanded diversity reveals these Archaea likely conferred energetic advantages during early stages of eukaryogenesis, fueling cellular complexity.

microbiology↗

bioRxiv2024

Genetic elements and defense systems drive diversification and evolution in Asgard archaea

Asgard Archaea are of great interest as the progenitors of Eukaryotes, but little is known about the mobile genetic elements (MGEs) that may shape their ongoing evolution. Here, we describe MGEs that replicate in Atabeyarchaeia, wetland Asgard archaea phylum represented by two complete genomes. We used soil depth-resolved population metagenomic datasets to track 18 MGEs for which genome structures were defined and precise chromosome integration sites could be identified for confident host linkage. Additionally, we identified a complete 20.67 kilobase pair (kbp) circular plasmid (the first reported for Asgard archaea) and two groups of viruses linked to Atabeyarchaeia, via CRISPR spacer targeting. Closely related 40 kbp viruses possess a hypervariable genomic region encoding combinations of specific genes for small cysteine-rich proteins structurally similar to restriction-homing endonucleases. One 10.9 kbp circularizable plasmid-like MGE integrates genomically into an Atabeyarchaeia chromosome and has a 2.5 kbp circularizable element integrated within it. The 10.9 kbp MGE encodes a highly expressed methylase with a sequence specificity matching an active methylation motif identified by PacBio sequencing. Restriction-modification of Atabeyarchaeia differs from that of another coexisting Asgard archaea Freyarchaeia which has few identified MGEs but possesses diverse defense mechanisms, including DISARM and Hachiman not found in Atabeyarchaeia. Overall, defense systems and methylation mechanisms of Asgard archaea likely modulate their interactions with MGEs, and integration/excision and copy number variation of MGEs in turn enable host genetic versatility.

microbiology↗

bioRxiv2023

Asgard archaea defense systems and their roles in the origin of immunity in eukaryotes

Immune systems are integral to survival against viral infection. Recently, dozens of new antiviral systems have been characterized in bacteria1. Some of these systems are present in eukaryotes and appear to have originated in prokaryotes. However, little is known about these defense mechanisms in archaea. Here, we identified 2,610 complete defense systems in archaea related to eukaryotes, the Asgardarchaeota2. These comprise 89 unique systems, including argonaute, NLR, mokosh, viperin, lassamu, and CBASS. Asgard viperin (asVip) and argonaute (asAgo) proteins are present at high frequencies compared to bacteria and have structural homology to eukaryotes. Phylogenetic analyses revealed asVips are ancestral eukaryotic proteins. Heterologous expression of asVips in bacteria, including the lineage closest to eukaryotes, Hodarchaeales, showed anti-phage activity. Eukaryotic- and bacterial-argonaute proteins appear to have originated in Asgardarchaeota and preserve ancient structural characteristics. asAgos have argonaute-PIWI domains which are key components of the RNA interference (RNAi) in eukaryotes. Characterization of hundreds of defense systems in the Asgardarchaeota revealed these archaea played important roles in the innovation of viral protection in eukaryotes. Given their relationship to eukaryotes, these defense systems may have applications in biomedicine and biotechnology.

microbiology↗

bioRxiv2022

Detection of interphylum transfers of the magnetosome gene cluster in magnetotactic bacteria

Magnetosome synthesis in magnetotactic bacteria (MTB) is regarded as a very ancient evolutionary process that dates back to deep-branching phyla. MTB belonging to one of such phyla, Nitrospirota, contain the classical genes for the magnetosome synthesis (e.g., mam, mms) and man genes, which were considered to be specific for this group. However, the recent discovery of man genes in MTB from the Thermodesulfobacteriota phylum has raised several questions about the inheritance of these genes in MTB. In this work, three new man genes containing MTB genomes affiliated with Nitrospirota and Thermodesulfobacteriota, were obtained. By applying reconciliation with these and the previously published MTB genomes, we demonstrate that the last common ancestor of all Nitrospirota was most likely not magnetotactic as assumed previously. Instead, our findings suggest that the genes for magnetosome synthesis were transmitted to the phylum Nitrospirota by horizontal gene transfer (HGT), which is the first case of the interphylum transfer of magnetosome genes detected to date. Furthermore, we provide evidence for the HGT of magnetosome genes from the Magnetobacteriaceae to the Dissulfurispiraceae family within Nitrospirota. Thus, our results imply a more significant role of HGT in the MTB evolution than deemed before and challenge the hypothesis of the ancient origin of magnetosome synthesis.

microbiology↗

bioRxiv2019

Characterizing of novel magnetotactic bacteria using a combination of magnetic column separation (MTB-CoSe) and mamK-specific primers

According to 16S rRNA gene- or genome-based phylogeny, magnetotactic bacteria (MTB) belong to diverse taxonomic groups. Here we analyzed the diversity of MTB in a sample taken from the freshwater lake Beloe Bordukovskoe near Moscow, Russia, by using molecular identification based on sequencing of the 16S rRNA gene and mamK, a specific marker gene for these bacteria. A protein encoded by the mamK gene is involved in magnetosome chain arrangement inside the cell. As a result, six operational taxonomic units (OTUs) of MTB were identified. Among them, OTUs affiliated with the phylum Nitrospirae were predominant. Ca. Etaproteobacteria and Alphaproteobacteria represented the minor groups of MTB. We also identified a novel MTB belonging to the family Syntrophaceae of the Deltaproteobacteria class. Using a combination of fluorescence and transmission electron microscopy, the bacteria belonging to these new MTB groups were visualized. Electron microscopy revealed that Syntrophaceae MTB were rod-shaped and synthesized elongated magnetosomes, arranged as a disorganized cluster. Among the Nitrospirae group, two groups with vibrioid cell shape and one group of ovoid-shaped bacteria were identified, all of which had elongated magnetosome crystals consisting of magnetite.

microbiology↗