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At least 19 recordsLinked to original sources
PubMed2026

Symbiosis reshapes metabolism of sulfate-reducing bacteria in gutless marine worms.

Sulfate-reducing bacteria (SRB) are widespread in marine and terrestrial environments, where they often form syntrophic associations with bacteria, archaea, and eukaryotes. Among the most intimate of these are multipartite symbioses in gutless marine oligochaete worms, which host SRB and sulfur-oxidizing endosymbionts that engage in a syntrophic exchange of sulfur compounds. Despite decades of research on free-living SRB, the metabolic traits that enable SRB to persist in symbiosis, and how these differ across hosts and environments, remain poorly understood. We show that a globally distributed clade of symbiotic SRB, which we named Candidatus Desulfoconcordia, has a conserved core metabolism that diverges from free-living relatives. Using comparative genomics and metaproteomics, we reveal that these endosymbionts retain key traits of SRB such as sulfate reduction, complete oxidation of acetate to CO2, amino acid degradation for nitrogen acquisition, and transport of essential nutrients. However, they exhibit a more oxygen-tolerant metabolism and lack typical nutrient-scavenging mechanisms of free-living SRB. One trait, the glyoxylate bypass, was consistently expressed in situ and may serve both in reactive oxygen species defence and in biomass generation. The expression of oxygen-tolerant pathways, coupled with the loss of nutrient-scavenging functions, indicate specialization to a host-associated, redox-fluctuating environment distinct from that of free-living SRB. The symbiont genomes are also larger than those of free-living relatives, contrasting with genome reduction in many endosymbionts and reinforcing the importance of metabolic versatility. Our findings provide a framework for understanding how metabolic flexibility enables SRB to persist in long-term multipartite symbioses across diverse marine ecosystems.

Symbiosis↗
PubMed2026

Microbial succession and assembly shaped by sulfur, spatial partitioning, and water flow in a volcanic acidic river of northern Patagonia.

Extreme acidic environments represent natural laboratories for investigating the mechanisms of microbial community assembly, yet the ecological processes structuring these communities remain incompletely understood. Here, we investigate how spatial partitioning, hydrodynamics, and colonization history shape microbial succession in a unique sulfur-rich, acidic river of volcanic origin in northern Patagonia. We combined 16S rRNA gene profiling and shotgun metagenomics with a multi-scale experimental framework encompassing water column fractionation and colonization assays under native and controlled conditions. Microbial diversity was strongly influenced by spatial fractionation, with free-living communities exhibiting higher richness and temporal variability than particle-associated assemblages. Water flow modulated community structure, increasing evenness in free-living fractions under high-flow conditions, but had limited impact on particle-attached communities. Colonization of sulfur-beads followed a structured successional trajectory, with autotrophic sulfur oxidizers dominating early stages and heterotrophs adapted to biofilm lifestyles increasing over time. Ex situ recolonization assays revealed strong priority effects, with initial colonizers determining successional trajectories. Turnover analyses revealed that the balance among stochastic and deterministic assembly processes shifted across communities with pronounced stochasticity in the water column and flow-dependent effects in free-living communities, while biofilm associated communities on sulfur-beads exhibited stronger contribution of deterministic selection. These ecological patterns were mirrored by functional differentiation, with gene enrichment analyses revealing adaptive signatures of substrate attachment and resource acquisition. By integrating fine-scale environmental variation with colonization dynamics, this study reveals how microscale habitat structure and temporal fluxes jointly modulate microbial community assembly rules, offering a nuanced framework to dissect ecological processes in extreme systems.

Sulfur↗
PubMed2023

Evolution of Orthonectida body plan.

Orthonectida is an enigmatic group of animals with still uncertain phylogenetic position. Orthonectids parasitize various marine invertebrates. Their life cycle comprises a parasitic plasmodium and free-living males and females. Sexual individuals develop inside the plasmodium; after egress from the host they copulate in the external environment, and the larva, which has developed inside the female infects a new host. In a series of studied orthonectid species simplification of free-living sexual individuals can be clearly traced. The number of longitudinal and transverse muscle fibers is gradually reduced. In the nervous system, simplification is even more pronounced. The number of neurons constituting the ganglion is dramatically reduced from 200 in Rhopalura ophiocomae to 4-6 in Intoshia variabili. The peripheral nervous system undergoes gradual simplification as well. The morphological simplification is accompanied with genome reduction. However, not only genes are lost from the genome, it also undergoes compactization ensured by extreme reduction of intergenic distances, short intron sizes, and elimination of repetitive elements. The main trend in orthonectid evolution is simplification and miniaturization of free-living sexual individuals coupled with reduction and compactization of the genome.

Animals↗
PubMed2026

Gut bacteria associated with an atherogenic TMAO-dietary pattern and choline-rich foods among aging women.

BACKGROUND AND AIMS: Choline can be metabolized by gut bacteria with a choline utilization gene, CutC, as identified through genome sequencing studies. This metabolism produces trimethylamine, the precursor to the atherosclerotic metabolite trimethylamine N-oxide (TMAO). Bacterial species involved in trimethylamine production in free-living humans have been under-investigated. We previously developed the TMAO dietary pattern (TMAO-DP), which is predictive of plasma TMAO and choline. We evaluated associations between the TMAO-DP, dietary choline, and choline-rich foods (fish, red meat, eggs) with the abundance of species with CutC. We also explored associations between the TMAO-DP and microbiome diversity. METHODS AND RESULTS: This cross-sectional analysis included 287 women (mean age = 79.6 years) from the Women's Health Initiative. Diet was assessed using a food frequency questionnaire. Stool samples were collected and the V3-V4 regions of the 16S ribosomal RNA were sequenced. Adjusted linear regression models evaluated associations between the TMAO-DP with the CLR-transformed abundance of species with CutC and with alpha-diversity indices. For beta-diversity, PERMANOVA examined measures of Aitchison distance within and between quartiles of the TMAO-DP. Associations between dietary choline and choline-rich foods with the abundance of species were evaluated using linear regression. The TMAO-DP was associated with Acidaminococcus intestini [Beta (SE): 0.23 (0.09), p-value = 0.035] and Desulfovibrio desulfuricans [Beta (SE): 0.16 (0.6), p = 0.035]. The TMAO-DP was not associated with alpha- or beta-diversity. CONCLUSION: This study provides evidence that Desulfovibrio desulfuricans and Acidaminococcus intestini, two species identified as having CutC by gene sequencing, may produce trimethylamine from diet in free-living women.

Humans↗
PubMed2026

Genomic contingence beneath ecological convergence: the tempo and mode of gene loss in parasitic bilaterians.

Parasitism has independently evolved hundreds of times among metazoans. Nonetheless, parasites have explored only a limited range of ecologies, and they display frequent convergence in morphological, behavioral, and life-history traits. Although gene loss in particular parasitic species has been documented, it is not known if gene loss converges along the same lines as these other traits. To test for convergent gene loss, we characterized the housekeeping, regulatory, and DNA-repair complements of 48 bilaterian species, including 20 parasites belonging to 6 different bilaterian phyla. We found that different parasitic strategies do not display characteristic tempos or modes of gene loss. Further, the accelerated rates of gene loss seen in some parasites were almost always shared with their free-living relatives, indicating that the increased rate of loss preceded the rise of parasitism. Therefore, the convergent ecological strategies and adaptations that have arisen in distantly related parasitic lineages overlay contingent gene losses, which largely reflect their phylogenetic history. These results have important implications for how ecologists and evolutionary biologists should model the acquisition of parasitism, especially regarding the long-held assumption that reversion from a parasitic to a free-living state is impossible.

Animals↗
PubMed2025

Persistent gaps and errors in reference databases impede ecologically meaningful taxonomy assignments in 18S rRNA studies: a case study of terrestrial and marine nematodes.

In metabarcoding studies, Linnaean taxonomy assignments of Operational Taxonomic Units (OTUs) or Amplicon Sequence Variants (ASVs) underpin many downstream bioinformatics analyses and ecological interpretations of environmental DNA (eDNA) datasets. However, public molecular databases (i.e., SILVA, EUKARYOME, BOLD) for most microbial metazoan phyla (nematodes, tardigrades, kinorhynchs, etc.) are sparsely populated, negatively impacting our ability to assign ecologically meaningful taxonomy to these understudied groups. Additionally, the choice of bioinformatics parameters and computational algorithms can further impact the accuracy of eDNA taxonomy assignments. Here, we use two in-silico datasets to show that taxonomy assignments using the 18S rRNA gene can be dramatically improved by curating Linnaean taxonomy strings associated with each reference sequence and closing phylogenetic gaps by improving taxon sampling. Using free-living nematodes as a case study, we applied two commonly used taxonomy assignment algorithms (BLAST+ and the QIIME2 Naïve Bayes classifier) across six iterations of the SILVA 138 reference database to evaluate the precision and accuracy of taxonomy assignments. The BLAST+ top hit with a 90% sequence similarity cutoff often returned the highest percentage of correctly assigned taxonomy at the genus level, and the QIIME2 Naïve Bayes classifier performed similarly well when paired with a reference database containing corrected taxonomy strings. Our results highlight the urgent need for phylogenetically-informed expansions of public reference databases (encompassing both genomes and common gene markers), focused on poorly sampled lineages which are now robustly recovered via eDNA metabarcoding approaches. Additional taxonomy curation efforts should be applied to popular reference databases such as SILVA, and taxon sampling could be rapidly improved by more frequent incorporation of newly published GenBank sequences linked to genus and/or species level identifications.

18S rRNA metabarcoding↗
PubMed2026

Twenty-Five Years of the Environmental Stress Response and the Enduring Power of Yeast in Stress Biology.

All organisms must be able to sense and respond to adverse environments, especially those that threaten cellular integrity. The age of genomics clarified the breadth and specificity of cellular stress responses, including in free-living microbes directly exposed to a changing environment. The environmental stress response (ESR) in Saccharomyces cerevisiae was among the first responses defined at the transcriptome-wide level as a common program triggered by diverse types of stress. Since its original publication over 25 years ago, many studies have explored the role, regulation, and evolution of the ESR and underlying principles of stress defense. This perspective reviews the history of the ESR, recent insights and perspectives into its purpose and regulation, and remaining questions in stress biology primed for the power of yeast experimentation.

Saccharomyces cerevisiae↗
PubMed2026

Ecological momentary assessment studies on food craving among healthy adults: A systematic review.

Ecological Momentary Assessment (EMA) can capture the dynamic nature of food craving in free-living conditions, addressing limitations of laboratory and retrospective reporting methods. This systematic review synthesized findings from EMA studies to characterize 1) methodological features, 2) the temporal dynamics of food craving, and 3) the relationship between craving and eating behaviors. A systematic search of PubMed and PsycINFO databases was conducted following PRISMA guidelines. The review included 23 studies that utilized EMA designs to assess food craving repeatedly in daily life among healthy adults. Most studies employed EMA protocols that prompted participants to respond at pre-specified time points and utilized single-item craving measures. Most craving measures (71%) lacked specificity regarding the type of food craved. Results revealed a consistent positive within-person association between hunger and food craving. Conversely, associations between stress/negative affect and craving were inconsistent, varying by individual traits and context. Momentary food craving appeared to predict subsequent eating outcomes. Evidence suggested food craving may be a dynamic, transient state that co-fluctuates with hunger, functioning as a proximal antecedent to food intake. However, reliance on non-specific food craving measures and EMA protocols prompting at fixed schedules limits the granular understanding of craving mechanisms. Future research requires refining food craving measurement and incorporating randomized prompting within predefined windows, or participant-initiated sampling triggered by specific events (e.g., eating occasion), to better characterize food craving dynamics in relation to eating behaviors.

Humans↗
PubMed2026

A novel jakobid genus from the soil of an indoor plant.

Jakobids are a group of free-living heterotrophic flagellates that hold a key phylogenetic position for understanding early eukaryote evolution and are particularly notable for their gene-rich, bacteria-like mitochondrial genomes. Although the number of formally described species is small, jakobids are frequently detected in anoxic marine habitats. However, their edaphic diversity remains unexplored, with the few documented isolations from soil over the past two decades, each yielding a new genus. Here, we describe a novel jakobid, Celatomonas quasimodo gen. et sp. nov., isolated from commercial potting soil used for cultivating indoor plants. The organism was characterised by light and scanning electron microscopy, and its phylogenetic position was inferred using 18S rRNA gene phylogenetic analysis. While exhibiting typical jakobid features, the cells adopt a highly unusual curved-triangular morphology during division, which has not been reported for any other jakobid. Phylogenetic analysis placed C. quasimodo as the firmly supported sister lineage of Moramonas marocensis within the family Moramonadidae (suborder Histionina). Despite this close affinity, the two taxa present a level of 18S rRNA gene divergence comparable to that between already recognised genera of Moramonadidae. Together, these data support the recognition of Celatomonas quasimodo as a new genus and species within Moramonadidae. Furthermore, screening of soil environmental DNA datasets revealed the presence of multiple novel jakobid lineages, alongside a novel jakobid clade (JENV-1) of uncertain phylogenetic position from equatorial environments. This newly described jakobid genus provides a valuable model for future comparative studies of cellular ultrastructure and the evolution of jakobid mitochondrial genomes. Combined with the environmental DNA screening results, our findings underscore the importance of soil habitats as reservoirs of unexplored eukaryotic diversity and provide new insights into jakobid systematics.

Phylogeny↗
PubMed2026

Heavy-metal stress shapes habitat-specific microbial survival strategies in estuarine environments.

Estuarine ecosystems face increasing heavy metal pollution from rapid urbanization and industrialization, yet the microbial adaptive strategies to multiple metal stressors across different habitats remain poorly understood. This study investigated the diversity and composition of bacterial and fungal communities across free-living (FL), particle-attached (PA), and sediment (SE) fractions from three estuaries with varying heavy metal contamination, and further investigated functional adaptations of bacterial communities. High-throughput amplicon sequencing revealed habitat-specific communities, with SE hosting the highest alpha diversity and enrichment of metal-resistant genera such as Woeseia and Sva1033. Environmental filtering, particularly by Zn, was the dominant driver shaping bacterial assemblages across all habitats, whereas fungal communities displayed greater stochastic assembly patterns. Analysis of 44 high-quality bacterial metagenome-assembled genomes (MAGs) revealed diverse metal resistance genes (cusA, znuB, and zntA), along with enriched metabolic pathways for carbon, nitrogen, and sulfur cycling. Notably, both active efflux/oxidative stress defense and indirect immobilization mechanisms were observed across all habitats, but their relative importance differed: FL and PA communities exhibited a greater reliance on active metal efflux (czcAB) and oxidative stress defense (trxAB) to maintain intracellular homeostasis, whereas SE communities displayed a stronger genomic potential for sulfate reduction (dsrAB) that may contribute to metal immobilization through sulfide precipitation. This metabolic partitioning highlights the complementary roles of different habitats in mediating metal toxicity and biogeochemical cycling, providing new insights into microbial resilience in polluted estuaries and underscoring the urgency of addressing heavy-metal contamination in these critical ecosystems.

Estuaries↗
PubMed2024

Bacterial lifestyle shapes pangenomes.

Pangenomes vary across bacteria. Some species have fluid pangenomes, with a high proportion of genes varying between individual genomes. Other species have less fluid pangenomes, with different genomes tending to contain the same genes. Two main hypotheses have been suggested to explain this variation: differences in species' bacterial lifestyle and effective population size. However, previous studies have not been able to test between these hypotheses because the different features of lifestyle and effective population size are highly correlated with each other, and phylogenetically conserved, making it hard to disentangle their relative importance. We used phylogeny-based analyses, across 126 bacterial species, to tease apart the causal role of different factors. We found that pangenome fluidity was lower in i) host-associated compared with free-living species and ii) host-associated species that are obligately dependent on a host, live inside cells, and are more pathogenic and less motile. In contrast, we found no support for the competing hypothesis that larger effective population sizes lead to more fluid pangenomes. Effective population size appears to correlate with pangenome variation because it is also driven by bacterial lifestyle, rather than because of a causal relationship.

Genome, Bacterial↗
PubMed2025

The early evolution of the glycolytic pathway from autotrophic origins to glycogen and back.

Glycolysis stops where gluconeogenesis starts-at pyruvate, the central metabolite of biosynthesis. The early history of carbon metabolism is preserved in archaeal and bacterial enzymes for glucose synthesis and breakdown. Here, we summarize the distribution and phylogeny of enzymes involved in glycolysis, gluconeogenesis, and glycogen metabolism from genomes of cultured prokaryotes. The presence of glycolytic pathways in H2-dependent chemolithoautotrophs, including methanogens, which cannot grow on exogenous glucose, correlates with their use of glycogen for intracellular carbon storage. Glycogen synthesis and gluconeogenesis are universal among prokaryotes, but glycolysis is not, indicating that the enzymatic conversions of glycolysis arose in the gluconeogenic direction encompassing three phases: (1) an autotrophic origin from H2 and CO2 to pyruvate and triosephosphate (trunk glycolysis) fulfilling basic amino acid and cofactor synthesis in the last universal common ancestor, (2) from triosephosphate to glucose supplying cell wall (murein and pseudomurein) and nucleic acid biosynthetic requirements in the first free-living autotrophs, also giving rise to intracellular carbon reserves (glycogen), followed by (3) diversification and transfer of enzymes for glycogen-mobilizing glycolytic routes. An autotrophic origin of trunk glycolysis followed by glycogen-dependent origin of glucose utilization account for conservation, distribution, and diversity of enzymes observed in microbial sugar phosphate pathways.

Glycolysis↗
PubMed2025

Pseudoalteromonas is a novel symbiont of marine invertebrates that exhibits broad patterns of phylosymbiosis.

Despite growing insights into the composition of marine invertebrate microbiomes, our understanding of their ecological and evolutionary patterns remains poor, owing to limited sampling depth and low-resolution datasets. Previous studies have provided mixed results when evaluating patterns of phylosymbiosis between marine invertebrates and marine bacteria. Here, we investigated potential animal-microbe symbioses in Pseudoalteromonas, an overlooked bacterial genus consistently identified as a core microbiome taxon in diverse invertebrates. Using a pangenomic analysis of 236 free-living and invertebrate-associated bacterial strains (including two new nematode-associated isolates generated in this study), we confirm that Pseudoalteromonas is a novel symbiont with substantial evidence of phylosymbiosis across at least three marine invertebrate phyla (e.g., Nematoda, Mollusca, and Cnidaria). Patterns of symbiosis were consistent irrespective of geography (including in Antarctica), with FISH images from nematodes indicating that bacterial symbionts form biofilms in the mouth and esophagus. The evolutionary history of Pseudoalteromonas is marked by substantial host-switching and lifestyle transitions, and host-associated genomes suggest that these bacteria are facultative symbionts involved in nutritional mutualisms. In marine environments, we hypothesize that horizontally-acquired symbionts may have co-evolved with invertebrates, using host mucus as a physical niche and food source, while providing their animal hosts with Vitamin B, amino acids, and bioavailable carbon compounds in return.

Marine Invertebrates↗
PubMed2023

Emerging trends in the study of spiralian larvae.

Many animals undergo indirect development, where their embryogenesis produces an intermediate life stage, or larva, that is often free-living and later metamorphoses into an adult. As their adult counterparts, larvae can have unique and diverse morphologies and occupy various ecological niches. Given their broad phylogenetic distribution, larvae have been central to hypotheses about animal evolution. However, the evolution of these intermediate forms and the developmental mechanisms diversifying animal life cycles are still debated. This review focuses on Spiralia, a large and diverse clade of bilaterally symmetrical animals with a fascinating array of larval forms, most notably the archetypical trochophore larva. We explore how classic research and modern advances have improved our understanding of spiralian larvae, their development, and evolution. Specifically, we examine three morphological features of spiralian larvae: the anterior neural system, the ciliary bands, and the posterior hyposphere. The combination of molecular and developmental evidence with modern high-throughput techniques, such as comparative genomics, single-cell transcriptomics, and epigenomics, is a promising strategy that will lead to new testable hypotheses about the mechanisms behind the evolution of larvae and life cycles in Spiralia and animals in general. We predict that the increasing number of available genomes for Spiralia and the optimization of genome-wide and single-cell approaches will unlock the study of many emerging spiralian taxa, transforming our views of the evolution of this animal group and their larvae.

Animals↗
PubMed2025

Contrasting Genomic Responses of Hydrothermal Vent Animals and Their Symbionts to Population Decline After the Hunga Volcanic Eruption.

Genetic bottlenecks are evolutionary events that reduce the effective size and diversity of natural populations, often limiting a population's ability to adapt to environmental change. Given the accelerating human impact on ecosystems worldwide, understanding how populations evolve after a genetic bottleneck is becoming increasingly important for species conservation. Ash deposits from the 2022 Hunga volcanic eruption in the Southwest Pacific led to a drastic decline of animal symbioses associated with hydrothermal vents in this region, allowing insights into the effects of population bottlenecks in the deep sea. Here, we applied metagenomic sequencing to pre- and post-eruption samples of mollusc-microbial symbioses from the Lau Basin to investigate patterns of genetic variation and effective population size. Our data indicate that animal host populations currently show only small changes in genome-wide diversity but in most cases experienced a long-term decline in effective size that was likely intensified by the volcanic impact. By contrast, host-associated symbiont populations exhibited a notable decrease in genomic variation, including potential loss of certain habitat-specific strains. However, detection of environmental sequences resembling mollusc symbionts suggests that lost host-associated symbiont diversity might be recovered from the free-living symbiont pool. The differences between host and symbiont populations might be related to their contrasting genetic structures and pre-existing levels of connectivity, although the full extent of population bottlenecks in the host animals might only be recognisable after a few generations. These results add to our understanding of the evolutionary dynamics of animal-microbe populations following a natural disturbance and help assess their resilience to both natural and anthropogenic impacts.

Animals↗
PubMed2025

From Worms to Tumors: Conserved Strategies of Cellular Arrest and Survival Governing Dormancy.

The recurrence of metastatic lesions months to years after the treatment of primary cancers remains a major contributor to cancer-related mortality, highlighting the need to better understand the mechanisms that govern dormancy and dormancy reawakening. A major hurdle is the lack of adequate in vitro and in vivo models to dissect the complex cascades that trigger tumor cell dissemination, adoption of the dormant state, or tumor cell outgrowth in the new metastatic microenvironmental niche. However, many organisms use dormancy to survive stressful environments or periods of nutrient deprivation. Of these, the dauer state of the free-living nematode Caenorhabditis elegans has unparalleled characterization. In this study, we discuss the remarkable physiologic, signaling, genomic, and metabolic similarities between dormant cancer cells and C. elegans dauers, arguing for the use of dauers as a facile model to help dissect dormancy and reawakening pathways in cancer cells.

Animals↗
PubMed2026

Convergent evolution of intestinal lineages in the phylum Methanobacteriota.

BACKGROUND: Representatives of the phylum Methanobacteriota occur in various anoxic environments, but only members of the genera Methanosphaera and Methanobrevibacter exclusively colonize the digestive tract of animals. Recent phylogenomic analyses revealed that the genus Methanobrevibacter, which harbors the majority of the intestinal species, is severely underclassified and represents a family-level taxon, "Methanobrevibacteraceae", that evolved entirely in the digestive tract of animals. RESULTS: Comparative genome analysis of 158 species of Methanobacteriota, including uncultured representatives in the Genome Taxonomy Database (GTDB), demonstrated that the intestinal lineages are clearly separated from the remaining members of the phylum. They differ from the non-intestinal lineages in genome size, GC content, coding density, an increased number of pseudogenes and adhesin-like proteins, and show numerous adaptations to the copiotrophic gut environment. A decreased biosynthetic potential led to a dependence on other community members and limits the dispersal of intestinal species into other habitats, which is reflected in coevolutionary patterns with their major host groups among arthropods, ungulates, and primates. Certain lineages even engaged in symbiotic associations with intestinal protists, presumably benefiting from the H2 produced by the hydrogenosomes of their anaerobic hosts. CONCLUSIONS: Our results reveal that the transition of free-living Methanobacteriota to a host-associated lifestyle involves the same genomic changes that were previously recognized in gut bacteria and bacterial endosymbionts of protists, reflecting resemblances between the two prokaryotic domains that are caused by evolutionary convergence in similar environments.

Animals↗