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At least 19 recordsLinked to original sources
PubMed2025

Anaerobic breviate protist survival in microcosms depends on microbiome metabolic function.

Anoxic and hypoxic environments serve as habitats for diverse microorganisms, including unicellular eukaryotes (protists) and prokaryotes. To thrive in low-oxygen environments, protists and prokaryotes often establish specialized metabolic cross-feeding associations, such as syntrophy, with other microorganisms. Previous studies show that the breviate protist Lenisia limosa engages in a mutualistic association with a denitrifying Arcobacter bacterium based on hydrogen exchange. Here, we investigate if the ability to form metabolic interactions is conserved in other breviates by studying five diverse breviate microcosms and their associated bacteria. We show that five laboratory microcosms of marine breviates live with multiple hydrogen-consuming prokaryotes that are predicted to have different preferences for terminal electron acceptors using genome-resolved metagenomics. Protist growth rates vary in response to electron acceptors depending on the make-up of the prokaryotic community. We find that the metabolic capabilities of the bacteria and not their taxonomic affiliations determine protist growth and survival and present new potential protist-interacting bacteria from the Arcobacteraceae, Desulfovibrionaceae, and Terasakiella lineages. This investigation uncovers potential nitrogen and sulfur cycling pathways within these bacterial populations, hinting at their roles in syntrophic interactions with the protists via hydrogen exchange.

Anaerobiosis↗
PubMed2025

Modes and mechanisms for the inheritance of mitochondria and plastids in pathogenic protists.

Pathogenic protists are responsible for many diseases that significantly impact human and animal health across the globe. Almost all protists possess mitochondria or mitochondrion-related organelles, and many contain plastids. These endosymbiotic organelles are crucial to survival and provide well-validated and widely utilised drug targets in parasitic protists such as Plasmodium and Toxoplasma. However, mutations within the organellar genomes of mitochondria and plastids can lead to drug resistance. Such mutations ultimately challenge our ability to control and eradicate the diseases caused by these pathogenic protists. Therefore, it is important to understand how organellar genomes, and the resistance mutations encoded within them, are inherited during protist sexual reproduction and how this may impact the spread of drug resistance and future therapeutic approaches to target these organelles. In this review, we detail what is known about mitochondrial and plastid inheritance during sexual reproduction across different pathogenic protists, often turning to their better studied, nonpathogenic relatives for insight.

Plastids↗
PubMed2025

Subcellular proteomics of the protist Paradiplonema papillatum reveals the digestive capacity of the cell membrane and the plasticity of peroxisomes across euglenozoans.

Diplonemids are among the most diverse and abundant protists in the deep ocean, have extremely complex and ancient cellular systems, and exhibit unique metabolic capacities. Despite this, we know very little about this major group of eukaryotes. To establish a model organism for comprehensive investigation, we performed subcellular proteomics on Paradiplonema papillatum and localized 4,870 proteins to 22 cellular compartments. We additionally confirmed the predicted location of several proteins by epitope tagging and fluorescence microscopy. To probe the metabolic capacities of P. papillatum, we explored the proteins predicted to the cell membrane compartment in our subcellular proteomics dataset. Our data revealed an accumulation of many carbohydrate-degrading enzymes (CDZymes). Our predictions suggest that these CDZymes are exposed to the extracellular space, supporting proposals that diplonemids may specialize in breaking down carbohydrates in plant and algal cell walls. Further exploration of carbohydrate metabolism revealed an evolutionary divergence in the function of glycosomes (modified peroxisomes) in diplonemids versus kinetoplastids. Our subcellular proteome provides a resource for future investigations into the unique cell biology of diplonemids.

Peroxisomes↗
PubMed1979

[Periodic, metabolic and structural phenomena in a protist, Euglena gracilis].

Sychronous divisions of Euglena gracilis strain Z can be obtained by various methods. When the cells are cultivated in a medium containing lactate as the sole carbon source, synchronous divisions are observed, independent of the conditions of illumination. Nevertheless, there exists a relationship between the phase of cell division and ther periods of light and darkness applied to the culture. During the cell cycle, the synthesis of macromolecules is discontinuous--this is true of nuclear and mitochondrial DNA, ribosomal and nonribosomal RNA, and certain proteins (cytochrome c 558). Cyclic variations in the structure of mitochondria and chloroplasts are observed. In the course of the cell cycle, sequential metabolic processes accompany structural modifications of the organelles. Also, at the beginning of the cycle, at the start of phase G1, the cytoplasmic ribosomes are synthesized, and then, in green euglenids, nonribosomal RNAs are formed. These syntheses of RNA precede enlargement of the chondriome and plastids. In mid-G1 phase, a new synthesis of RNA begins, which precedes synthesis of nuclear and mitochondrial DNA. At the end of G1 phase, division of organelles starts, beginning with the chondriome and plastids, arranged in a network.

Animals↗
PubMed2025

Native edaphoclimatic regions shape soil communities of crop wild progenitors.

Unveiling the soil biological communities ecologically associated with crop wild progenitors (CWPs) in their habitats of origin is essential for advancing productive and sustainable agriculture. A field survey was conducted to investigate the edaphoclimatic conditions and soil bacterial, fungal, protist, and invertebrate communities of 125 populations of direct progenitors of major crops for world agriculture. The wild populations clustered into four ecoregions shaped by two edaphoclimatic dimensions: one summarizing variations in soil sand contents and nutrients concentrations, and the other featuring changes in aridity, soil pH, and carbon storage potential. We identified a common soil core community across CWPs that varied significantly along deserts to tropical seasonal forests and savannas. The assembly of the soil core community was driven by varying environmental preferences amongst soil biodiversity kingdoms, reflecting potential shifts in their functional profiles. The tropical ecoregion exhibited higher proportion of acidophilic bacteria, fungal, and protist parasites, whilst desert ecosystems harboured greater abundances of saprophytic fungi and heterotrophic protists. Moreover, CWPs displayed unique microhabitats that incorporate variability into the soil community assembly. Our work reveals the biogeography of soil communities associated with CWPs, the first step towards the development of microbial rewilding initiatives.

centres of origin↗
PubMed1979

Possible evolutionary significance of spirochaetes.

Large symbiotic spirochaetes of the family Pillotaceae (e.g. pillotinas) are found in dry wood and subterranean termites (Hollande & Garagozlou 1967). These morphologically distinctive spirochaetes comprise several genera. Some of them contain microtubules within their protoplasmic cylinders. They demonstrate a variety of relations with their termite and protist hosts. Some are free-living within the lumen of the intestine, some tend to be associated with filamentous and other bacteria, some are found regularly coursing between the numerous undulipodia ( = eukaryotic flagella, cilia, and other (9 + 2) organelles of motility) of hypermastigotes and polymastigotes. Still other smaller termite spirochaetes are regularly attached to protists via specialized attachment sites. Some even form motility symbiosis with their host protists. The analogy between the behaviour of host-associated spirochaetes and the possible steps in the origin of the undulipodia and mitotic system of eukaryotes is discussed briefly.

Biological Evolution↗
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↗
PubMedDate not supplied

Relationships between specialized cells, capillaries and intermediary cytofibrillary elements. Xth Note. Biological evolution of the emonctory subsystem and stereotype in invertebrates.

The paper points out the importance of homeostasis as the most general system of the organism (Ist order system) and the 2nd order subsystem which composes it, discussing the relations between them and the biological evolution of the emonctory subsystem in protists and invertebrates. The emonctory structures, functions and stereotype and their component parts are studied in protists, spongia, coelenterata and coelomata: lower worms, annelids, their hyponeurian descendents (arthropods, molluses) and epineurian descedents echinoderms and protochordates (Stomochordata, Tunicata, Cephalochordata). The structure, functions and stereotypes of protonephridia and metanephridia and of substitutive (vicarious) emonctory organs (nephrocytes and peritoneal cells) are studied in coelomatic invertebrates. Their evolution appears to be directioned to localize within the limits of the emonctory subsystem. During their evolution, some nephridial functions are performed by the vicarious emonctory organs. The evolution of the subsystem in invertebrates appears to be based on stable characters and their relationships with variable features.

Animals↗
PubMed2015

Sex is a ubiquitous, ancient, and inherent attribute of eukaryotic life.

Sexual reproduction and clonality in eukaryotes are mostly seen as exclusive, the latter being rather exceptional. This view might be biased by focusing almost exclusively on metazoans. We analyze and discuss reproduction in the context of extant eukaryotic diversity, paying special attention to protists. We present results of phylogenetically extended searches for homologs of two proteins functioning in cell and nuclear fusion, respectively (HAP2 and GEX1), providing indirect evidence for these processes in several eukaryotic lineages where sex has not been observed yet. We argue that (i) the debate on the relative significance of sex and clonality in eukaryotes is confounded by not appropriately distinguishing multicellular and unicellular organisms; (ii) eukaryotic sex is extremely widespread and already present in the last eukaryotic common ancestor; and (iii) the general mode of existence of eukaryotes is best described by clonally propagating cell lines with episodic sex triggered by external or internal clues. However, important questions concern the relative longevity of true clonal species (i.e., species not able to return to sexual procreation anymore). Long-lived clonal species seem strikingly rare. We analyze their properties in the light of meiotic sex development from existing prokaryotic repair mechanisms. Based on these considerations, we speculate that eukaryotic sex likely developed as a cellular survival strategy, possibly in the context of internal reactive oxygen species stress generated by a (proto) mitochondrion. Thus, in the context of the symbiogenic model of eukaryotic origin, sex might directly result from the very evolutionary mode by which eukaryotic cells arose.

Cell Fusion↗
PubMed2026

Exploration of the antibacterial function of the Eutherian LEG1s.

Liver-enriched gene 1 (LEG1) encodes a novel protein family whose functions are not fully explored. LEG1 was first reported and characterized in zebrafish, where it encodes secreted proteins involved in liver development. In contrast, mammalian LEG1s exhibit a different expression pattern. The platypus monotreme lactation protein (platMLP) was uncovered in milk with antibacterial function. Studies in mouse and pig have shown that LEG1s are specifically expressed in the salivary glands; however, their function remains unclear. Evolutionarily, LEG1s are present in vertebrates and form three major clades, LEG1a, LEG1b, and LEG1c. Only a few invertebrates, protists, and bacteria retain LEG1 homologs, making the evolutionary origin of LEG1 obscure. In the current study, we conducted a thorough exploration of prokaryotic reference genomes and found that LEG1 predominantly exists in Actinomycetota. Given that Actinomycetota are well known for producing antibacterial compounds, and that platMLP can inhibit the growth of certain bacteria, we hypothesized that LEG1 is a conserved antibacterial protein. Recombinant LEG1s from each of the three clades were then purified and subjected to antibacterial tests, which showed that pig LEG1c and platMLP have divergent antibacterial activities. These findings support the hypothesis that the antibacterial function of LEG1 is conserved in eutherians but has undergone functional diversification following gene duplication events.

Animals↗
PubMed2025

Evolution of Transcription Factor-containing Superfamilies in Eukaryotes.

Regulation of gene expression helps determine various phenotypes in most cellular life forms. It is orchestrated at different levels and at the point of transcription initiation by transcription factors (TFs). TFs bind to DNA through domains that are evolutionarily related, by shared membership of the same superfamilies (TF-SFs), to those found in other nucleic acid binding and protein-binding functions (nTFs for non-TFs). Here we ask how TF DNA binding sequence families in eukaryotes have evolved in relation to their nTF relatives. TF numbers scale by power law with the total number of protein-coding genes differently in different clades, with fungi usually showing sub-linear powers whereas chordates show super-linear scaling. The LECA probably encoded a complex regulatory machinery with both TFs and nTFs, but with an excess of nTFs when compared to the relative distribution of TFs and nTFs in extant organisms. Losses drive the evolution of TFs and nTFs, with the possible exception of TFs in animals for some tree topologies. TFs are highly dynamic in evolution, showing higher gain and loss rates than nTFs in some TF-SFs though both are conserved to similar extents. Gains of TFs and nTFs are driven by the appearance of a large number of new sequence clusters in a small number of nodes, which determine the presence of as many as a third of extant TFs and nTFs as well as the relative presence of TFs and nTFs. Whereas nodes showing explosion of TF numbers belong to multicellular clades, those for nTFs lie among the fungi and the protists.

Transcription Factors↗
PubMed2026

First identification and molecular subtyping of Blastocystis spp. in donkeys in Aksaray province, Türkiye.

Blastocystis is a common intestinal protist worldwide that can infect humans and animals. Although its molecular epidemiology in Türkiye is mostly focused primarily on humans and livestock, equids have received limited attention despite their traditional roles and frequent contact with humans and other animals in rural environments. This study aimed to determine the molecular prevalence and subtype (ST) distribution of Blastocystis spp. in donkeys in Aksaray Province, providing the first molecular data on donkeys in Türkiye. A total of 182 fresh fecal samples were collected from donkeys in nine villages within Aksaray province. Genomic DNA was extracted, and the small subunit ribosomal RNA (SSU rRNA) gene fragment of Blastocystis spp. was amplified via PCR analysis. Positive isolates were sequenced bidirectionally for identification and subsequent phylogenetic analysis of Blastocystis in donkeys. The overall molecular prevalence of Blastocystis spp. in donkeys was 4.4% (8/182). The infection rate was higher in young donkeys (under 3 years old; 8.33%) than in adults (3 years or older; 2.46%). However, this difference was not statistically significant. Sequence analysis of the positive PCR products revealed the presence of one known livestock-specific subtype, ST10. Phylogenetic analysis showed that the ST10 isolates characterized in this study clustered with isolates identified from different hosts. This study provides the first molecular data on Blastocystis presence in donkeys in Türkiye. The exclusive detection of ST10 suggests potential cross-species transmission, likely facilitated by the traditional practice of co-housing donkeys with other animals in confined barns. These findings indicate that donkeys may contribute to Blastocystis transmission, underscoring the importance of a "One Health" approach in future epidemiological surveillance.

Animals↗
PubMed2026

Infection cycles of viruses of the phylum Nucleocytoviricota.

The phylum Nucleocytoviricota, formerly known as nucleocytoplasmic large DNA viruses (NCLDVs), comprises evolutionarily related viruses with remarkably diverse genome sizes, coding capacities and virion morphologies. These viruses infect hosts across the eukaryotic tree of life, from protists to humans, and are believed to have emerged during the early stages of eukaryotic evolution. How the basic aspects of virus-host interaction have evolved in different lineages and whether they share a conserved infection cycle remain unclear. In this Review, we synthesize the information on the infection cycles of model representatives from the major orders within the phylum, revealing both shared traits and lineage-specific innovations. We compare the information available for the extensively studied poxviruses, asfiviruses, iridoviruses and chloroviruses with insights from the rapidly expanding literature on the mimiviruses, pandoraviruses, marseilleviruses and pithoviruses. We provide an overview of the molecular details underlying the key stages of Nucleocytoviricota infection cycles: entry via membrane fusion, formation of viral factories organized via phase separation, genome replication, virion morphogenesis through a crescent intermediate, and egress. We highlight outstanding questions in the field, unify concepts across traditionally separated research areas, and provide a conceptual framework to guide future cell biology studies on large double-stranded DNA viruses.

DNA Viruses↗
PubMed2025

Inactivation of β-1,3-glucan synthase-like 5 confers broad-spectrum resistance to Plasmodiophora brassicae pathotypes in cruciferous plants.

Clubroot disease, caused by the obligate intracellular rhizarian protist Plasmodiophora brassicae, is devastating to cruciferous crops worldwide. Widespread field P. brassicae pathotypes frequently overcome the pathotype-specific resistance of modern varieties, posing a challenge for durable control of this disease. Here a genome-wide association study of 3 years of data comprising field clubroot phenotyping of 244 genome-resequenced Brassica napus accessions identified a strong association of β-1,3-glucan synthase-like 5 (GSL5) with clubroot susceptibility. GSL5 was evolutionarily conserved, and inactivation of GSL5 by genome editing in Arabidopsis, B. napus, Brassica rapa and Brassica oleracea conferred broad-spectrum, high-level resistance to P. brassicae pathotypes without yield penalties in B. napus. GSL5 inactivation derepressed the jasmonic acid-mediated immunity during P. brassicae secondary infection, and this immune repression was possibly reinforced through stabilization of GSL5 by a P. brassicae effector, facilitating clubroot susceptibility. Our study provides durable resistance resources for cruciferous clubroot disease control and insights into plant resistance against intracellular eukaryotic phytopathogens.

Disease Resistance↗
PubMed2026

A compendium of horizontal gene transfers in Metazoa.

With more eukaryotic genomes available for study researchers have been able to identify a growing number of horizontal gene transfer (HGT) candidates. We compiled 9,495 protein coding genes that were identified as horizontally transferred to metazoan hosts in the published literature. This dataset contains gene transfers from bacteria, fungi, archaea and protists to metazoans. We assigned a confidence score to each gene based on the methods used in the scientific paper reporting HGT. All the coding sequences and protein sequences for the HGT genes are stored in a fig share repository. This dataset can be used to identify trends in genome and protein evolution and provide a foundation for creating a centralized HGT database for eukaryotes.

Gene Transfer, Horizontal↗
PubMed2026

CoMR: an integrative scoring pipeline for comprehensive mitochondrial proteome reconstruction across eukaryotes.

Mitochondrial proteome reconstruction from eukaryotic sequence data typically relies on prediction of mitochondrial targeting signals (MTSs). However, MTS predictors are primarily trained on model organisms and may perform poorly in phylogenetically divergent lineages or in organisms with atypical or reduced targeting sequences. Accurate reconstruction therefore requires integration of complementary sources of evidence beyond targeting prediction alone. We developed Comprehensive Mitochondrial Reconstructor (CoMR), an integrative workflow that combines targeting prediction, curated homology searches, large-scale similarity searches, and automated phylogenetic analysis within a unified scoring framework. Benchmarking on the model yeast Saccharomyces cerevisiae yielded strong discriminatory performance [receiver operating characteristic (ROC)-area under the curve (AUC) = 0.92], exceeding standalone prediction with TargetP2, a predictor of N-terminal targeting peptides (ROC-AUC = 0.72). In the divergent anaerobic protist Paratrimastix pyriformis, CoMR maintained robust performance (ROC-AUC = 0.86) validated with an experimental proteome despite extreme class imbalance, achieving a precision-recall AUC of 0.183 (~78-fold enrichment over random expectation and ~10-fold improvement over TargetP2). Ablation analyses demonstrate that predictive performance is robust to individual evidence-layer removal, while overlap analyses showed that homology-based searches recovered candidates missed by targeting predictors, particularly in P. pyriformis. Overall, CoMR improves mitochondrial proteome reconstruction over targeting prediction alone and provides a reproducible workflow for predicting mitochondrial and mitochondrion-related organelle protein repertoires across eukaryotes to aid investigations of organelle evolution and proteome reduction.

Proteome↗
PubMed2026

Long-read transcriptomics corrects Trichomonas vaginalis intron annotations and refines transcript-end features.

BACKGROUND: Trichomonas vaginalis causes the most prevalent non-viral sexually transmitted infection worldwide. Despite its large genome (181.5 Mb; 36,310 predicted protein-coding genes in NYU_TvagG3_2), intron annotations remain limited and inconsistently validated. A recent short-read RNA-seq study reported 63 putative active introns, but short reads can misassign splice boundaries and cannot resolve complete transcript structures. METHODS: We integrated Oxford Nanopore direct RNA sequencing (DRS), ONT cDNA long-read sequencing, and Illumina RNA-seq to refine intron annotations, transcript-end features, and UTR boundaries in T. vaginalis. Candidate introns were validated by targeted PCR and Sanger sequencing, and representative splicing events were further assessed using public SRA datasets. RESULTS: Starting from 31 historically annotated introns, motif-guided long-read screening and orthogonal validation identified 17 additional validated introns, increasing the curated set to 48 confirmed introns. Among these 17 events, three were previously unrecognized in the current NYU_TvagG3_2 reference annotation. We also corrected five reported loci, including two false-positive introns, two splice-coordinate misannotations, and one gene-sequence error. DRS further supported transcript termination site mapping, UAAA polyadenylation-signal profiling relative to poly(A) addition sites, and single-molecule poly(A)-tail estimation. StringTie mixed-mode assemblies provided updated UTR boundaries for intron-bearing transcripts and transcripts without curated introns. CONCLUSIONS: This study provides a rigorously validated, long-read-refined resource of intron annotations, UTR boundaries, and UAAA-guided transcript-end features for T. vaginalis, together with a reproducible workflow for non-model protists. These refinements improve the current reference annotation and support future studies of functional genomics, parasite biology, pathogenesis, and diagnostic development.

Trichomonas vaginalis↗
PubMed2022

CMTr mediated 2'-O-ribose methylation status of cap-adjacent nucleotides across animals.

Cap methyltransferases (CMTrs) O methylate the 2' position of the ribose (cOMe) of cap-adjacent nucleotides of animal, protist, and viral mRNAs. Animals generally have two CMTrs, whereas trypanosomes have three, and many viruses encode one in their genome. In the splice leader of mRNAs in trypanosomes, the first four nucleotides contain cOMe, but little is known about the status of cOMe in animals. Here, we show that cOMe is prominently present on the first two cap-adjacent nucleotides with species- and tissue-specific variations in Caenorhabditis elegans, honeybees, zebrafish, mouse, and human cell lines. In contrast, Drosophila contains cOMe primarily on the first cap-adjacent nucleotide. De novo RoseTTA modeling of CMTrs reveals close similarities of the overall structure and near identity for the catalytic tetrad, and for cap and cofactor binding for human, Drosophila and C. elegans CMTrs. Although viral CMTrs maintain the overall structure and catalytic tetrad, they have diverged in cap and cofactor binding. Consistent with the structural similarity, both CMTrs from Drosophila and humans methylate the first cap-adjacent nucleotide of an AGU consensus start. Because the second nucleotide is also methylated upon heat stress in Drosophila, these findings argue for regulated cOMe important for gene expression regulation.

Animals↗