Journal of Eukaryotic Microbiology最新文献

Benthic foraminifera are characterized by their rapid response and high resistance to variable and extreme conditions such as those typically found in intertidal environments. However, knowledge of cellular and metabolic adaptations by foraminifera remains incomplete. Here we explore the metabolic profile of three species from an intertidal mudflat: Haynesina germanica (kleptoplast, mixotrophic), Elphidium oceanense, and Ammonia confertitesta (heterotrophic). Given the challenges associated with culturing foraminifera, specimens were collected directly from the field. To analyze their metabolic profiles, a non-targeted gas chromatography–mass spectrometry methodology was optimized with the aim of reducing sample size. We constructed a foraminifera-specific library containing 382 features. Within the 30 metabolites identified, those present in all three species include osmolytes, oxidant- and thermo-protective molecules, which are consistent with their high tolerance to variations in environmental conditions. Species-specific features were also observed. A. confertitesta accumulates myoinositol, aspartate, and asparagine. H. germanica accumulated malate, glycerate, and glycolate/glyoxylate, indicating concurrent activity of a C4-like carbon concentrating mechanism and photorespiratory metabolism. Our approach enabled us to discriminate between the species based on their metabolites and highlights two probable metabolic pathways not previously described in kleptoplast foraminifera. These metabolic adaptations likely contribute to the ecological success of intertidal foraminiferal species.

Copepods, dominant marine zooplankton, are hosts to microbial eukaryotic symbionts, but the copepod eukaryome remains largely unexplored. We used 18S rRNA gene primers with reduced metazoan amplification to identify microbial eukaryotes in a culture of Calanus finmarchicus (Copepoda). Samples were taken from the inlet water (99.5% of reads from non-copepod sources) and the contents of the culture, which included ambient water (99.7%), bulk (many crushed copepods, 60.2%), individual copepods (1%–41%, mean = 7.4), and bulk fecal pellets (74%). The microbial eukaryotic community in the culture differed from the inlet water. The culture contained saprotrophs and bacterivores typical of eutrophic aquacultures and known parasites of copepods. Individual copepod eukaryomes varied in richness (8–33 operational taxonomic units, mean = 16.1) and revealed variation in non-copepod read yields related to specific taxa. Perkinsea, not previously reported in copepods, as well as Ascomycota and Basidiomycota (Fungi), formed the core eukaryome (found in > 90% of individuals), indicating potentially important symbiosis. The small eukaryome, relative to reported microbiomes in C. finmarchicus, suggests that ecological inferences from microbiomes, which largely address bacteria, are not readily applicable to the eukaryotic microbes. The study underpins the need for investigations of eukaryomes.

Telonemia is a fascinating and understudied group of microbial eukaryotes known to have a vast diversity that is still uncharacterized. In fact, although their phylogenetic position is still actively debated, their diversity and biology are largely unexplored: to date, there are only seven described species in three genera, although there are estimated to be hundreds more unknown lineages. Here, we describe the isolation and characterization of two new strains, including a new genus (Hyaliora molinica n. gen. n. sp.) and a new species (Telonema blandense n. sp.), and the re-isolation of a previously characterized telonemid, Telonema subtile, accompanied by new behavioral observations. We present morphological measurements highlighting differences among the isolates and a phylogenetic tree incorporating their 18S rRNA gene sequences. Furthermore, key aspects of their cell biology and structure are highlighted to provide insights into the evolution of their potential sister groups. Since they are relevant not only phylogenetically but also play a crucial role in food webs with some abundant representatives in aquatic ecosystems, the findings of this study provide further sampling and culturing of Telonemia to increase the knowledge of the hidden diversity and evolution of this mysterious group.

As the ecological and evolutionary importance of symbiotic interactions between protists (microbial eukaryotes) and prokaryotes (bacteria and archaea) is better appreciated, keeping an overview of their diversity and the literature becomes a growing and ongoing challenge. Here I present the Protist-Prokaryote Symbiosis Database (PPSDB), comprising 1146 manually curated interaction statements sourced from 443 publications, where biological taxonomy, anatomical localization, and analytical methods applied have been annotated and mapped to external databases and ontologies, such as Wikidata, NCBI Taxonomy, and Gene Ontology. I describe how its data model deals practically with challenges such as incomplete information and inconsistent taxon concepts, which will be applicable to similar projects. Both the model and underlying Wikibase software platform are highly extensible, so new items and properties can easily be added. Unlike a static table or list of citations, PPSDB is a structured knowledge base that enables programmatic access and powerful, integrated semantic queries. The database is available at https://ppsdb.wikibase.cloud/.

While oxygen is essential for metabolic processes, many ciliate species thrive in low-oxygen or even oxygen-free environments. Anaerobic ciliates have adapted to a broad range of such habitats, yet have long remained understudied compared to their aerobic counterparts. In recent years, however, interest in these lineages has grown, including in the family Tropidoatractidae Rotterová et al. 2018 (Order Metopida), which currently comprises of two genera, Tropidoatractus Levander, 1894 and Palmarella Jankowski, 1975, and five described species. This report presents two novel freshwater species of Tropidoatractidae, identified through a combination of morphological analysis and 18S rRNA gene phylogeny. Tropidoatractus songi n. sp. is identified by its arcuate body and 11–13 oblique rows of cortical granules between ciliary rows. Tropidoatractus rostrum n. sp. possesses an elongated, ellipsoidal body; a prominent, dark, beak-like anterior end to the preoral dome brim; a macronucleus that is closely associated with rod-shaped endosymbiotic prokaryotes; and sparse, irregular cortical granules. Both species exhibit a diplostichomonad paroral membrane. Phylogenetic analyses of the 18S rRNA gene confirm their affiliation with Tropidoatractus, revealing previously unrecognized species diversity among anaerobic freshwater ciliates.