Climate change is altering microbial ecosystems at a global scale, yet the role of free-living amoebae within these shifting microbiomes remains incompletely understood. Free-living amoebae occupy soil, water, air, and built environments, where they contribute to microbial diversity, regulate nutrient cycling, and host diverse bacterial, fungal, and viral microorganisms. As temperature, moisture, and land-use patterns change, amoebal behaviour and their associated microbiomes may shift in ways that may affect soil fertility, water quality, microbial network stability, and the persistence of opportunistic pathogens. Through grazing, amoebae regulate bacterial turnover and mineral nutrient release from microbial biomass, providing a mechanistic link between nutrient cycling and plant accessible nutrient pools that underpin soil fertility. Understanding these dynamics is essential for planetary microbiome research and for strengthening One Health approaches that link environmental, animal, and human health. Herein, we discuss free-living amoebae in the context of climate change, the planetary microbiome, and One Health, and consider how their ecological roles may relate to broader shifts in microbial systems. We synthesise current evidence linking free-living amoebae to climate-responsive microbiome dynamics and propose their inclusion within planetary microbiome and One Health frameworks as responsive ecological indicators. Integrating amoebae into surveillance, ecological modelling, and climate-adaptation strategies may improve predictive capacity for tracking climate-driven microbial change.
An international group of 49 scientists from 12 countries assembled at Brock University, St. Catharines, Ontario, Canada, from June 22–27, 2025, for the 11th International Symposium on Testate Amoebae (ISTA-11 Niagara). The meeting, jointly organized by the International Society of Testate Amoebae Research (ISTAR) and the Canadian Association of Palynologists (CAP), marked a significant milestone as the first ISTA meeting held in North America. Participation included 19 students, underscoring strong engagement from early-career researchers. The largest national delegation was from Canada (17 participants), followed by China, Switzerland, and the United States (six participants each). The scientific program comprised 41 oral and 12 poster presentations, reflecting the continued growth and diversification of research on testate amoebae.
Trachelopyllidae Kent, 1881 is a family of predatory litostomatean ciliates distinguished by a three-rowed dorsal brush composed of two dikinetidal rows and one monokinetid row, and one or more types of organic epicortical scales called lepidosomes. To date, the taxonomy of the nine genera comprising the family has been based, almost exclusively, on the types of scales and their combinations together with cell morphometry. Six of the nine genera are monotypic. To date, molecular data has been available from only four species representing two genera. With the aim of broadening the molecular characterization of the Trachelophyllidae, we present new rRNA cistron sequences of three trachelophyllid species from Idaho, USA, identified by scanning electron microscopy and representing three genera of the family not yet sequenced, and we describe a novel species representing a new genus from the Czech Republic. The results confirm the extraordinarily conserved nature of the 18S rRNA gene and ITS2 regions in the Trachelophyllidae and demonstrate the discordance between lepidosome-based taxonomy and the rRNA cistron-based molecular phylogeny in this group. Additionally, we consider ciliary ultrastructural features unique to members of the Trachelophyllidae and Lingulotrichidae (suborder Trachelophyllina Grain, 1994).
Dictyostelia are aggregative multicellular (AGM) amoebae, whose life cycle alternates between solitary feeding and multicellular fruiting. This is by far the oldest and most diverse AGM lineage with an evolutionary depth equal to Vertebrata. The best-known species is the model organism, Dictyostelium discoideum. However, many traits studied in Dic. discoideum differ among the 170+ species, so a robust and comprehensive phylogeny is required to understand trait evolution. We constructed a dictyostelid-wide phylogeny with 173 deduced protein sequences using published data and 13 new proteomes. Phylogenetic analysis of the data with an Amoebozoan outgroup confidently places four poorly studied “orphan” taxa among its deepest branches. Thus, Synstelium polycarpum and Rostrostelium ellipticum appear as the deepest branches in Acytosteliaceae, supporting parallel evolution of the undifferentiated “acytostelid-like” morphology. Speleostelium caveatum, the only known cannibalistic species, is confirmed as the deepest branch in Raperosteliaceae, and Coremiostelium polycephalum is sister to both Dictyosteliaceae and Raperosteliaceae. The latter observation requires erecting a new family, which we designate Coremiosteliaceae. We also erect genus Porphyrostelium to accommodate the molecularly highly distinct and diverse collection of isolates previously grouped together as Dictyostelium purpureum.
