Microbial predators form a new supergroup of eukaryotes.

Molecular phylogenetics of microbial eukaryotes has reshaped the tree of life by establishing broad taxonomic divisions, termed supergroups, that supersede the traditional kingdoms of animals, fungi and plants, and encompass a much greater breadth of eukaryotic diversity1. The vast majority of newly discovered species fall into a small number of known supergroups. Recently, however, a handful of species with no clear relationship to other supergroups have been described2-4, raising questions about the nature and degree of undiscovered diversity, and exposing the limitations of strictly molecular-based exploration. Here we report ten previously undescribed strains of microbial predators isolated through culture that collectively form a diverse new supergroup of eukaryotes, termed Provora. The Provora supergroup is genetically, morphologically and behaviourally distinct from other eukaryotes, and comprises two divergent clades of predators-Nebulidia and Nibbleridia-that are superficially similar to each other, but differ fundamentally in ultrastructure, behaviour and gene content. These predators are globally distributed in marine and freshwater environments, but are numerically rare and have consequently been overlooked by molecular-diversity surveys. In the age of high-throughput analyses, investigation of eukaryotic diversity through culture remains indispensable for the discovery of rare but ecologically and evolutionarily important eukaryotes.

The Morphology, Ultrastructure and Molecular Phylogeny of a New Soil-Dwelling Kinetoplastid Avlakibodo gracilis gen. et sp. nov. (Neobodonida; Kinetoplastea).

Kinetoplastids represent a stockpile of undiscovered protist diversity. Free-living members of this group have been studied less intensively compared to their important parasitic relatives. We have isolated a new soil-dwelling bacteriotrophic kinetoplastid, which is described here as a new genus and new species, Avlakibodo gracilis gen. et sp. nov. Phylogenetic analysis of 18S rRNA genes showed highly supported sister relationship of this protist with the clade uniting Neobodo borokensis, Neobodo curvifilus, Neobodo saliens, Actuariola framvarensis, some Neobodo designis isolates and several environmental sequences, with high statistical support. We have reconstructed the organization of the microtubular cytoskeleton of A. gracilis and determined the origins of the main bands of microtubules. Characteristic ultrastructural features include cytostome associated microtubules (FAS), cytopharynx associated additional microtubules (CMT), microtubular prism (nemadesm) and three microtubular roots (R1, R2 and R3).

On the origin of TSAR: morphology, diversity and phylogeny of Telonemia.

Telonemia is a poorly known major phylum of flagellated eukaryotes with a unique combination of morphological traits. Phylogenomics recently revealed the phylogenetic position of telonemids as sister to SAR, one of the largest groups of eukaryotes, comprising Stramenopiles, Alveolata and Rhizaria. Due to this key evolutionary position, investigations of telonemids are of critical importance for elucidating the origin and diversification of an astounding diversity of eukaryotic forms and life strategies. To date, however, only two species have been morphologically characterized from Telonemia, which do not represent this genetically very diverse group. In this study, we established cultures for six new telonemid strains, including the description of five new species and a new genus. We used these cultures to update the phylogeny of Telonemia and provide a detailed morphological and ultrastructural investigation. Our data elucidate the origin of TSAR from flagellates with complex morphology and reconstruction of the ancestral structure of stramenopiles, alveolates and rhizarians, and their main synapomorphic characters. Since telonemids are a common component of aquatic environments, the features of their feeding, behaviour and ecological preferences observed in clonal cultures and the results of global metabarcoding analysis contribute to a deeper understanding of organization of microbial food webs.