Neobodonids are dominant kinetoplastids in the global ocean

Abstract

Kinetoplastid flagellates comprise basal mostly free-living bodonids and derived obligatory parasitic trypanosomatids, which belong to the best-studied protists. Due to their omnipresence in aquatic environments and soil, the bodonids are of ecological significance. Here, we present the first global survey of marine kinetoplastids and compare it with the strikingly different patterns of abundance and diversity in their sister clade, the diplonemids. Based on analysis of 18S rDNA V9 ribotypes obtained from 124 sites sampled during the Tara Oceans expedition, our results show generally low to moderate abundance and diversity of planktonic kinetoplastids. Although we have identified all major kinetoplastid lineages, 98% of kinetoplastid reads are represented by neobodonids, namely specimens of the Neobodo and Rhynchomonas genera, which make up 59% and 18% of all reads, respectively. Most kinetoplastids have small cell size (0.8-5 µm) and tend to be more abundant in the mesopelagic as compared to the euphotic zone. Some of the most abundant operational taxonomic units have distinct geographical distributions, and three novel putatively parasitic neobodonids were identified, along with their potential hosts.

A metagenomic assessment of microbial eukaryotic diversity in the global ocean

“…The fact that some taxonomic groups that are typically larger (e.g., Radiolaria) were found in the picoeukaryotic fraction could be explained by the presence of smaller life cycle stages or to filtration artifacts (Massana et al, 2015). Apart from Prymnesiophyceae and Diplonemea, we could retrieve a relatively important signal of Kinetoplastida in the picoeukaryotic fraction by means of metagenomics (median relative abundance 0.5%), a similar abundance already seen in Tara Oceans V9 amplicons but not detected in the metagenomes from that same data set (Flegontova et al, 2018).…”

OUP accepted manuscript

“…In our Kinetoplastea tree, Parabodonida are strongly supported (95% bootstrap support), Trypanosomatida moderately supported (79%), Eubodonida poorly supported (30%), and Neobodonida (1182 sequences) is not monophyletic, but instead represented by a paraphyletic cluster of clades at the base of Metakinetoplastina. Some of these clades (especially Dimastigella spp., Neobodo spp., Rhynchomonas spp., and the clade MET7) seem to be important in marine environments ( 50 ). Taking into account the topology of our tree and previous publications ( 14 , 46 , 49 , 51–56 ), we cannot rule out the possibility that Neobodonida are paraphyletic, and we decided to omit the term Neobodonida from our classification and classify their sequences as Metakinetoplastina.…”

“…A majority of described Metamonada and Discoba species are characterized exclusively by morphological features with no molecular data available; consequently, we have a limited ability to assign species labels to the molecular diversity of Excavata in environmental samples. On the other hand, careful analyses of molecular data from environmental studies based on our database should help significantly to reveal the true diversity of existing excavate groups: for instance, analyses using our database revealed novel diversity within Diplonemea and Kinetoplastea ( 17 , 50 ).…”

The Functional Characterization of TcMyoF Implicates a Family of Cytostome-Cytopharynx Targeted Myosins as Integral to the Endocytic Machinery of Trypanosoma cruzi

“…Notably, T. cruzi employs a more ancient mode of endocytosis analogous to what is observed in its monoxenous trypanosomatid relatives (e.g., Paratrypanosoma confusum) or even in free-living bacterivorous kinetoplastids (bodonids) (12). These organisms, like many ciliates, feed via a tubular invagination (cytopharynx) that originates at a cytoplasmic membrane opening (cytostome) and, at least for free-living protozoans, is used to filter feed and engulf prey (13,14). In T. cruzi, endocytosed material is initially shuttled to late endosome-like storage structures known as reservosomes that, when needed, are converted into digestive lysosomes for the liberation of simple nutrients.…”