Endosymbiont Capture, a Repeated Process of Endosymbiont Transfer with Replacement in Trypanosomatids Angomonas spp

Characterization of Allobodo yubaba sp. nov. and Novijibodo darinka gen. et sp. nov., cultivable free-living species of the phylogenetically enigmatic kinetoplastid taxon Allobodonidae

Kinetoplastids are a large and diverse protist group, spanning ecologically important free-living forms to medically important parasites. The taxon Allobodonidae holds an unresolved position within kinetoplastids, and the sole described species, Allobodo chlorophagus, is uncultivated, being a necrotroph/parasite of macroalgae. Here we describe Allobodo yubaba sp. nov. and Novijibodo darinka gen. nov. et sp. nov., both free-living bacterivores isolated into monoeukaryotic cultures. Electron microscopy shows that both A. yubaba and N. darinka have a microtubular prism in the feeding apparatus (absent in A. chlorophagus), and an ovoid eukinetoplast, rather than pan-kDNA as in A. chlorophagus. Phylogenetic analyses of SSU rDNA sequences robustly place A. yubaba as the sister to A. chlorophagus, while N. darinka branches separately within Allobodonidae, as a sister group of undescribed freshwater isolates. We view Allobodonidae as containing at least four genus-level clades: Allobodo (A. chlorophagus and A. yubaba n. sp.), an undescribed fresh-water clade, an undescribed marine clade, and now Novijibodo-with N. darinka as its sole known member. Electron microscopy also revealed a rod-shaped gram-negative bacterial cytoplasmic endosymbiont in our N. darinka isolate. The availability of these species in monoeukaryotic culture should facilitate future research, including resolving the position of Allobodonidae using phylogenomic approaches.

Phylogenetic and structural characterization of Kentomonas inusitatus n. sp.: Unique insect trypanosomatid of the Strigomonadinae subfamily naturally lacking bacterial endosymbiont

All insect trypanosomatids of the subfamily Strigomonadinae harbor a proteobacterial symbiont in their cytoplasm and unique ultrastructural cell organization. Here, we report an unexpected finding within the Strigomonadinae subfamily: the identification of a new species lacking bacterial symbiont, represented by two isolates obtained from Calliphoridae flies in Brazil and Uganda. This species is hereby designated as Kentomonas inusitatus n. sp. Molecular investigations targeting symbiont DNA, cell proliferation, and ultrastructural analyses agreed with the absence of bacterial symbionts in cultured flagellates. PCR-screening specifically targeting symbiont DNA corroborated the absence of symbionts in K. inusitatus present in the intestine of the respective host flies. K. inusitatus exhibited forms varying in size and shape. While displaying overall ultrastructural features of the Strigomonadinae, the novel species showed mitochondrial branches juxtaposed to the plasma membrane in locations both without and notable, with subpellicular microtubules. The discovery of the first Strigomonadinae species naturally lacking a symbiont and closely related to K. sorsogonicus, suggests a unique evolutionary history for the genus Kentomonas. Our findings provide novel insights into the complex relationships between trypanosomatids and their symbionts.

Host-symbiont interactions in Angomonas deanei include the evolution of a host-derived dynamin ring around the endosymbiont division site

The trypanosomatid Angomonas deanei is a model to study endosymbiosis. Each cell contains a single β-proteobacterial endosymbiont that divides at a defined point in the host cell cycle and contributes essential metabolites to the host metabolism. Additionally, one endosymbiont gene, encoding an ornithine cyclodeaminase (OCD), was transferred by endosymbiotic gene transfer (EGT) to the nucleus. However, the molecular mechanisms mediating the intricate host/symbiont interactions are largely unexplored. Here, we used protein mass spectrometry to identify nucleus-encoded proteins that co-purify with the endosymbiont. Expression of fluorescent fusion constructs of these proteins in A. deanei confirmed seven host proteins to be recruited to specific sites within the endosymbiont. These endosymbiont-targeted proteins (ETPs) include two proteins annotated as dynamin-like protein and peptidoglycan hydrolase that form a ring-shaped structure around the endosymbiont division site that remarkably resembles organellar division machineries. The EGT-derived OCD was not among the ETPs, but instead localizes to the glycosome, likely enabling proline production in the glycosome. We hypothesize that recalibration of the metabolic capacity of the glycosomes that are closely associated with the endosymbiont helps to supply the endosymbiont with metabolites it is auxotrophic for and thus supports the integration of host and endosymbiont metabolic networks. Hence, scrutiny of endosymbiosis-induced protein re-localization patterns in A. deanei yielded profound insights into how an endosymbiotic relationship can stabilize and deepen over time far beyond the level of metabolite exchange.

Genomics of Trypanosomatidae: Where We Stand and What Needs to Be Done?

Trypanosomatids are easy to cultivate and they are (in many cases) amenable to genetic manipulation. Genome sequencing has become a standard tool routinely used in the study of these flagellates. In this review, we summarize the current state of the field and our vision of what needs to be done in order to achieve a more comprehensive picture of trypanosomatid evolution. This will also help to illuminate the lineage-specific proteins and pathways, which can be used as potential targets in treating diseases caused by these parasites.