The Bacterium Endosymbiont of Crithidia deanei Undergoes Coordinated Division with the Host Cell Nucleus

Abstract

In trypanosomatids, cell division involves morphological changes and requires coordinated replication and segregation of the nucleus, kinetoplast and flagellum. In endosymbiont-containing trypanosomatids, like Crithidia deanei, this process is more complex, as each daughter cell contains only a single symbiotic bacterium, indicating that the prokaryote must replicate synchronically with the host protozoan. In this study, we used light and electron microscopy combined with three-dimensional reconstruction approaches to observe the endosymbiont shape and division during C. deanei cell cycle. We found that the bacterium replicates before the basal body and kinetoplast segregations and that the nucleus is the last organelle to divide, before cytokinesis. In addition, the endosymbiont is usually found close to the host cell nucleus, presenting different shapes during the protozoan cell cycle. Considering that the endosymbiosis in trypanosomatids is a mutualistic relationship, which resembles organelle acquisition during evolution, these findings establish an excellent model for the understanding of mechanisms related with the establishment of organelles in eukaryotic cells.

Predicting the Proteins of Angomonas deanei, Strigomonas culicis and Their Respective Endosymbionts Reveals New Aspects of the Trypanosomatidae Family

“…Accordingly, δ and ε-tubulins are present in organisms that possess basal bodies and flagella [36]. γ-tubulin is localized in the basal body of A. deanei [14] as in other trypanosomatids [35]. Additionally, in common with other trypanosomatids, five centrins were identified in A. deanei and S. culicis .…”

“…The bacterium divides in coordination with the host cell structures, especially the nucleus, with each daughter cell carrying only one symbiont [14]. The presence of the prokaryote causes ultrastructural alterations in the host trypanosomatid, which exhibits a reduced paraflagellar structure and a typical kinetoplast DNA network [15], [16], [17].…”

Development of a toolbox to dissect host-endosymbiont interactions and protein trafficking in the trypanosomatid Angomonas deanei

“…Angomonas along with the genera Strigomonas and Kentomonas form a monophyletic clade within the Kinetoplastea, the subfamily Strigomonadinae that is characterized by the presence of a single β-proteobacterial endosymbiont in their cytoplasm [18]. The endosymbiont is enclosed by two membranes and a reduced peptidoglycan layer [19], divides synchronously with the host cell, and is vertically transmitted to progeny cells [20]. Whereas most trypanosomatids are nutritionally fastidious and have a strict requirement for heme and several amino acids, members of the Strigomonadinae can grow in defined media lacking heme and containing a reduced number of amino acids because many metabolites can be synthesized by the endosymbiont and delivered to the host [21–23].…”

A Draft Genome of the Honey Bee Trypanosomatid Parasite Crithidia mellificae

“…In addition to this unusual organelle, at least six trypanosomatid species are known to harbor betaproteobacterial endosymbionts, some of which can be cured in culture by the presence of antibiotics [27], [28]. Consistent with their role as endosymbionts, trypanosomatid descendants rendered endosymbiont-free exhibited altered nutritional requirements [27], [29], [30].…”