The stability of endosymbiotic associations between eukaryotes and bacteria depends on a reliable mechanism ensuring vertical inheritance of the latter. Here, we demonstrate that a host-encoded protein, located at the interface between the endoplasmic reticulum of the trypanosomatid Novymonas esmeraldas and its endosymbiotic bacterium Ca. Pandoraea novymonadis, regulates such a process. This protein, named TMP18e, is a product of duplication and neo-functionalization of the ubiquitous transmembrane protein 18 (TMEM18). Its expression level is increased at the proliferative stage of the host life cycle correlating with the confinement of bacteria to the nuclear vicinity. This is important for the proper segregation of bacteria into the daughter host cells as evidenced from the TMP18e ablation, which disrupts the nucleus-endosymbiont association and leads to greater variability of bacterial cell numbers, including an elevated proportion of aposymbiotic cells. Thus, we conclude that TMP18e is necessary for the reliable vertical inheritance of endosymbionts.

• Klíčová slova
• Leishmaniinae, Pandoraea, TMEM18, Trypanosomatidae, endosymbiosis,
• MeSH
• Bacteria MeSH
• Eukaryota MeSH
• symbióza fyziologie   MeSH
• Trypanosomatina * mikrobiologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Here we describe the new trypanosomatid, Phytomonas borealis sp. n., from the midgut of the spiked shieldbugs, Picromerus bidens (Linnaeus), collected in two locations, Novgorod and Pskov Oblasts of Russia. The phylogenetic analyses, based on the 18S rRNA gene, demonstrated that this flagellate is a sister species to the secondary monoxenous Phytomonas nordicus Frolov et Malysheva, 1993, which was concurrently documented in the same host species in Pskov Oblast. Unlike P. nordicus, which can complete its development (including exit to haemolymph and penetration into salivary glands) in Picromerus bidens, the new species did not form any extraintestinal stages in the host. It also did not produce endomastigotes, indispensable for transmission in other Phytomonas spp. These observations, along with the fact that P. bidens overwinters at the egg stage, led us to the conclusion that the examined infections with P. borealis were non-specific. Strikingly, the flagellates from the Novgorod population contained prokaryotic endosymbionts, whereas the parasites from the second locality were endosymbiont-free. This is a first case documenting presence of intracellular symbiotic bacteria in Phytomonas spp. We suggest that this novel endosymbiotic association arose very recently and did not become obligate yet. Further investigation of P. borealis and its intracellular bacteria may shed light on the origin and early evolution of endosymbiosis in trypanosomatids.

• Klíčová slova
• new trypanosomatid species, non-specific infection, prokaryotic endosymbionts,
• MeSH
• fylogeneze MeSH
• fyziologie bakterií * MeSH
• Heteroptera růst a vývoj   parazitologie   MeSH
• nymfa růst a vývoj   parazitologie   MeSH
• RNA protozoální analýza   MeSH
• RNA ribozomální 18S analýza   MeSH
• symbióza * MeSH
• Trypanosomatina klasifikace   mikrobiologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Rusko MeSH
• Názvy látek
• RNA protozoální MeSH
• RNA ribozomální 18S MeSH

Trypanosomatids of the genera Angomonas and Strigomonas (subfamily Strigomonadinae) have long been known to contain intracellular beta-proteobacteria, which provide them with many important nutrients such as haem, essential amino acids and vitamins. Recently, Kentomonas sorsogonicus, a divergent member of Strigomonadinae, has been described. Herein, we characterize the genome of its endosymbiont, Candidatus Kinetoplastibacterium sorsogonicusi. This genome is completely syntenic with those of other known Ca. Kinetoplastibacterium spp., but more reduced in size (~742 kb, compared with 810-833 kb, respectively). Gene losses are not concentrated in any hot-spots but are instead distributed throughout the genome. The most conspicuous loss is that of the haem-synthesis pathway. For long, removing haemin from the culture medium has been a standard procedure in cultivating trypanosomatids isolated from insects; continued growth was considered as an evidence of endosymbiont presence. However, we demonstrate that, despite bearing the endosymbiont, K. sorsogonicus cannot grow in culture without haem. Thus, the traditional test cannot be taken as a reliable criterion for the absence or presence of endosymbionts in trypanosomatid flagellates. It remains unclear why the ability to synthesize such an essential compound was lost in Ca. K. sorsogonicusi, whereas all other known bacterial endosymbionts of trypanosomatids retain them.

• Klíčová slova
• Endosymbiosis, Trypanosomatidae., genome evolution, genome reduction, haem synthesis,
• MeSH
• Betaproteobacteria účinky léků   genetika   růst a vývoj   MeSH
• biosyntetické dráhy MeSH
• fylogeneze MeSH
• genom bakteriální * MeSH
• hem metabolismus   farmakologie   MeSH
• sekvenční analýza DNA MeSH
• symbióza * MeSH
• Trypanosomatina mikrobiologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• hem MeSH

UNLABELLED: We describe a novel symbiotic association between a kinetoplastid protist, Novymonas esmeraldas gen. nov., sp. nov., and an intracytoplasmic bacterium, "Candidatus Pandoraea novymonadis" sp. nov., discovered as a result of a broad-scale survey of insect trypanosomatid biodiversity in Ecuador. We characterize this association by describing the morphology of both organisms, as well as their interactions, and by establishing their phylogenetic affinities. Importantly, neither partner is closely related to other known organisms previously implicated in eukaryote-bacterial symbiosis. This symbiotic association seems to be relatively recent, as the host does not exert a stringent control over the number of bacteria harbored in its cytoplasm. We argue that this unique relationship may represent a suitable model for studying the initial stages of establishment of endosymbiosis between a single-cellular eukaryote and a prokaryote. Based on phylogenetic analyses, Novymonas could be considered a proxy for the insect-only ancestor of the dixenous genus Leishmania and shed light on the origin of the two-host life cycle within the subfamily Leishmaniinae. IMPORTANCE: The parasitic trypanosomatid protist Novymonas esmeraldas gen. nov., sp. nov. entered into endosymbiosis with the bacterium "Ca. Pandoraea novymonadis" sp. nov. This novel and rather unstable interaction shows several signs of relatively recent establishment, qualifying it as a potentially unique transient stage in the increasingly complex range of eukaryotic-prokaryotic relationships.

• MeSH
• Burkholderiaceae klasifikace   cytologie   izolace a purifikace   fyziologie   MeSH
• fylogeneze MeSH
• symbióza * MeSH
• Trypanosomatina klasifikace   cytologie   genetika   mikrobiologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Ekvádor MeSH

Compared to their relatives, the diversity of endosymbiont-containing Trypanosomatidae remains under-investigated, with only two new species described in the past 25 years, bringing the total to six. The possible reasons for such a poor representation of this group are either their overall scarcity or susceptibility of their symbionts to antibiotics that are traditionally used for cultivation of flagellates. In this work we describe the isolation, cultivation, as well as morphological and molecular characterization of a novel endosymbiont-harboring trypanosomatid species, Kentomonas sorsogonicus sp. n. The newly erected genus Kentomonas gen. n. shares many common features with the genera Angomonas and Strigomonas, such as the presence of an extensive system of peripheral mitochondrial branches distorting the corset of subpellicular microtubules, large and loosely packed kinetoplast, and a rudimentary paraflagellar rod. Here we also propose to unite all endosymbiont-bearing trypanosomatids into the new subfamily Strigomonadinae subfam. n.

• Klíčová slova
• Kentomonas, Trypanosomatidae, bacterial endosymbionts, phylogeny.,
• MeSH
• Bayesova věta MeSH
• DNA bakterií izolace a purifikace   MeSH
• DNA virů izolace a purifikace   MeSH
• druhová specificita MeSH
• fylogeneze * MeSH
• klonování DNA MeSH
• modely genetické MeSH
• pravděpodobnostní funkce MeSH
• RNA protozoální genetika   MeSH
• RNA ribozomální 18S genetika   MeSH
• Sarcophagidae parazitologie   MeSH
• sekvenční analýza DNA MeSH
• symbióza genetika   MeSH
• Trypanosomatina klasifikace   izolace a purifikace   mikrobiologie   virologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA bakterií MeSH
• DNA virů MeSH
• RNA protozoální MeSH
• RNA ribozomální 18S MeSH