Characterization of a Pseudokeronopsis Strain (Ciliophora, Urostylida) and Its Bacterial Endosymbiont “Candidatus Trichorickettsia” (Alphaproteobacteria, Rickettsiales)

Symbiotic associations between bacteria and ciliate protists are rather common. In particular, several cases were reported involving of the alphaproteobacterial lineage Rickettsiales, but diversity, features, interactions in these still poorly understood. this work, we characterized a novel protist strain originating from Brazil its associated Rickettsiales endosymbiont by means live ultrastructural observations, as well molecular phylogeny. Though with few morphological peculiarities, was found to be phylogenetically affiliated Pseudokeronopsis erythrina, euryhaline species, which is consistent origin lagoon significant spatial seasonal salinity variations. The bacterial symbiont assigned “Candidatus Trichorickettsia mobilis subsp. hyperinfectiva”, being first documented case urostylid ciliates. It resided host cytoplasm bore flagella, similarly many, not all, conspecifics other species. These findings highlight ability Trichorickettsia” infect multiple distinct species underline importance further studies on system, particular flagella their regulation, functional also an evolutionary perspective, considering phylogenetic proximity well-studied non-flagellated Rickettsia.