“Candidatus Fokinia solitaria”, a Novel “Stand-Alone” Symbiotic Lineage of Midichloriaceae (Rickettsiales)

Abstract

Recently, the family Midichloriaceae has been described within the bacterial order Rickettsiales. It includes a variety of bacterial endosymbionts detected in different metazoan host species belonging to Placozoa, Cnidaria, Arthropoda and Vertebrata. Representatives of Midichloriaceae are also considered possible etiological agents of certain animal diseases. Midichloriaceae have been found also in protists like ciliates and amoebae. The present work describes a new bacterial endosymbiont, “Candidatus Fokinia solitaria”, retrieved from three different strains of a novel Paramecium species isolated from a wastewater treatment plant in Rio de Janeiro (Brazil). Symbionts were characterized through the full-cycle rRNA approach: SSU rRNA gene sequencing and fluorescence in situ hybridization (FISH) with three species-specific oligonucleotide probes. In electron micrographs, the tiny rod-shaped endosymbionts (1.2 x 0.25–0.35 μm in size) were not surrounded by a symbiontophorous vacuole and were located in the peripheral host cytoplasm, stratified in the host cortex in between the trichocysts or just below them. Frequently, they occurred inside autolysosomes. Phylogenetic analyses of Midichloriaceae apparently show different evolutionary pathways within the family. Some genera, such as “Ca. Midichloria” and “Ca. Lariskella”, have been retrieved frequently and independently in different hosts and environmental surveys. On the contrary, others, such as Lyticum, “Ca. Anadelfobacter”, “Ca. Defluviella” and the presently described “Ca. Fokinia solitaria”, have been found only occasionally and associated to specific host species. These last are the only representatives in their own branches thus far. Present data do not allow to infer whether these genera, which we named “stand-alone lineages”, are an indication of poorly sampled organisms, thus underrepresented in GenBank, or represent fast evolving, highly adapted evolutionary lineages.

Disentangling the Taxonomy of Rickettsiales and Description of Two Novel Symbionts (“Candidatus Bealeia paramacronuclearis” and “Candidatus Fokinia cryptica”) Sharing the Cytoplasm of the Ciliate Protist Paramecium biaurelia

“…Touchdown PCR (31) was carried out with the Alphaproteobacteria-specific forward primer 16Sα_F19b and the Bacteria-specific reverse primer 16S_R1522a (32), as described by Szokoli and colleagues (33). PCR products were purified with the EuroGold CyclePure kit (EuroClone S.p.A. Headquarters and Marketing, Pero, Milan, Italy) and sequenced using internal primers (32).…”

“…Both probes were obtained from Eurofins Genomics GmbH (Ebersberg, Germany). Fluorescence in situ hybridization (FISH) was performed with each newly designed probe, in combination with EUB338 (fluorescein isothiocyanate [FITC] labeled at the 5′ end) (35), according to methods described by Szokoli and coworkers (33). Both probes were tested with formamide concentrations ranging from 0 to 50%.…”

“…Additionally, to discriminate the symbiont observed in isolate US_Bl 11III1 from the already-described “Candidatus Fokinia solitaria,” the previously published probes Fokinia_198, Fokinia_434, and Fokinia_1250 (33) were tested in silico and in FISH experiments for their binding to the SSU rRNA of the second endosymbiont from isolate US_Bl 11III1.…”

“Candidatus Gortzia shahrazadis”, a Novel Endosymbiont of Paramecium multimicronucleatum and a Revision of the Biogeographical Distribution of Holospora-Like Bacteria

“…Molecular characterization shows a large biodiversity among these symbionts (Irbis and Ushida, 2004; Vannini et al, 2004, 2010, 2014; Rinke et al, 2006; Schrallhammer et al, 2006, 2011, 2013; Ferrantini et al, 2009; Boscaro et al, 2012, 2013a,b,c; Gong et al, 2014; Senra et al, 2015; Szokoli et al, 2016) and also the type of interaction with their hosts can range from mutualistic to parasitic (Kusch et al, 2002; Vannini et al, 2003, 2007; Fels and Kaltz, 2006; Fellous et al, 2011). In this work, we use De Bary's definition of “symbiosys” (de Bary, 1879), as “the living together of two differently named organisms”, independent of effects on the organisms involved, thereby including mutualism, parasitism, and commensalism.…”

«candidatus Midichloria Mitochondrii»: A New Member of Order Rickettsiales, Endosymbiont of Ixodes Ricinus Tick

“…В настоящее время в семействе «Candidatus Midichloriaceae» выделено несколько родов «Candidatus Midichloria», «Candidatus Lariskel la», «Candidatus Anadelfobacter», «Candidatus Defluviella» и недавно описанный вид «Candidatus Fokinia solitaria», претендующий на статус рода [42].…”