Luiz Fernando Carvalho-Kelly , Anita Leocadio Freitas-Mesquita , Michelle T.C. Nascimento , Claudia F. Dick , Eduarda de Souza-Maciel , Natalia C. Rochael , Elvira M. Saraiva , José Roberto Meyer-Fernandes
{"title":"Acanthamoeba castellanii trophozoites escape killing by neutrophil extracellular traps using their 3′-nucleotidase/nuclease activity","authors":"Luiz Fernando Carvalho-Kelly , Anita Leocadio Freitas-Mesquita , Michelle T.C. Nascimento , Claudia F. Dick , Eduarda de Souza-Maciel , Natalia C. Rochael , Elvira M. Saraiva , José Roberto Meyer-Fernandes","doi":"10.1016/j.ejop.2023.126032","DOIUrl":"10.1016/j.ejop.2023.126032","url":null,"abstract":"<div><p><em>Acanthamoeba castellanii</em> is a free-living amoeba that acts as an opportunistic pathogen for humans and is the pathogenic agent of Acanthamoeba keratitis (AK). <em>A. castellanii</em> may present as proliferative and infective trophozoites or as resistant cysts during their life cycle. The immune response against AK is still poorly explored; however, it is well established that macrophages and neutrophils play essential roles in controlling corneal infection during the disease outcome. The release of NETs is one of the innate immune strategies to prevent parasite infection, especially when neutrophils interact with microorganisms that are too large to be phagocytosed, which is the case for amoeba species. The present work demonstrated that <em>A. castellanii</em> trophozoites can trigger NET formation upon <em>in vitro</em> interaction with neutrophils. Using DNase as a control, we observed increased parasite survival after coinciding with neutrophils, which may be correlated with NET degradation. Indeed, <em>A. castellanii</em> trophozoites degrade the NET DNA scaffold. Molecular analysis confirmed the occurrence of a 3′-nucleotidase/nuclease (3′-NT/NU) in the <em>A. castellanii</em> genome. We also demonstrated that trophozoites exhibit significantly higher 3′-NT/NU activity than cysts, which cannot trigger NET release. Considering that previous studies indicated the pathological role of 3′-NT-/NU in parasite infection, we suggest that this enzyme may act as the mechanism of escape of <em>A. castellanii</em> trophozoites from NETs.</p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"91 ","pages":"Article 126032"},"PeriodicalIF":2.9,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72208918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eva Mazancová , Eliška Zadrobílková , Naoji Yubuki , Ivan Čepička
{"title":"Phylogenetic and morphological diversity of free-living diplomonads","authors":"Eva Mazancová , Eliška Zadrobílková , Naoji Yubuki , Ivan Čepička","doi":"10.1016/j.ejop.2023.126024","DOIUrl":"10.1016/j.ejop.2023.126024","url":null,"abstract":"<div><p><span><span>Diplomonadida is a </span>lineage<span> of anaerobic protists<span> belonging to Fornicata, Metamonada. Most diplomonads are endobiotic or parasitic, such as </span></span></span><span><em>Giardia</em><em> intestinalis</em></span><span>, which is a famous human pathogen, but several free-living species exist as well. Although it has been proposed that the free-living diplomonads are descendants of endobiotic organisms and thus interesting from the evolutionary point of view, they have been largely neglected. We obtained 58 cultures of free-living diplomonads belonging to four genera (</span><span><em>Hexamita</em></span>, <em>Trepomonas</em>, <em>Gyromonas</em>, and <em>Trimitus</em>) and six strains of endobiotic diplomonads and analyzed their SSU rRNA gene sequences. We also studied light-microscopic morphology of selected strains and the ultrastructure of <em>Trepomonas rotans</em><span> for the first time. Our phylogenetic analysis showed that the genus </span><em>Hexamita</em>, and, possibly, also the genus <em>Trepomonas</em>, are polyphyletic. <em>Trepomonas rotans</em>, which may represent a novel genus, is unique among Diplomonadida by having the cell covered in scales. Our results suggest that the evolution of the endobiotic life style and cell organization in diplomonads is more complicated than previously thought.</p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"91 ","pages":"Article 126024"},"PeriodicalIF":2.9,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41116513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tingting Ye , Wen Song , Yuqing Li , Khaled A.S. Al-Rasheid , Valentina Serra , Mingzhen Ma
{"title":"Morphology and phylogeny of four trachelocercid ciliates (Ciliophora, Karyorelictea, Trachelocercidae) from North China Sea, with description of a new species","authors":"Tingting Ye , Wen Song , Yuqing Li , Khaled A.S. Al-Rasheid , Valentina Serra , Mingzhen Ma","doi":"10.1016/j.ejop.2023.126025","DOIUrl":"10.1016/j.ejop.2023.126025","url":null,"abstract":"<div><p><span>Trachelocercids are common ciliates in marine sandy intertidal zones, however, only few species have been described using modern taxonomic techniques, with several earlier descriptions still lacking primary data, such as a detailed description of the oral ciliature. For this reason, systematics of the family Trachelocercidae Kent, 1881 resulted in paraphyletic genera and needs a critical revision. As an attempt to fill the gap of knowledge for this group, this study presents one new species description, </span><em>Tracheloraphis apodiscolor</em><span> n. sp., along with redescriptions of three lesser-known trachelocercid species, </span><em>Trachelocerca bodiani</em> (<span>Dragesco, 1963</span>) <span>Dragesco, 2002</span>, <em>Trachelocerca ditis</em> (<span>Wright, 1982</span>) <span>Foissner & Dragesco, 1996</span> and <em>Prototrachelocerca fasciolata</em> (<span>Sauerbrey, 1928</span>) <span>Foissner, 1996</span><span>, collected from coastal marine habitats at Qingdao (China), using live and protargol-stained specimens. </span><em>Tracheloraphis apodiscolor</em> n. sp. can be distinguished from its closest related congener, <em>T. discolor</em>, by a shorter body length and fewer somatic kineties. Molecular data of <em>T. apodiscolor</em> n. sp. and <em>T. bodiani</em> were provided for the first time. Additionally, based on the Qingdao populations, we provide improved diagnoses for <em>T. ditis</em> and <em>P. fasciolata</em><span><span>. Phylogenetic analyses were performed and discussed, as there is strong support for </span>paraphyly of the genera </span><em>Tracheloraphis</em> and <em>Trachelocerca</em>. In general, more integrative studies based on taxonomy, ultrastructure as well as molecular data are needed to properly shed light on the systematics of trachelocercids.</p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"91 ","pages":"Article 126025"},"PeriodicalIF":2.9,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"61561749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mahnaz Barmshuri , Ondřej Pomahač , William Bourland
{"title":"Enchelyothrix muria n. gen, n. sp., (Ciliophora, Litostomatea, Spathidiida), an extreme halotroph spathidiid from Maharloo Lake, Iran","authors":"Mahnaz Barmshuri , Ondřej Pomahač , William Bourland","doi":"10.1016/j.ejop.2023.126005","DOIUrl":"10.1016/j.ejop.2023.126005","url":null,"abstract":"<div><p><span><span>Although free-living ciliated protists<span> (Ciliophora) commonly inhabit aquatic and terrestrial biotopes of mild to moderate salinity (PSS-practical salinity scale S = 10–150), very few have adapted to life at more extreme salinities (>150 to saturation). Such extreme </span></span>halophiles<span><span> or halotrophs are of interest from the standpoints of evolution, cell physiology, ecology, and even </span>astrobiology. In this work, we present the morphology, 18S rRNA gene sequence, and </span></span>phylogenetic analysis<span> of a novel spathidiid ciliate (Ciliophora, Litosatomatea) that thrives in saturated brines of Maharloo Lake, Iran. Based on its unique combination of morphologic features, its molecular characterization, and its unusual ecology, it is assigned to a newly erected monotypic genus incertae sedis in order Spathidiida. The new species differs from other spathidiids by: a cell with a very short acutely pointed tail, the absence of a circumoral kinety with, instead, inclined, interrupted circumoral kinetofragments at the anterior end of somatic kineties and brush rows abutting the oral bulge, the absence of a contractile vacuole, a heteromorphic dorsal brush comprising five or six rows, and an extreme (at or near saturation) hypersaline habitat. We briefly discuss the persistent uncertainties regarding the phylogenetic relationships within the order Spathidiida.</span></p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"90 ","pages":"Article 126005"},"PeriodicalIF":2.9,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10207356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ke Xiao , Qiping Zhao , Haixia Wang, Shunhai Zhu, Hui Dong, Bing Huang, Hongyu Han
{"title":"Molecular characterization of methionine aminopeptidase1 from Eimeria tenella","authors":"Ke Xiao , Qiping Zhao , Haixia Wang, Shunhai Zhu, Hui Dong, Bing Huang, Hongyu Han","doi":"10.1016/j.ejop.2023.126012","DOIUrl":"10.1016/j.ejop.2023.126012","url":null,"abstract":"<div><p>Coccidiosis, a serious intestinal parasitic disease caused by <em>Eimeria</em> spp<em>.</em>, can result in huge annual economic losses to the poultry industry worldwide. At present, coccidiosis is mainly controlled by anticoccidial drugs. However, drug resistance has developed in <em>Eimeria</em> because of the long-term and unreasonable use of the drugs currently available. In our previous study, RNA-seq showed that the expression of methionine aminopeptidase1 (<em>Et</em>MetAP1) was up-regulated in diclazuril-resistant (DZR) and maduramicin-resistant (MRR) strains compared to drug-sensitive (DS) strain of <em>Eimeria tenella</em>. In this study, <em>Et</em>MetAP1 was cloned and expressed, and the function and characteristics of the <em>Et</em>MetAP1 protein were analyzed. The transcription and translation levels of <em>Et</em>MetAP1 in DS strain of <em>E. tenella</em> at different developmental stages were analyzed by qPCR and western blotting. We found that the transcription and translation levels of <em>Et</em>MetAP1 in second-generation merozoites (SM) were higher than those of the other three stages (unsporulated oocyst, sporulated oocyst, and sporozoites). Simultaneously, qPCR was used to analyze the mRNA transcription levels of <em>Et</em>MetAP1 in DS, DZR, MRR, and salinomycin-resistant (SMR) strain. The results showed that compared to the sensitive strain, the transcription levels of <em>Et</em>MetAP1 in DZR and MRR were up-regulated. There was no significant difference in transcription level in SMR. Indirect immunofluorescence localization showed that the protein was mainly localised in the cell membrane and cytoplasm of sporozoites and SM. An invasion inhibition test showed that anti-r<em>Et</em>MetAP1 polyclonal antibody could effectively inhibit the sporozoite invasion of host cells. These results suggest that the protein may be involved in the growth and development of parasites in host cells, the generation of drug resistance, and host cell invasion.</p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"90 ","pages":"Article 126012"},"PeriodicalIF":2.9,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10264150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sylvain Kreuter , Maria Holzmann , Diana Grace Holdsworth , Rozalia Motoc , Ana Bianca Pavel
{"title":"Three new species of Gromia (Protista, Rhizaria) identified from the Romanian Black Sea shelf","authors":"Sylvain Kreuter , Maria Holzmann , Diana Grace Holdsworth , Rozalia Motoc , Ana Bianca Pavel","doi":"10.1016/j.ejop.2023.126004","DOIUrl":"10.1016/j.ejop.2023.126004","url":null,"abstract":"<div><p><span>The protist genus </span><em>Gromia</em> was first described in 1835 by Dujardin and while gromiids are prominent in the marine environment, <em>Gromia oviformis</em> was, for a long time, the only valid species regularly recorded. To date, 16 species that are morphologically and/or genetically distinct have been described. While recent studies are documenting their diversity and their ecological importance, <em>G. oviformis</em> has been the sole gromiid species identified in the Black Sea, although unnamed <em>Gromia</em><span><span> species have also been recorded. We collected sediment samples from the Romanian continental shelf at varying depths (48 – 58 m) to study the morphological and </span>genetic diversity of gromiids in this part of the Black Sea. Three new species, </span><em>Gromia bugnae</em> sp. nov.<em>, Gromia dianae</em> sp. nov. and <em>Gromia fabi</em> sp. nov., were identified based on an integrative taxonomic approach, thus bringing the total described gromiid species to 19. Analysis of partial SSU rRNA gene sequences confirms that these are distinct species. Additionally, an undescribed species is represented by a sequence from the northern part of the Black Sea (Sevastopol, Kazachya Bay). The study provides further evidence of the diversity of gromiids in the Black Sea and underlines the importance of this little-known group in marginal seas.</p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"90 ","pages":"Article 126004"},"PeriodicalIF":2.9,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10210712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anna Bessudova , Viktor Gabyshev , Yelena V. Likhoshway
{"title":"Silica-scaled heterotrophic protists: Rotosphaerida, Thaumatomonadida and Centroplasthelida in Arctic waters of Russia","authors":"Anna Bessudova , Viktor Gabyshev , Yelena V. Likhoshway","doi":"10.1016/j.ejop.2023.125975","DOIUrl":"10.1016/j.ejop.2023.125975","url":null,"abstract":"<div><p><span>Maintaining high levels of biological diversity in various ecosystems is necessary for stable functioning of the Earth's biosphere. The article describes diversity and ecology of heterotrophic siliceous protists<span> – rotosphaerids, colourless free-living thaumatomonad flagellates, and centrohelid heliozoans – in Arctic waters located of Asian Russia. Samples were collected in the mouths of the Olenyok, Yana, Indigirka, Kolyma Rivers – and small freshwater ponds near Settlement of Tiksi in Yakutia. Based on electron microscopy, 35 centrohelids (Heliozoa), 11 rotosphaerid species as well as four thaumatomonad flagellate species were found in the region. Seven species were recorded in Russia for the first time: </span></span><em>Rabdiaster multicosta</em>, <em>Rabdiaster reticulata</em>, <em>Turriplaca denticulata</em>, <em>Choanocystis</em> cf. <em>cordiformis parvula</em>, <em>Raineriophrys pteromorphos</em>, <em>Pseudoraphidocystis glutinosa</em> and <em>Pseudoraphidiophrys formosa.</em> For 43 species, the study area is the most northern location they were described. Morphological details of scales are discussed for selected species, particularly for widespread species of rotosphaerids – <em>Pinaciophora fluviatilis.</em> The literature on hydrochemical conditions was analyzed to find taxa with high sensitivity towards environmental changes. Such species could be further used for monitoring plankton, recovering evolutionary changes, and reconstructing past environments.</p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"90 ","pages":"Article 125975"},"PeriodicalIF":2.9,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10198592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kateřina Poláková, William A. Bourland, Ivan Čepička
{"title":"Anaerocyclidiidae fam. nov. (Oligohymenophorea, Scuticociliatia): A newly recognized major lineage of anaerobic ciliates hosting prokaryotic symbionts","authors":"Kateřina Poláková, William A. Bourland, Ivan Čepička","doi":"10.1016/j.ejop.2023.126009","DOIUrl":"10.1016/j.ejop.2023.126009","url":null,"abstract":"<div><p><span><span>The research on anaerobic ciliates, to date, has mainly been focused on representatives of obligately anaerobic classes such as Armophorea or Plagiopylea. In this study, we focus on the anaerobic representatives of the subclass Scuticociliatia, members of the class </span>Oligohymenophorea, which is mainly composed of aerobic ciliates. Until now, only a single anaerobic species, </span><em>Cyclidium porcatum</em> (here transferred to the genus <em>Anaerocyclidium</em><span><span> gen. nov.), has been described both molecularly and morphologically. Our broad sampling of anoxic sediments together with cultivation and single cell sequencing approaches have shown that scuticociliates are common and diversified in anoxic environments. Our results show that anaerobic scuticociliates represent a distinctive evolutionary lineage not closely related to the family Cyclidiidae (order Pleuronematida), as previously suggested. However, the </span>phylogenetic position of the newly recognized lineage within the subclass Scuticociliatia remains unresolved. Based on molecular and morphological data, we establish the family Anaerocyclidiidae fam. nov. to accommodate members of this clade. We further provide detailed morphological descriptions and 18S rRNA gene sequences for six new </span><em>Anaerocyclidium</em> species and significantly broaden the described diversity of anaerobic scuticociliates.</p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"90 ","pages":"Article 126009"},"PeriodicalIF":2.9,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10208440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anita Leocadio Freitas-Mesquita , Luiz Fernando Carvalho-Kelly , Thaís Souza Silveira Majerowicz , José Roberto Meyer-Fernandes
{"title":"Euglena gracilis: Biochemical properties of a membrane bound ecto-phosphatase activity modulated by fluoroaluminate complexes and different trophic conditions","authors":"Anita Leocadio Freitas-Mesquita , Luiz Fernando Carvalho-Kelly , Thaís Souza Silveira Majerowicz , José Roberto Meyer-Fernandes","doi":"10.1016/j.ejop.2023.126010","DOIUrl":"10.1016/j.ejop.2023.126010","url":null,"abstract":"<div><p>The ecto-phosphatases belong to a group of enzymes closely associated with the cell surface that has its catalytic site facing the extracellular environment, where different phosphorylated substrates can be hydrolyzed. In the present work, we biochemically characterized the ecto-phosphatase activity of the freshwater microalgae <em>Euglena gracilis</em>, a model microorganism, ubiquitously distributed and resistant to several environmental stressors. The ecto-phosphatase activity is acidic, stimulated by copper and presents the following apparent kinetic parameters: <em>K</em><sub>m</sub> = 2.52 ± 0.12 mM <em>p</em>-NPP and <em>V</em><sub>max</sub> = 3.62 ± 0.06 nmol <em>p</em>-NP × h<sup>−1</sup> × 10<sup>6</sup> cells. We observed that zinc, orthovanadate, molybdate, fluoride, and inorganic phosphate inhibit the ecto-phosphatase activity with different magnitudes. Fluoroaluminate complexes are also inhibitors of this ecto-phosphatase activity. They can be formed in the enzyme reaction conditions and are likely to occur in a natural environment where <em>E. gracilis</em> can be found. The ecto-phosphatase activity is constant through the culture growth phases and is negatively modulated after continuous subculturing in the dark when a shift from phototrophic to the heterotrophic metabolism is likely. The analysis of those biochemical parameters may contribute to understanding the role of <em>E. gracilis</em> ecto-phosphatase activity in natural environments.</p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"90 ","pages":"Article 126010"},"PeriodicalIF":2.9,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10199667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sergei I. Fokin , Natalia A. Lebedeva , Alexey Potekhin , Leandro Gammuto , Giulio Petroni , Valentina Serra
{"title":"Holospora-like bacteria “Candidatus Gortzia yakutica” and Preeria caryophila: Ultrastructure, promiscuity, and biogeography of the symbionts","authors":"Sergei I. Fokin , Natalia A. Lebedeva , Alexey Potekhin , Leandro Gammuto , Giulio Petroni , Valentina Serra","doi":"10.1016/j.ejop.2023.125998","DOIUrl":"10.1016/j.ejop.2023.125998","url":null,"abstract":"<div><p>Two already known representatives of <em>Holospora</em>-like bacteria, “<em>Candidatus</em> Gortzia yakutica” from <em>Paramecium putrinum</em> and <em>Preeria caryophila,</em> originally retrieved from the <em>Paramecium aurelia</em> complex, were found in new hosts: <em>Paramecium nephridiatum</em> and <em>Paramecium polycaryum</em>, respectively. In the present study, these bacteria were investigated using morphological and molecular methods. For “<em>Ca.</em> G. yakutica”, the first details of the electron microscopic structure in the main and new hosts were provided. Regarding <em>Pr. caryophila</em>, the ultrastructural description of this species was implemented by several features previously unknown, such as the so called “membrane cluster” dividing periplasm from cytoplasm and fine composition of infectious forms before and during its releasing from the infected macronucleus. The new combinations of these <em>Holospora</em>-like bacteria with ciliate hosts were discussed from biogeographical and ecological points of view. Host specificity of symbionts as a general paradigm was critically reviewed as well.</p></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"90 ","pages":"Article 125998"},"PeriodicalIF":2.9,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10204820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}