Pub Date : 2025-08-01Epub Date: 2025-07-23DOI: 10.1016/j.ejop.2025.126160
Rafael L. Macêdo , Odete Rocha
Functional traits provide key insights into ecological strategies and evolutionary diversification. In this study, we analyzed a comprehensive trait dataset to investigate morphological predictors of feeding ecology in testate amoebae from the Northern Holarctic realm, focusing on variability across 372 species. We also examined whether trait diversity mirrors taxonomic richness at the family level. Morphological traits included shell length, shell width, aperture dimensions, shape, and covering. The Principal Component Analysis (PCA) indicated that Axis 1 predominantly represented variation in shell and aperture size, while Axis 2 was associated with differences in overall shape proportions. Bacterivorous species exhibited the greatest morphological and taxonomic diversity, spanning 21 families and 48 genera, with mixotrophs and predators occupying nested subsets of their broader morphospace. The regression analyses demonstrated significant associations between species richness and variation in protective features, including aperture rim morphology and the presence of spines. Decision tree models identified the aperture width-to-length ratio as a key predictor of feeding strategy, although classification accuracy was lower for mixotrophs and predators. Future research should integrate shell morphology with phylogenetic data to enhance ecological strategy predictions in testate amoebae and explore hypotheses regarding functional diversification across a broader geographical scale and within different environments.
{"title":"Trait-based predictors of feeding ecology patterns in shelled microorganisms","authors":"Rafael L. Macêdo , Odete Rocha","doi":"10.1016/j.ejop.2025.126160","DOIUrl":"10.1016/j.ejop.2025.126160","url":null,"abstract":"<div><div>Functional traits provide key insights into ecological strategies and evolutionary diversification. In this study, we analyzed a comprehensive trait dataset to investigate morphological predictors of feeding ecology in testate amoebae from the Northern Holarctic realm, focusing on variability across 372 species. We also examined whether trait diversity mirrors taxonomic richness at the family level. Morphological traits included shell length, shell width, aperture dimensions, shape, and covering. The Principal Component Analysis (PCA) indicated that Axis 1 predominantly represented variation in shell and aperture size, while Axis 2 was associated with differences in overall shape proportions. Bacterivorous species exhibited the greatest morphological and taxonomic diversity, spanning 21 families and 48 genera, with mixotrophs and predators occupying nested subsets of their broader morphospace. The regression analyses demonstrated significant associations between species richness and variation in protective features, including aperture rim morphology and the presence of spines. Decision tree models identified the aperture width-to-length ratio as a key predictor of feeding strategy, although classification accuracy was lower for mixotrophs and predators. Future research should integrate shell morphology with phylogenetic data to enhance ecological strategy predictions in testate amoebae and explore hypotheses regarding functional diversification across a broader geographical scale and within different environments.</div></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"100 ","pages":"Article 126160"},"PeriodicalIF":1.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144711725","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}
Pub Date : 2025-08-01Epub Date: 2025-07-30DOI: 10.1016/j.ejop.2025.126164
Andrej Jedlička , Olivier Barth , Diana Lihanová Bugajdová , Terézia Beck , Vanessa Gelanová , Juraj Krajčovič , Dominika Vešelényiová , Matej Vesteg
Euglenids typically reproduce asexually by closed intranuclear orthomitosis and longitudinal cell division. The nucleus divides without the dissolution of the nuclear envelope, and the spindle is radially symmetric. Typical longitudinal cell division begins in the reservoir at the anterior end of the cell and the shape of the dividing cell gradually changes from a “Y” to a “V”. This paper reviews typical mitosis and cytokinesis in euglenids, alongside atypical cell division, in which a single cell produces more than two daughter cells, forming distinctive star-like structures. Atypical cell division is particularly observed under specific stress conditions, such as exposure to chemical substances (e.g., phenol and xylene), and in senescent cultures. Although euglenids are generally considered to be asexual, the presence of key meiotic genes in Euglena gracilis suggests the potential for sexual reproduction. Bioinformatic analyses and experimental approaches, including flow cytometry and fluorescence in situ hybridization (FISH), are discussed as potential methods for detecting meiosis, sex, and cell fusion in euglenids. This review contributes to a broader understanding of both typical and atypical cell division in euglenids and underscores the need for further research into these processes, including the possible occurrence of meiosis and sexual reproduction.
{"title":"Typical and atypical cell division versus potential meiosis and sex in euglenids","authors":"Andrej Jedlička , Olivier Barth , Diana Lihanová Bugajdová , Terézia Beck , Vanessa Gelanová , Juraj Krajčovič , Dominika Vešelényiová , Matej Vesteg","doi":"10.1016/j.ejop.2025.126164","DOIUrl":"10.1016/j.ejop.2025.126164","url":null,"abstract":"<div><div>Euglenids typically reproduce asexually by closed intranuclear orthomitosis and longitudinal cell division. The nucleus divides without the dissolution of the nuclear envelope, and the spindle is radially symmetric. Typical longitudinal cell division begins in the reservoir at the anterior end of the cell and the shape of the dividing cell gradually changes from a “Y” to a “V”. This paper reviews typical mitosis and cytokinesis in euglenids, alongside atypical cell division, in which a single cell produces more than two daughter cells, forming distinctive star-like structures. Atypical cell division is particularly observed under specific stress conditions, such as exposure to chemical substances (e.g., phenol and xylene), and in senescent cultures. Although euglenids are generally considered to be asexual, the presence of key meiotic genes in <em>Euglena gracilis</em> suggests the potential for sexual reproduction. Bioinformatic analyses and experimental approaches, including flow cytometry and fluorescence in situ hybridization (FISH), are discussed as potential methods for detecting meiosis, sex, and cell fusion in euglenids. This review contributes to a broader understanding of both typical and atypical cell division in euglenids and underscores the need for further research into these processes, including the possible occurrence of meiosis and sexual reproduction.</div></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"100 ","pages":"Article 126164"},"PeriodicalIF":1.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144771719","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}
Pub Date : 2025-08-01Epub Date: 2025-08-21DOI: 10.1016/j.ejop.2025.126165
Dmitry G. Zagumyonnyi , German A. Sozonov , Elena A. Gerasimova , Artem O. Belyaev , Olga N. Zagumyonnaya , Elizaveta E. Makarenko , Ruslan Kasseinov , Denis V. Tikhonenkov
Soil protists play key roles in terrestrial ecosystems, influencing microbial dynamics, nutrient cycling, and plant health. In this study, we describe a new genus and species of centrohelid heliozoans, Tellocystis perplexa gen. et sp. nov. and Raphidocystis akmolaensis sp. nov., isolated from agricultural soil habitats, and characterize two other known cyst-forming centrohelid species from soil. T. perplexa gen. et sp. nov., studied using light and electron microscopy, possesses an unusual spine-scale morphology, featuring a small drop-shaped basal plate and a curved shaft. Phylogenetic analysis of the 18S rRNA gene unexpectedly placed this species within the clade previously referred to as ‘Pinaciophora’, which is nested within Pterista, alongside unpublished clones of ‘Choanocystis perpusilla’ from Franz Josef Land and Southern Transbaikalia. Based on the obtained data, we transferred C. perpusilla to the genus Tellocystis. R. akmolaensis sp. nov. is morphologically similar to R. symmetrica, but differs from it by having smaller cell and plate-scale sizes, and by formation of cyst scales that are distinct from those of its trophic phase. Phylogenetic analysis indicated that this species occupies a deep evolutionary position within Raphidocystidae, basal to R. symmetrica, R. tubifera, R. ambigua, and ‘R. brunii’. This study advances current knowledge of the diversity of soil heterotrophic protists, which play an essential role in regulating microbial populations, and clarifies the intricate taxonomy of some centrohelid heliozoans.
土壤原生生物在陆地生态系统中发挥着关键作用,影响着微生物动力学、养分循环和植物健康。在本研究中,我们描述了从农业土壤生境中分离到的一个新属和新种:Tellocystis perplexa . et sp. 11和Raphidocystis akmolaensis sp. nov.,并对另外两个已知的从土壤中分离到的形成囊状的centrohelids物种进行了表征。使用光镜和电子显微镜研究的T. perplexa gen. et sp. nov.具有不寻常的脊柱鳞片形态,具有小水滴状的基底和弯曲的轴。18S rRNA基因的系统发育分析出乎意料地将该物种置于以前被称为“Pinaciophora”的进化枝中,该进化枝嵌套在Pterista中,与来自Franz Josef Land和南外贝卡拉的“Choanocystis perpusilla”的未发表克隆一起。根据获得的资料,我们将C. perpusilla转移到Tellocystis属。akmolaensis sp. 11 .在形态上与对称r.s ametrica相似,但不同之处在于其细胞和板级尺寸较小,并且形成与营养期不同的囊肿鳞片。系统发育分析表明,该种在Raphidocystidae中处于较深的进化位置,属于对称鼠属、管形鼠属、双歧鼠属和' R。brunii”。本研究进一步提高了对土壤异养原生生物多样性的认识,并澄清了一些中心体日生动物的复杂分类。
{"title":"Novel taxa of the centrohelid heliozoans (Pterocystida and Panacanthocystida) from agricultural soils","authors":"Dmitry G. Zagumyonnyi , German A. Sozonov , Elena A. Gerasimova , Artem O. Belyaev , Olga N. Zagumyonnaya , Elizaveta E. Makarenko , Ruslan Kasseinov , Denis V. Tikhonenkov","doi":"10.1016/j.ejop.2025.126165","DOIUrl":"10.1016/j.ejop.2025.126165","url":null,"abstract":"<div><div>Soil protists play key roles in terrestrial ecosystems, influencing microbial dynamics, nutrient cycling, and plant health. In this study, we describe a new genus and species of centrohelid heliozoans, <em>Tellocystis perplexa</em> gen. et sp. nov. and <em>Raphidocystis akmolaensis</em> sp. nov., isolated from agricultural soil habitats, and characterize two other known cyst-forming centrohelid species from soil. <em>T. perplexa</em> gen. et sp. nov., studied using light and electron microscopy, possesses an unusual spine-scale morphology, featuring a small drop-shaped basal plate and a curved shaft. Phylogenetic analysis of the 18S rRNA gene unexpectedly placed this species within the clade previously referred to as ‘<em>Pinaciophora</em>’, which is nested within Pterista, alongside unpublished clones of ‘<em>Choanocystis perpusilla</em>’ from Franz Josef Land and Southern Transbaikalia. Based on the obtained data, we transferred <em>C. perpusilla</em> to the genus <em>Tellocystis</em>. <em>R. akmolaensis</em> sp. nov. is morphologically similar to <em>R. symmetrica</em>, but differs from it by having smaller cell and plate-scale sizes, and by formation of cyst scales that are distinct from those of its trophic phase. Phylogenetic analysis indicated that this species occupies a deep evolutionary position within Raphidocystidae, basal to <em>R. symmetrica</em>, <em>R. tubifera</em>, <em>R. ambigua</em>, and ‘<em>R. brunii</em>’. This study advances current knowledge of the diversity of soil heterotrophic protists, which play an essential role in regulating microbial populations, and clarifies the intricate taxonomy of some centrohelid heliozoans.</div></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"100 ","pages":"Article 126165"},"PeriodicalIF":1.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144922019","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}
Pub Date : 2025-08-01Epub Date: 2025-07-28DOI: 10.1016/j.ejop.2025.126163
Ji Hye Moon, Atef Omar, Jae-Ho Jung
The morphology and multi-gene phylogeny of Rubrioxytricha hasllaensis n. sp., a non-oxytrichid dorsomarginalian ciliate discovered in a brackish water habitat in South Korea, were investigated. The new species is characterized by a body size of 125-145 × 30-40 μm in vivo, colorless cytoplasm, yellow cortical granules, 30-36 adoral membranelles, 25-35 left and 25-38 right marginal cirri, a single caudal cirrus, and undulating membranes distinctly curved leftward. In phylogenetic analyses based on 18S rRNA gene sequences, the new species clusters with other Rubrioxytricha species, forming a monophyletic clade that groups with members of the genera Polystichothrix, Pseudogastrostyla, Pseudocyrtohymena, and Pseudocyrtohymenides. In phylogenetic analyses using concatenated 18S-ITS1-5.8S-ITS2 and partial 28S rRNA gene sequences, newly obtained sequences from Rubrioxytricha, Pseudocyrtohymena, and Pseudocyrtohymenides form a sister clade to the assemblage of soft-bodied hypotrichs possessing dorsal kinety fragmentation. In addition to identifying morphological apomorphies shared by Rubrioxytricha and its phylogenetically related genera, including the absence of dorsal kinety fragmentation, a reduced number of caudal cirri, and the presence of a bipolar dorsomarginal kinety, new generic characters are introduced for dorsomarginalian hypotrichs and used to improve the diagnosis of the genus Rubrioxytricha.
{"title":"Morphology and multi-gene phylogeny of Rubrioxytricha hasllaensis n. sp. (Ciliophora, Spirotrichea) from South Korea.","authors":"Ji Hye Moon, Atef Omar, Jae-Ho Jung","doi":"10.1016/j.ejop.2025.126163","DOIUrl":"10.1016/j.ejop.2025.126163","url":null,"abstract":"<p><p>The morphology and multi-gene phylogeny of Rubrioxytricha hasllaensis n. sp., a non-oxytrichid dorsomarginalian ciliate discovered in a brackish water habitat in South Korea, were investigated. The new species is characterized by a body size of 125-145 × 30-40 μm in vivo, colorless cytoplasm, yellow cortical granules, 30-36 adoral membranelles, 25-35 left and 25-38 right marginal cirri, a single caudal cirrus, and undulating membranes distinctly curved leftward. In phylogenetic analyses based on 18S rRNA gene sequences, the new species clusters with other Rubrioxytricha species, forming a monophyletic clade that groups with members of the genera Polystichothrix, Pseudogastrostyla, Pseudocyrtohymena, and Pseudocyrtohymenides. In phylogenetic analyses using concatenated 18S-ITS1-5.8S-ITS2 and partial 28S rRNA gene sequences, newly obtained sequences from Rubrioxytricha, Pseudocyrtohymena, and Pseudocyrtohymenides form a sister clade to the assemblage of soft-bodied hypotrichs possessing dorsal kinety fragmentation. In addition to identifying morphological apomorphies shared by Rubrioxytricha and its phylogenetically related genera, including the absence of dorsal kinety fragmentation, a reduced number of caudal cirri, and the presence of a bipolar dorsomarginal kinety, new generic characters are introduced for dorsomarginalian hypotrichs and used to improve the diagnosis of the genus Rubrioxytricha.</p>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"100 ","pages":"126163"},"PeriodicalIF":1.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144811922","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}
We present the first survey of nivicolous myxomycetes (plasmodial slime molds, Amoebozoa) conducted in Kazakhstan, specifically from the Ile-Alatau mountain range near Almaty. A total of 82 specimens were collected, and 16 species were identified using a comparative morphological approach. Except for Didymium dubium, all identified species represent first records for Kazakhstan. DNA barcoding confirmed the morphology-based identification of 70 specimens, revealing 26 distinct barcode sequence variants. Among these, nine 18S rDNA barcode variants were novel and have not been previously reported in the GenBank database.
{"title":"First records of nivicolous myxomycetes (Amoebozoa) from Kazakhstan","authors":"Zhansaya Azirakhmet , Oleg Shchepin , Maho Inoue , Assiya Kussainova , Rakhmetkazhy Bersimbaev , Martin Schnittler","doi":"10.1016/j.ejop.2025.126161","DOIUrl":"10.1016/j.ejop.2025.126161","url":null,"abstract":"<div><div>We present the first survey of nivicolous myxomycetes (plasmodial slime molds, Amoebozoa) conducted in Kazakhstan, specifically from the Ile-Alatau mountain range near Almaty. A total of 82 specimens were collected, and 16 species were identified using a comparative morphological approach. Except for <em>Didymium dubium</em>, all identified species represent first records for Kazakhstan. DNA barcoding confirmed the morphology-based identification of 70 specimens, revealing 26 distinct barcode sequence variants. Among these, nine 18S rDNA barcode variants were novel and have not been previously reported in the GenBank database.</div></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"100 ","pages":"Article 126161"},"PeriodicalIF":1.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144766916","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}
Pub Date : 2025-08-01Epub Date: 2025-05-28DOI: 10.1016/j.ejop.2025.126155
Wenbao Zhuang , Xiaochen Feng , Ran Li , Xiaozhong Hu
The order Metopida is a species-rich taxon within the obligate anaerobic ciliate class Armophorea. Metopids have garnered increasing interest due to their potential to shed light on mitochondrial evolution and symbiotic relationship between eukaryotes and prokaryotes. However, the majority of metopid species remain poorly or incompletely studied, largely due to limitations in earlier research methodologies. In this study, three species, Bothrostoma aporobustum nov. spec., Brachonella mitriformis and Planometopus contractus, were examined using a morpho-molecular approach. The new species is distinguished by a short proboscis-shaped snout, an average of 33 somatic kineties, and 21 adoral membranelles. Brachonella mitriformis is characterized by a broad obpyriform body with a narrow and flattened posterior end, an average of 53 somatic kineties and 77 adoral membranelles, and unevenly distributed dikinetids on the preoral dome. Phylogenetic analyses confirmed the validity and monophyly of the genera Bothrostoma and Brachonella, and robustly resolved the phylogenetic position of Brachonella mitriformis. Representatives of geographically distant populations of Planometopus contractus are morphologically highly similar and cluster together with strong support in SSU rRNA gene phylogenies.
{"title":"Molecular phylogeny and taxonomy of three anaerobic ciliates including Bothrostoma aporobustum nov. spec. (Ciliophora, Metopida)","authors":"Wenbao Zhuang , Xiaochen Feng , Ran Li , Xiaozhong Hu","doi":"10.1016/j.ejop.2025.126155","DOIUrl":"10.1016/j.ejop.2025.126155","url":null,"abstract":"<div><div>The order Metopida is a species-rich taxon within the obligate anaerobic ciliate class Armophorea. Metopids have garnered increasing interest due to their potential to shed light on mitochondrial evolution and symbiotic relationship between eukaryotes and prokaryotes. However, the majority of metopid species remain poorly or incompletely studied, largely due to limitations in earlier research methodologies. In this study, three species, <em>Bothrostoma aporobustum</em> nov. spec., <em>Brachonella mitriformis</em> and <em>Planometopus contractus</em>, were examined using a morpho-molecular approach. The new species is distinguished by a short proboscis-shaped snout, an average of 33 somatic kineties, and 21 adoral membranelles. <em>Brachonella mitriformis</em> is characterized by a broad obpyriform body with a narrow and flattened posterior end, an average of 53 somatic kineties and 77 adoral membranelles, and unevenly distributed dikinetids on the preoral dome. Phylogenetic analyses confirmed the validity and monophyly of the genera <em>Bothrostoma</em> and <em>Brachonella</em>, and robustly resolved the phylogenetic position of <em>Brachonella mitriformis</em>. Representatives of geographically distant populations of <em>Planometopus contractus</em> are morphologically highly similar and cluster together with strong support in SSU rRNA gene phylogenies.</div></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"100 ","pages":"Article 126155"},"PeriodicalIF":1.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144331472","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}
Pub Date : 2025-08-01Epub Date: 2025-07-24DOI: 10.1016/j.ejop.2025.126162
Hongzhen Jiang , Haicheng Li , Chundi Wang , Yuanyuan Wang , Yongqiang Liu
Proliferating cell nuclear antigen (PCNA) is a central scaffold in eukaryotic DNA replication, repair, and epigenetic regulation. While its roles are well-characterized in canonical model organisms, ciliates, unicellular eukaryotes with nuclear dimorphism and programmed genome remodeling, offer unparalleled insights into PCNA's functional adaptability. Their unique biology, including replication-coupled DNA elimination, macronuclear amplification, and replication band dynamics, positions PCNA at the intersection of genome stability and plasticity. This review systematically compares ciliate and human PCNA through phylogenetic, structural, and functional analyses. We reveal that ciliate PCNAs, despite ∼50 % sequence divergence from mammals, preserve conserved trimerization interfaces and partner-binding motifs, as validated by AlphaFold3-predicted models of the classical model organism Tetrahymena thermophila and the emerging systems Euplotes eurystomus and Stylonychia lemnae. Functional summaries highlight lineage-specific innovations, including epigenetic regulation, paralog specialization for nuclear differentiation, and replication band assembly. These findings have broader implications for elucidating replication-coupled chromatin dynamics, the adaptive evolution of multiprotein complexes, and the use of non-model organisms such as E. eurystomus and S. lemnae to uncover conserved principles of genome biology.
{"title":"PCNA's dual legacy in ciliates: Conserved replication scaffold and lineage-specific genome architect","authors":"Hongzhen Jiang , Haicheng Li , Chundi Wang , Yuanyuan Wang , Yongqiang Liu","doi":"10.1016/j.ejop.2025.126162","DOIUrl":"10.1016/j.ejop.2025.126162","url":null,"abstract":"<div><div>Proliferating cell nuclear antigen (PCNA) is a central scaffold in eukaryotic DNA replication, repair, and epigenetic regulation. While its roles are well-characterized in canonical model organisms, ciliates, unicellular eukaryotes with nuclear dimorphism and programmed genome remodeling, offer unparalleled insights into PCNA's functional adaptability. Their unique biology, including replication-coupled DNA elimination, macronuclear amplification, and replication band dynamics, positions PCNA at the intersection of genome stability and plasticity. This review systematically compares ciliate and human PCNA through phylogenetic, structural, and functional analyses. We reveal that ciliate PCNAs, despite ∼50 % sequence divergence from mammals, preserve conserved trimerization interfaces and partner-binding motifs, as validated by AlphaFold3-predicted models of the classical model organism <em>Tetrahymena thermophila</em> and the emerging systems <em>Euplotes eurystomus</em> and <em>Stylonychia lemnae</em>. Functional summaries highlight lineage-specific innovations, including epigenetic regulation, paralog specialization for nuclear differentiation, and replication band assembly. These findings have broader implications for elucidating replication-coupled chromatin dynamics, the adaptive evolution of multiprotein complexes, and the use of non-model organisms such as <em>E. eurystomus</em> and <em>S. lemnae</em> to uncover conserved principles of genome biology.</div></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"100 ","pages":"Article 126162"},"PeriodicalIF":1.6,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144722158","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}
Pub Date : 2025-08-01Epub Date: 2025-07-07DOI: 10.1016/j.ejop.2025.126159
Savelii A. Poluzerov , Sofiya V. Dmitrovskaya
Acanthocystis turfacea Carter, 1863 is the type species of the centrohelid genus Acanthocystis Carter, 1863, which is characterized by bifurcated spine scales. In this study, the organism reported under the name A. turfacea by Zlatogursky and Klimov (2016) is reidentified as A. hymenodes Nicholls, 2023, based on morphological and morphometric evidence. Additionally, a centrohelid with a small cell diameter (7.9–11.9 μm) and distinctive scales, previously attributed to A. turfacea, was isolated from a marine habitat and is described here as a new species, Acanthocystis pohjolensis n. sp. Molecular phylogenetic analysis based on 18S rRNA gene sequences places A. pohjolensis and A. hymenodes in a basal position within the genus Acanthocystis, suggesting that bifurcated spine scales are likely an ancestral trait of this genus. Furthermore, the taxonomic status of A. turfacea ssp. decidens Nicholls, 2023 is revised and elevated to species level as A. decidens Nicholls, 2023 n. stat. The A. turfacea species complex is revisited.
{"title":"Revision of the Acanthocystis turfacea species complex, description of Acanthocystis pohjolensis n. sp. and notes on the phylogeny of Acanthocystis","authors":"Savelii A. Poluzerov , Sofiya V. Dmitrovskaya","doi":"10.1016/j.ejop.2025.126159","DOIUrl":"10.1016/j.ejop.2025.126159","url":null,"abstract":"<div><div><em>Acanthocystis turfacea</em> Carter, 1863 is the type species of the centrohelid genus <em>Acanthocystis</em> Carter, 1863, which is characterized by bifurcated spine scales. In this study, the organism reported under the name <em>A. turfacea</em> by Zlatogursky and Klimov (2016) is reidentified as <em>A. hymenodes</em> Nicholls, 2023, based on morphological and morphometric evidence. Additionally, a centrohelid with a small cell diameter (7.9–11.9 μm) and distinctive scales, previously attributed to <em>A. turfacea</em>, was isolated from a marine habitat and is described here as a new species, <em>Acanthocystis pohjolensis</em> n. sp. Molecular phylogenetic analysis based on 18S rRNA gene sequences places <em>A. pohjolensis</em> and <em>A. hymenodes</em> in a basal position within the genus <em>Acanthocystis</em>, suggesting that bifurcated spine scales are likely an ancestral trait of this genus. Furthermore, the taxonomic status of <em>A. turfacea</em> ssp. <em>decidens</em> Nicholls, 2023 is revised and elevated to species level as <em>A. decidens</em> Nicholls, 2023 n. stat. The <em>A. turfacea</em> species complex is revisited.</div></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"100 ","pages":"Article 126159"},"PeriodicalIF":1.9,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144703874","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}
Ciliates produce diffusible, cell-type-specific pheromones to regulate growth and mating. In Euplotes, these signaling molecules belong to species-specific families of disulfide-rich and structurally homologous proteins. Pheromones are co-dominantly expressed by genes in the somatic macronucleus (MAC), whereas their allelic diversity originates from the mating type locus in the germline micronucleus (MIC). During MAC development in sexual process, the MIC-derived diversity of specific alleles is rearranged via macronucleus-destined sequences (MDSs) assembly. While many MAC pheromones are well characterized, their MIC precursors and rearrangement process remain unknown. Here, we identified two MAC pheromone genes (mac-er-13/14) of E. raikovi, and two MIC regions (19 kb in total) containing 10 MDSs that assemble into mac-er-13. These MDSs are separated by internal eliminated sequences (234–3345 bp). The shortest MDSs (9–36 bp) encode the secreted region of pheromone, while longer MDSs (44–419 bp) encode other regions. Considering that the secreted regions show a higher sequence variation and the shorter MDSs have higher probability of alternative processing or imprecise assembly, we hypothesize that the high sequence variability of the macronuclear pheromone genes, which underlies the large number of mating types in E. raikovi, may result from alternative processing or imprecise assembly of these short MDSs.
{"title":"Characterization of the macronuclear and micronuclear pheromone genes of Euplotes raikovi reveals the origin of the mating type genetic diversity","authors":"Jianjun Huang , Ruitao Gong , Khaled A.S. Al-Rasheid , Feng Gao , Adriana Vallesi , Yaohan Jiang","doi":"10.1016/j.ejop.2025.126146","DOIUrl":"10.1016/j.ejop.2025.126146","url":null,"abstract":"<div><div>Ciliates produce diffusible, cell-type-specific pheromones to regulate growth and mating. In <em>Euplotes</em>, these signaling molecules belong to species-specific families of disulfide-rich and structurally homologous proteins. Pheromones are co-dominantly expressed by genes in the somatic macronucleus (MAC), whereas their allelic diversity originates from the <em>mating type locus</em> in the germline micronucleus (MIC). During MAC development in sexual process, the MIC-derived diversity of specific alleles is rearranged via macronucleus-destined sequences (MDSs) assembly. While many MAC pheromones are well characterized, their MIC precursors and rearrangement process remain unknown. Here, we identified two MAC pheromone genes (<em>mac-er-13/14</em>) of <em>E. raikovi</em>, and two MIC regions (19 kb in total) containing 10 MDSs that assemble into <em>mac-er-13</em>. These MDSs are separated by internal eliminated sequences (234–3345 bp). The shortest MDSs (9–36 bp) encode the secreted region of pheromone, while longer MDSs (44–419 bp) encode other regions. Considering that the secreted regions show a higher sequence variation and the shorter MDSs have higher probability of alternative processing or imprecise assembly, we hypothesize that the high sequence variability of the macronuclear pheromone genes, which underlies the large number of mating types in <em>E. raikovi</em>, may result from alternative processing or imprecise assembly of these short MDSs.</div></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"99 ","pages":"Article 126146"},"PeriodicalIF":1.9,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143747533","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}
Pub Date : 2025-06-01Epub Date: 2025-03-07DOI: 10.1016/j.ejop.2025.126140
Renate Radek , Janneke Hassler , Katja Platt , Hisar Ahmad , Thomas Fromm , Michaela Strüder-Kypke , David Sillam-Dussès , Jiří Synek , Jan Šobotník , Vincent Hervé , Andreas Brune
Sessilids (Oligohymenophorea, Peritrichia, Sessilida) reportedly colonize the gut of certain “higher termites” (family Termitidae), but only a single species, Termitophrya africana from Jugositermes tuberculatus (subfamily Apicotermitinae), has been described based on a drawing. Similar ciliates were observed in other Apicotermitinae but remained unspecified. Our SSU rRNA gene-based survey of peritrich ciliates in a broad range of Termitidae recovered distinct phylotypes from several Apicotermitinae (Astalotermes, Jugositermes, and Phoxotermes), albeit only from samples collected in Cameroon and not from all species of these genera. They form a monophyletic group in the family Epistylididae (Sessilida), with Orborhabdostyla bromelicola as the closest relative. Light, scanning, and transmission electron microscopy of the sessilid ciliates in J. tuberculatus revealed two morphotypes, which were assigned to their corresponding phylotypes by sequence analysis of capillary-picked single cells. One morphotype, which is highly contractile and broadens continuously towards the posterior end, matches the description of Termitophrya africana. The cells are attached by a posterior scopula with short cilia and are often covered with rod-shaped ectobionts. The other morphotype has a stockier, barrel-shaped body and a short, clearly demarcated anterior end and is always free of ectobionts. We designate it as Doliophrys denislynni gen. nov., sp. nov.
{"title":"Phylogeny, morphology, and ultrastructure of sessilid peritrich ciliates in termite guts, Termitophrya africana and Doliophrys denislynni gen. nov., sp. nov.","authors":"Renate Radek , Janneke Hassler , Katja Platt , Hisar Ahmad , Thomas Fromm , Michaela Strüder-Kypke , David Sillam-Dussès , Jiří Synek , Jan Šobotník , Vincent Hervé , Andreas Brune","doi":"10.1016/j.ejop.2025.126140","DOIUrl":"10.1016/j.ejop.2025.126140","url":null,"abstract":"<div><div>Sessilids (Oligohymenophorea, Peritrichia, Sessilida) reportedly colonize the gut of certain “higher termites” (family Termitidae), but only a single species, <em>Termitophrya africana</em> from <em>Jugositermes tuberculatus</em> (subfamily Apicotermitinae), has been described based on a drawing. Similar ciliates were observed in other Apicotermitinae but remained unspecified<em>.</em> Our SSU rRNA gene-based survey of peritrich ciliates in a broad range of Termitidae recovered distinct phylotypes from several Apicotermitinae (<em>Astalotermes</em>, <em>Jugositermes</em>, and <em>Phoxotermes</em>), albeit only from samples collected in Cameroon and not from all species of these genera. They form a monophyletic group in the family Epistylididae (Sessilida), with <em>Orborhabdostyla bromelicola</em> as the closest relative. Light, scanning, and transmission electron microscopy of the sessilid ciliates in <em>J. tuberculatus</em> revealed two morphotypes, which were assigned to their corresponding phylotypes by sequence analysis of capillary-picked single cells. One morphotype, which is highly contractile and broadens continuously towards the posterior end, matches the description of <em>Termitophrya africana</em>. The cells are attached by a posterior scopula with short cilia and are often covered with rod-shaped ectobionts. The other morphotype has a stockier, barrel-shaped body and a short, clearly demarcated anterior end and is always free of ectobionts. We designate it as <em>Doliophrys denislynni</em> gen. nov., sp. nov.</div></div>","PeriodicalId":12042,"journal":{"name":"European journal of protistology","volume":"99 ","pages":"Article 126140"},"PeriodicalIF":1.9,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143704986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}