Protist最新文献

{"title":"The enigmatic genus Malacophrys Kahl, 1926 (Ciliophora: Intramacronucleata) belongs to the class Oligohymenophorea","authors":"William Bourland,&nbsp;Ivan Čepička","doi":"10.1016/j.protis.2025.126089","DOIUrl":"10.1016/j.protis.2025.126089","url":null,"abstract":"<div><div>The ciliate genus <em>Malacophrys</em> has been incertae sedis for more than 50 years in what is now subphylum Intramacronucleata, provisionally assigned to three different classes by various authors. Of the three species included in the genus, <em>M. sphagni</em> and the type species, <em>Malacophrys rotans</em>, have not been studied by modern methods and <em>M. viridis</em>, although morphologically well-described, lacks molecular characterization. We identified two freshwater ciliates as morphologically consistent with two members of <em>Malacophrys</em>, namely <em>M. rotans</em> and <em>M. viridis</em>. We studied one population of <em>M. rotans</em>, using in vivo observation and silver carbonate and silver nitrate impregnation, and two populations of <em>M. viridis</em>, using in vivo observation, silver carbonate impregnation, and 18S rRNA gene sequencing. Phylogenetic analyses strongly support the position of <em>M. viridis</em> in the class Oligohymenophorea. Morphologic features suggest <em>Malacophrys rotans</em> belongs to order Tetrahymenida, but a confident phylogenetic assignment awaits its molecular sequencing. Differences between their oral structures and silverline patterns indicate that <em>M. rotans</em> and <em>M. viridis</em> likely belong to different genera. A formal separation at the genus level awaits molecular characterization of the type species, <em>M. rotans</em>.</div></div>","PeriodicalId":20781,"journal":{"name":"Protist","volume":"176 ","pages":"Article 126089"},"PeriodicalIF":1.9,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of the encystment-inducing activity of extracellular fluid from encysting vegetative cells in the terrestrial ciliated protozoa Colpoda cucullus","authors":"Yuto Shimada ,&nbsp;Arisa Momota ,&nbsp;Ayumu Onda ,&nbsp;Mikihiko Arikawa","doi":"10.1016/j.protis.2025.126088","DOIUrl":"10.1016/j.protis.2025.126088","url":null,"abstract":"<div><div>The terrestrial ciliated protozoan <em>Colpoda cucullus</em> transforms into a dehydration-resistant cyst upon sensing adverse signals. Recently, we identified a pheromone secreted by encysting vegetative cells of <em>C. cucullus</em>, termed “encystment-inducing pheromone” (EnIP), and characterized its properties. Overpopulated vegetative cells spontaneously encysted in ion-free ultrapure water without external stimuli. The external solution of encysting cells markedly induced encystment in vegetative cells under low cell density conditions, suggesting that EnIP, secreted by encysting cells into the external solution, induced encystment in vegetative cells. Further investigations revealed the following properties of EnIP: 1) EnIP retains encystment-inducing activity even in the presence of EGTA. 2) EnIP exhibits a concentration-dependent encystment effect. 3) EnIP is released within hours at high cell density. 4) EnIP is released by exocytosis. 5) EnIP loses its activity after 1–2 days. 6) EnIP is inactivated by heating and treatment with proteolytic enzymes. 7) The nominal molecular weight of EnIP was estimated to range between 10 and 100 kDa. These findings lead to the conclusion that encystment-induced <em>C. cucullus</em> vegetative cells secrete EnIP, a protein pheromone, with encystment-inducing activity for other cells. This study contributes to understanding microbial communication and reveals a novel mechanism for protist survival in harsh environments.</div></div>","PeriodicalId":20781,"journal":{"name":"Protist","volume":"176 ","pages":"Article 126088"},"PeriodicalIF":1.9,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143436443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The protist symbionts of Reticulitermes tibialis: Unexpected diversity enables a new taxonomic framework","authors":"Nicole L. Coots,&nbsp;Daniel E. Jasso-Selles,&nbsp;Kali L. Swichtenberg,&nbsp;Serena G. Aguilar,&nbsp;LeAnn Nguyen,&nbsp;Piper G. Sidles,&nbsp;Cindy Woo,&nbsp;Harrison M. Smith,&nbsp;Bailey J. Bresee,&nbsp;Amir A. Abboud,&nbsp;Tala Abd Al Rahman,&nbsp;Ritika Anand,&nbsp;Sergio R. Avalle,&nbsp;Anuvi Batra,&nbsp;Mackenzie A. Brown,&nbsp;Hilary Camacho Ruelas,&nbsp;Alfanarely Fajardo Chavez,&nbsp;Campbell N. Gallegos,&nbsp;Amalia Grambs,&nbsp;D. Armaan Hernández,&nbsp;Gillian H. Gile","doi":"10.1016/j.protis.2025.126087","DOIUrl":"10.1016/j.protis.2025.126087","url":null,"abstract":"<div><div>Wood-feeding termites harbor specialized protists in their hindguts in a classic nutritional mutualism. The protists are vertically inherited, which has generated a broad-scale pattern of codiversification over ∼150 million years, but there are many incongruences due to lineage-specific loss and transfer of symbionts. Despite the evolutionary and economic importance of this symbiosis, the symbiont communities of most termite species are incompletely characterized or entirely unstudied. Here, we have investigated the protist symbiont community of <em>Reticulitermes tibialis,</em> using single-cell PCR to link morphology to 18S rRNA gene sequences. The protists belong to at least 41 species in 3 major lineages within Metamonada: Spirotrichonymphida, Pyrsonymphidae, and <em>Trichonympha</em>. The Spirotrichonymphida symbionts belong to 6 genera, including <em>Pseudospironympha</em>, which has not been found in <em>Reticulitermes</em> until now, and <em>Dexiohelix</em>, a new genus. Pyrsonymphidae traditionally include just <em>Pyrsonympha</em> and <em>Dinenympha</em>, but our morphology-linked 18S phylogeny indicates that both genera are polyphyletic. We accordingly restrict the definitions of <em>Pyrsonympha</em> and <em>Dinenympha</em> to the clades that include their type species, and we propose 5 new genera to accommodate the remaining clades. Short-read 18S amplicon sequencing revealed considerable variation in community composition across <em>R. tibialis</em> colonies in Arizona, suggestive of a symbiont metacommunity. Symbiont species varied in their prevalence across colonies, with a core set of about 12 highly prevalent symbiont species, 11 species with intermediate prevalence, and 18 rare species. This pattern contrasts with the traditional paradigm of consistent symbiont community composition across colonies of a termite species.</div></div>","PeriodicalId":20781,"journal":{"name":"Protist","volume":"176 ","pages":"Article 126087"},"PeriodicalIF":1.9,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143372666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cytoplasmic streaming of symbiotic algae in the ciliate Stentor pyriformis","authors":"Hitoshi Iida","doi":"10.1016/j.protis.2025.126086","DOIUrl":"10.1016/j.protis.2025.126086","url":null,"abstract":"<div><div><em>Stentor pyriformis</em> is a unicellular organism whose inherent green-algal symbionts can be utilized in evolutionary and cytological studies. The cytoplasm contains symbiotic algae and starch granules, which are in constant motion. The habitats of the ciliate <em>S. pyriformis</em> are restricted to a few oligotrophic ponds in Japan. This study aimed to develop a culture medium for long-term incubation based on pond water quality data and to investigate the cytoplasmic streaming of symbiotic algae and starch granules in <em>S. pyriformis</em>. In addition, the involvement of the cytoskeleton and motor proteins in cytoplasmic streaming was examined using microtubule polymerization and dynein ATPase inhibitors. The results indicated that the cytoplasmic streaming in <em>S. pyriformis</em> is associated with the microtubule system. Immunofluorescence and transmission electron microscopy revealed the presence of KM-fibers, bundles of microtubules running longitudinally along the cell surface. These findings suggest a possible link between microtubules and cytoplasmic streaming in <em>S. pyriformis.</em></div></div>","PeriodicalId":20781,"journal":{"name":"Protist","volume":"176 ","pages":"Article 126086"},"PeriodicalIF":1.9,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143047707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Slowly evolving proteins support the monophyly of Craspedida (Choanoflagellatea) and a marine origin of choanoflagellates","authors":"Juan J. Ginés-Rivas,&nbsp;Martin Carr","doi":"10.1016/j.protis.2025.126085","DOIUrl":"10.1016/j.protis.2025.126085","url":null,"abstract":"<div><div>Choanoflagellate species have been taxonomically divided upon the morphological and developmental basis of their extracellular coat (periplast). Species within the order Craspedida possess a purely organic periplast, whereas taxa of the order Acanthoecida have an additional silica based periplast termed the lorica. Whilst small-scale phylogenetic studies have recovered the two orders as monophyletic, recent phylogenomic analyses have rejected the monophyly of the craspedids. These analyses suggest that the freshwater craspedid <em>Codosiga hollandica</em> falls within the earliest branching choanoflagellate lineage; however, it has also been noted that phylogenomic studies result in inconsistent phylogenies, with unstable long-branched species being recovered as basal choanoflagellates. Presented here are phylogenetic analyses, based upon slowly evolving ribosomal proteins, which consistently recover both craspedid monophyly and a derived placement of <em>C. hollandica</em>. The addition of further, long-branched, ribosomal proteins to phylogenetic analyses are shown to generate longer terminal branches and a weakening of the support for Craspedida. The analyses highlight the requirement for an increase in data, in terms of both taxa and gene coverage, to successfully resolve the earliest craspedid branches. In addition, phylogenetically unstable species are identified that are recommended to be omitted from phylogenomic studies as they have the potential to disrupt recovered relationships.</div></div>","PeriodicalId":20781,"journal":{"name":"Protist","volume":"176 ","pages":"Article 126085"},"PeriodicalIF":1.9,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143028971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular phylogeny, morphology, and ultrastructure of a Mesomycetozoea member, Sphaeroforma nootkatensis isolated from Pacific oyster, Crassostrea gigas, on the Southern coast of Korea","authors":"Seung-Hyeon Kim ,&nbsp;S.D.N.K. Bathige ,&nbsp;Donghyun Lee ,&nbsp;W.A.A.H. Kalhari ,&nbsp;Hyoun Joong Kim ,&nbsp;Kyung-Il Park","doi":"10.1016/j.protis.2024.126084","DOIUrl":"10.1016/j.protis.2024.126084","url":null,"abstract":"<div><div>This study discovered the first Asian population of <em>Sphaeroforma nootkatensis</em> (SphX), a member of Mesomycetozoea, in the southern coastal region of South Korea. Although investigating parasites in Pacific oysters (<em>Crassostrea gigas</em>), a single-cell microorganism was isolated from gill tissues. Comprehensive phylogenetic analysis of its 18S rDNA revealed its placement within the order Ichthyophonida, class Mesomycetozoea. SphX formed a distinct cluster within <em>Sphaeroforma</em> spp., separate from <em>Pseudoperkinsus tapetis</em>. Morphological examinations of in vitro cultured cells revealed two distinctive life stages characterized by multilobe and granular sporangium, accompanied by corresponding non-motile larger and motile smaller endospores, respectively. Scanning electron microscope analysis depicted lobular and smooth surfaces on vegetative cells, indicative of differing life cycle stages. Transmission electron microscope observations revealed intriguing features consistent with previous reports on Mesomycetozoea. A prominent fibrillar structure was noted in a vegetative cell. In contrast, smaller endospores were observed with cilia-like structures surrounding the cell wall, indicating their mode of movement. The Ray's fluid thioglycollate medium assay showed that SphX cells were digested, whereas some small endospores remained resistant. This discovery provides novel insights into the life stages of Mesomycetozoans and geographical distribution and underscores the importance of monitoring oyster health for effective aquaculture management.</div></div>","PeriodicalId":20781,"journal":{"name":"Protist","volume":"176 ","pages":"Article 126084"},"PeriodicalIF":1.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142915088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Environmental interactions between protists and bacterial communities in hydrocarbon degradation","authors":"Komal A. Chandarana,&nbsp;Sapna Chandwani,&nbsp;Harshida A. Gamit,&nbsp;Hetvi Naik,&nbsp;Natarajan Amaresan","doi":"10.1016/j.protis.2024.126083","DOIUrl":"10.1016/j.protis.2024.126083","url":null,"abstract":"<div><div>Reclamation of petroleum-polluted environments is a key issue for today and in the future, as our reliance on oil will persist for decades. An eco-friendly solution is to use microbes that play a role in petroleum-hydrocarbon degradation. However, as hydrocarbon degradation involves a multi-step process involving different functional groups, focusing only on finding efficient bacterial species will not be the complete solution. Heterotrophic protists are unicellular eukaryotic microorganisms that could play a role in remediation of ecosystems by enhancing petroleum-hydrocarbon degradation through different mechanisms. This mini-review discusses the importance of protists in the degradation of petroleum-hydrocarbon and their predatory impact on hydrocarbon-degrading bacterial communities. Additionally, the effect of hydrocarbons on protistan community structure and protistan cells is discussed. A better understanding of the puzzle hydrocarbon-protist interactions will significantly increase our knowledge of how to employ these microbes for bioremediation of hydrocarbon pollutants.</div></div>","PeriodicalId":20781,"journal":{"name":"Protist","volume":"176 ","pages":"Article 126083"},"PeriodicalIF":1.9,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142872800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative chloroplast genome analysis of two Desmodesmus species reveals genome diversity within Scenedesmaceae (Sphaeropleales, Chlorophyceae)","authors":"Yan Xu ,&nbsp;Xiayi Chen ,&nbsp;Michael Melkonian ,&nbsp;Sibo Wang ,&nbsp;Sunil Kumar Sahu","doi":"10.1016/j.protis.2024.126073","DOIUrl":"10.1016/j.protis.2024.126073","url":null,"abstract":"<div><div><em>Desmodesmus</em> (Sphaeropleales, Chlorophyceae) is a genus of freshwater green algae widely distributed in aquatic ecosystems and known for its potential in biotechnology and bioremediation. We present the complete chloroplast genome sequences of two <em>Desmodesmus</em> species, <em>D. hystrix</em> and <em>D. perforatus</em>. Comparative analysis revealed significant differences in their quadripartite structures, particularly in the lengths of the small single copy regions. We observed variations in G + C content across genomic regions, with inverted repeat regions showing a higher G + C content. Microsatellite analysis revealed that A/T mononucleotides were the most abundant type, while dispersed repeat analysis suggested a potential link to expansion of the single-copy region in <em>D. perforatus</em>. Gene annotation, codon usage analysis, and comparison of genome rearrangement highlighted both similarities and differences between the species. Nucleotide diversity analysis revealed higher variability in intergenic regions than in coding regions, with IR regions displaying relative conservation. Comparative analyses of genomes and IR border arrangements demonstrated that the <em>Desmodesmus</em> species exhibit substantial differences in genome structure and gene arrangement among Scenedesmaceae. Phylogenetic analysis, based on 51 single-copy genes from 34 species of Sphaeropleales provided additional information about phylogenetic relationships within Sphaeropleales. These findings contribute to our understanding of comparative plastid genomics in green algae.</div></div>","PeriodicalId":20781,"journal":{"name":"Protist","volume":"175 6","pages":"Article 126073"},"PeriodicalIF":1.9,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142747697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New and noteworthy chrysophycean stomatocysts from the Steppe zone of South Urals (Russia) with comments on the morphological variability","authors":"Marina Ignatenko ,&nbsp;Tatyana Yatsenko-Stepanova ,&nbsp;Dmitry Kapustin","doi":"10.1016/j.protis.2024.126075","DOIUrl":"10.1016/j.protis.2024.126075","url":null,"abstract":"<div><div>Morphology of seven chrysophycean stomatocysts was studied using scanning electron microscopy. All stomatocysts were recorded from the shallow lakes located in the Steppe zone of South Urals. Four morphotypes (stomatocyst 373 Taylor et Smol, stomatocyst 68 Van de Vijver et Beyens, stomatocyst 99 Pang et Wang and stomatocyst 101 Pang et Wang <em>Forma B</em>) are rare and reported for the first time in Russia. New observations on the formation of the cyst ornamentation allowed us to amend the descriptions of two morphotypes. Three stomatocysts are described as new to science. Morphological variability of all seven morphotypes are illustrated and discussed.</div></div>","PeriodicalId":20781,"journal":{"name":"Protist","volume":"176 ","pages":"Article 126075"},"PeriodicalIF":1.9,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142771610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Protists and Society: A report on the 2024 autumn meeting of Protistology-UK, at the natural history museum, London","authors":"David J.S. Montagnes","doi":"10.1016/j.protis.2024.126072","DOIUrl":"10.1016/j.protis.2024.126072","url":null,"abstract":"","PeriodicalId":20781,"journal":{"name":"Protist","volume":"176 ","pages":"Article 126072"},"PeriodicalIF":1.9,"publicationDate":"2024-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142756628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}