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Diversity
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Integrated Taxonomy of Protists: Morphology, Genes and Symbionts
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Integrated Taxonomy of Protists: Morphology, Genes and Symbionts

A special issue of Diversity (ISSN 1424-2818). This special issue belongs to the section "Phylogeny and Evolution".

Deadline for manuscript submissions: closed (15 July 2023) | Viewed by 10728

Special Issue Editors

Dr. Martina Schrallhammer

E-Mail Website
Guest Editor
Department of Biology, Albert-Ludwigs Universität Freiburg, Freiburg im Breisgau, Germany
Interests: prokaryotic and eukaryotic symbionts of ciliates; microbial ecology; adaptation; evolution; intracellular bacteria; Paramecium; Rickettsia; Holospora; Caedibacter; Megaira
Special Issues, Collections and Topics in MDPI journals
Dr. Alexey Potekhin

E-Mail Website
Guest Editor
Research Department for Limnology, Mondsee, University of Innsbruck, A-5310 Mondsee, Austria
Interests: ciliates; Parameciu; protists; symbiosis; bacterial symbionts; microbiomes; mating types; speciation mechanisms; the species concept
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We would like to invite you to contribute to this Special Issue of Diversity, entitled “Integrated Taxonomy of Protists: Morphology, Genes, and Symbionts”. Protists, unicellular eukaryotes, are an extremely broad group of organisms revealing the vast diversity of life on our planet. The taxonomy and systematics of protists are, probably, among the most discussed and quickly evolving fields in biology. The species concept in protistology is very complex, and there are no straightforward approaches to solving the numerous problems of taxonomy for different groups of protists. Nowadays, taxonomy cannot be based only on a comparison of the morphology of organisms, neither it is sufficient to establish new taxa only from sequences of marker genes. Modern taxonomy integrates morphological, ultrastructural, and molecular phylogenetic analyses, and also benefits from genomic data. Another way to upgrade the taxonomic sciences would, probably, be the characterization of symbiotic systems. Nowadays, it is broadly accepted that all organisms have symbionts, whether obligatory or occasional. The impact of specific symbionts or microbial consortia (i.e., microbiomes) on the morphology, physiology, development, and ecology of the hosts sometimes may define the specificity and uniqueness of the organisms and drive their evolution. Protists host a great variety of eukaryotic and prokaryotic symbionts, and such associations between unicellular organisms are highly fine-tuned and adaptive. Methodological improvements may facilitate a better understanding of host–symbiont interactions, thus helping us to elucidate basic concepts of Life.

This Special Issue aims to highlight the studies that address the diversity of protists from ecologically peculiar habitats, provide integrative characterization of protist species, or describe symbiotic associations in which protists are involved.

Dr. Martina Schrallhammer
Dr. Alexey Potekhin
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Diversity is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (6 papers)

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Research

20 pages, 10480 KiB  
Article
Phenotypic Polymorphism in Two Endosymbiotic Bacteria of the Ciliate Paramecium: Pseudolyticum multiflagellatum and “Ca. Megaira venefica”
by Ekaterina Kursacheva, Alexander Korotaev, Konstantin Benken, Natalia Lebedeva and Elena Sabaneyeva
Diversity 2023, 15(8), 924; https://doi.org/10.3390/d15080924 - 11 Aug 2023
Viewed by 1017
Abstract
Here, we report a comprehensive description of the stable associations between two Paramecium species (P. nephridiatum and P. caudatum) and their cytoplasmic bacterial endosymbiont Pseudolyticum multiflagellatum. These spindle-like, rod-shaped, non-motile peritrichous bacteria demonstrate significant phenotypic polymorphism. Considering the differences in [...] Read more.
Here, we report a comprehensive description of the stable associations between two Paramecium species (P. nephridiatum and P. caudatum) and their cytoplasmic bacterial endosymbiont Pseudolyticum multiflagellatum. These spindle-like, rod-shaped, non-motile peritrichous bacteria demonstrate significant phenotypic polymorphism. Considering the differences in bacterial morphology and host species, several scientific groups have previously described these endosymbionts as distinct species. Our study provides brand-new molecular data, which allows us to unify earlier descriptions and determine the phylogenetic position of this endosymbiont as a member of the family “Ca. Midichloriaceae” (Rickettsiales). The distinguishing feature of this bacterium is the presence of a highly refractive granule in its cytoplasm, well detectable with differential interference contrast (DIC) microscopy. The protein nature of these peculiar inclusion bodies is considered. The other endosymbiont, “Ca. Megaira venefica”, co-inhabiting the cytoplasm of the studied P. nephridiatum strains, also displayed polymorphism, rounded forms being infected with phages. Full article
(This article belongs to the Special Issue Integrated Taxonomy of Protists: Morphology, Genes and Symbionts)
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19 pages, 10194 KiB  
Article
Morphological and Phylogenetic Study of Protococcidians Sheds Light on the Evolution of Epicellular Parasitism in Sporozoa (Apicomplexa), with the Description of Eleutheroschizon planoratum sp. nov
by Gita G. Paskerova, Tatiana S. Miroliubova, Andrea Valigurová, Vladimir V. Aleoshin and Timur G. Simdyanov
Diversity 2023, 15(7), 863; https://doi.org/10.3390/d15070863 - 17 Jul 2023
Cited by 1 | Viewed by 1048
Abstract
The order Protococcidiida is one of the most poorly studied basal groups of Sporozoa (Apicomplexa sensu stricto). To date, the phylogenetic unity of protococcidians and their relationship with other sporozoans are understudied. Only the protococcidian Eleutheroschizon duboscqi has molecular evidence of a sister [...] Read more.
The order Protococcidiida is one of the most poorly studied basal groups of Sporozoa (Apicomplexa sensu stricto). To date, the phylogenetic unity of protococcidians and their relationship with other sporozoans are understudied. Only the protococcidian Eleutheroschizon duboscqi has molecular evidence of a sister position to “true” coccidians (Eimeria, Sarcocystis, Toxoplasma). E. duboscqi is characterized by epicellular development in the so-called parasitophorous sac of the host cell origin. The unusual localization of Eleutheroschizon is comparable to that of Cryptosporidium. We describe a new species of the genus, E. planoratum ex Naineris quadricuspida polychaete from the White Sea, using light and electron microscopy. The morphology of attachment apparatus, phylogenetic analyses of concatenated DNA sequences of the nuclear ribosomal operon (SSU rDNA, ITS1, 5.8S rDNA, ITS2, and LSU rDNA), and compensatory base changes in ITS2 secondary structures of both protococcidians confirm the new species. The resulting phylogenies also confirm that Eleutheroschizon is sister to eimeriid coccidians, while Cryptosporidium tends to be grouped with gregarines. We discuss a new type of endoparasitism among sporozoans—the closed epicellular parasitism that evolved convergently in Eleutheroschizon and Cryptosporidium. The diagnosis of the new species and the emended diagnoses of the species E. duboscqi and the genus Eleutheroschizon are presented. Full article
(This article belongs to the Special Issue Integrated Taxonomy of Protists: Morphology, Genes and Symbionts)
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14 pages, 4061 KiB  
Article
Characterization of a Pseudokeronopsis Strain (Ciliophora, Urostylida) and Its Bacterial Endosymbiont “Candidatus Trichorickettsia” (Alphaproteobacteria, Rickettsiales)
by Michele Castelli, Valentina Serra, Leandro Gammuto, Marcus V. X. Senra, Letizia Modeo and Giulio Petroni
Diversity 2022, 14(12), 1032; https://doi.org/10.3390/d14121032 - 25 Nov 2022
Viewed by 1497
Abstract
Symbiotic associations between bacteria and ciliate protists are rather common. In particular, several cases were reported involving bacteria of the alphaproteobacterial lineage Rickettsiales, but the diversity, features, and interactions in these associations are still poorly understood. In this work, we characterized a [...] Read more.
Symbiotic associations between bacteria and ciliate protists are rather common. In particular, several cases were reported involving bacteria of the alphaproteobacterial lineage Rickettsiales, but the diversity, features, and interactions in these associations are still poorly understood. In this work, we characterized a novel ciliate protist strain originating from Brazil and its associated Rickettsiales endosymbiont by means of live and ultrastructural observations, as well as molecular phylogeny. Though with few morphological peculiarities, the ciliate was found to be phylogenetically affiliated with Pseudokeronopsis erythrina, a euryhaline species, which is consistent with its origin from a lagoon with significant spatial and seasonal salinity variations. The bacterial symbiont was assigned to “Candidatus Trichorickettsia mobilis subsp. hyperinfectiva”, being the first documented case of a Rickettsiales associated with urostylid ciliates. It resided in the host cytoplasm and bore flagella, similarly to many, but not all, conspecifics in other host species. These findings highlight the ability of “Candidatus Trichorickettsia” to infect multiple distinct host species and underline the importance of further studies on this system, in particular on flagella and their regulation, from a functional and also an evolutionary perspective, considering the phylogenetic proximity with the well-studied and non-flagellated Rickettsia. Full article
(This article belongs to the Special Issue Integrated Taxonomy of Protists: Morphology, Genes and Symbionts)
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15 pages, 9867 KiB  
Article
Widespread Occurrence of Two Planktonic Ciliate Species (Urotricha, Prostomatida) Originating from High Mountain Lakes
by Bettina Sonntag, Daniela Frantal, Barbara Kammerlander, Tatyana Darienko, Sabine Filker, Thorsten Stoeck, Michael Gruber and Thomas Pröschold
Diversity 2022, 14(5), 362; https://doi.org/10.3390/d14050362 - 04 May 2022
Cited by 4 | Viewed by 2059
Abstract
Ciliates of the genus Urotricha are widely distributed and occur in almost any freshwater body. Thus far, almost all species have been described from morphology only. Here, we applied an integrative approach on the morphology, molecular phylogeny and biogeography of two species isolated [...] Read more.
Ciliates of the genus Urotricha are widely distributed and occur in almost any freshwater body. Thus far, almost all species have been described from morphology only. Here, we applied an integrative approach on the morphology, molecular phylogeny and biogeography of two species isolated from high mountain lakes in the Central Alps, Austria. As these remote lakes are known to have water temperatures <15 °C, our hypothesis was that these urotrichs might prefer ‘cold’ environments. We studied the morphological details from living and silver-stained individuals, and their molecular sequences (ribosomal operon, ITS), and screened available datasets for their biogeography. The two Urotricha species resembled morphological features of several congeners. An accurate species assignment was difficult due to several overlapping characteristics. However, we tentatively attributed the investigated species to Urotricha nais and Urotricha globosa. The biogeographic analyses revealed their occurrence in Europe, Africa and Asia, and no correlations to (cold) temperatures were found. Our findings suggest that these two urotrichs, originating from two cold and remote habitats, are probably cryptic species well adapted to their harsh environment. Full article
(This article belongs to the Special Issue Integrated Taxonomy of Protists: Morphology, Genes and Symbionts)
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19 pages, 2782 KiB  
Article
Ecological Study of the Active Ciliate Community from Bromeliads during the Humid Season in Different Types of Forests of the Mexican Neotropics
by Carlos Alberto Durán-Ramírez and Rosaura Mayén-Estrada
Diversity 2022, 14(2), 122; https://doi.org/10.3390/d14020122 - 08 Feb 2022
Cited by 2 | Viewed by 1423
Abstract
Bromeliads are a Neotropical family of monocots, colonized by several families of ciliates, with some species that inhabit only this type of microecosystems. Ecological factors such as the presence of water, plant volume, seasonality and predators, have been recognized as important factors, which [...] Read more.
Bromeliads are a Neotropical family of monocots, colonized by several families of ciliates, with some species that inhabit only this type of microecosystems. Ecological factors such as the presence of water, plant volume, seasonality and predators, have been recognized as important factors, which play a role in the ciliate community structure in tank bromeliads. The objective of this study is to describe different communities of active ciliates from epiphytic and terrestrial bromeliads that inhabit the dry tropical forest, montane cloud forest, oak forest and semideciduous tropical forest in the Mexican Neotropics during the humid season of the year 2016. We found 22 species of active ciliates. A higher richness of ciliate species was found in the bromeliads of the montane cloud forest. Based on statistical tests, we determine that the pH and water temperature, plant diameter, its distance above the ground and altitude above sea level in relation to ciliate abundance explain <50% of the variation; however, the combination of plant diameter and its distance above the ground shows a positive effect in relation to ciliate abundance. We provide new evidence that bromeliads that inhabit mountains and lowland forests in a larger geographic area host ciliate communities with different species composition. Full article
(This article belongs to the Special Issue Integrated Taxonomy of Protists: Morphology, Genes and Symbionts)
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8 pages, 1607 KiB  
Article
Effect of Cothurnia variabilis and Epistylis gammari (Ciliophora: Peritrichia) on Metabolic Rate of the Crayfish Cambarellus (Cambarellus) montezumae
by Mireya Ramírez-Ballesteros, René Cárdenas-Vázquez, Alfonso Lugo-Vázquez and Rosaura Mayén-Estrada
Diversity 2021, 13(7), 333; https://doi.org/10.3390/d13070333 - 19 Jul 2021
Cited by 1 | Viewed by 2259
Abstract
Peritrichs usually settle on the external surface and gills of crustaceans. However, their physiological effect on the host has not been studied. Respiratory rate is a susceptible index for some factors that affect an organism. To test if ciliates attached to the crustacean [...] Read more.
Peritrichs usually settle on the external surface and gills of crustaceans. However, their physiological effect on the host has not been studied. Respiratory rate is a susceptible index for some factors that affect an organism. To test if ciliates attached to the crustacean gills have a physiological effect, we measured crustacean oxygen consumption in a closed system. Crayfish Cambarellus (Cambarellus) montezumae were collected in Lago Xochimilco in Mexico City and were isolated in chambers. Two peritrich species, Cothurnia variabilis (32.5%) and Epistylis gammari (67.5%), were observed on the gills. The metabolic rate was evaluated by oxygen consumption with a polarimetric oximeter. Statistical analyses demonstrated that a density of ciliates attached to the gills of the crayfish above ~50 individuals increased oxygen consumption with a positive correlation to epibiont density. We conclude that C. variabilis and E. gammari ciliate epibionts attached to the gill of the crayfish Cambarellus (Cambarellus) montezumae cause an increase in metabolic rate. Full article
(This article belongs to the Special Issue Integrated Taxonomy of Protists: Morphology, Genes and Symbionts)
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