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Boscaro V, Syberg-Olsen MJ, Irwin NAT, George EE, Vannini C, Husnik F, Keeling PJ. All essential endosymbionts of the ciliate Euplotes are cyclically replaced. Curr Biol 2022; 32:R826-R827. [PMID: 35839761 DOI: 10.1016/j.cub.2022.06.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Symbiotic systems vary in the degree to which the partners are bound to each other1. At one extreme, there are intracellular endosymbionts in mutually obligate relationships with their host, often interpreted as mutualistic. The symbiosis between the betaproteobacterium Polynucleobacter and the ciliate Euplotes (clade B) challenges this view2: although freshwater Euplotes species long ago became dependent on endosymbionts, the many extant Polynucleobacter lineages they harbour arose recently and in parallel from different free-living ancestors2. The host requires the endosymbionts for reproduction and survival3, but each newly established symbiont is ultimately driven to extinction in a cycle of establishment, degeneration, and replacement. Similar replacement events have been observed in sap-feeding insects4-6, a model for bacteria-eukaryote symbioses7, but usually only affect a small subset of the host populations. Most insects retain an ancient coevolving symbiont, suggesting that long-term mutualism and permanent integration remains the rule and symbiont turnovers are mere evolutionary side-stories. Here we show that this is not the case for Euplotes. We examined all known essential Euplotes symbionts and found that none are ancient or coevolving; rather, all are recently established and continuously replaced over relatively short evolutionary time spans, making the symbiosis ancient for the host but not for any bacterial lineage.
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Affiliation(s)
- Vittorio Boscaro
- University of British Columbia, Department of Botany, Vancouver, BC, V6T 1Z4, Canada.
| | | | - Nicholas A T Irwin
- University of British Columbia, Department of Botany, Vancouver, BC, V6T 1Z4, Canada; University of Oxford, Merton College, Oxford, OX1 4JD, UK
| | - Emma E George
- University of British Columbia, Department of Botany, Vancouver, BC, V6T 1Z4, Canada
| | - Claudia Vannini
- Department of Biology, University of Pisa, Pisa, 56126, Italy
| | - Filip Husnik
- University of British Columbia, Department of Botany, Vancouver, BC, V6T 1Z4, Canada; Okinawa Institute of Science and Technology, Okinawa, 904-0495, Japan
| | - Patrick J Keeling
- University of British Columbia, Department of Botany, Vancouver, BC, V6T 1Z4, Canada
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Abstract
Prokaryotic genomes are usually densely packed with intact and functional genes. However, in certain contexts, such as after recent ecological shifts or extreme population bottlenecks, broken and nonfunctional gene fragments can quickly accumulate and form a substantial fraction of the genome. Identification of these broken genes, called pseudogenes, is a critical step for understanding the evolutionary forces acting upon, and the functional potential encoded within, prokaryotic genomes. Here, we present Pseudofinder, an open-source software dedicated to pseudogene identification and analysis in bacterial and archaeal genomes. We demonstrate that Pseudofinder’s multi-pronged, reference-based approach can detect a wide variety of pseudogenes, including those that are highly degraded and typically missed by gene-calling pipelines, as well newly formed pseudogenes containing only one or a few inactivating mutations. Additionally, Pseudofinder can detect genes that lack inactivating substitutions but experiencing relaxed selection. Implementation of Pseudofinder in annotation pipelines will allow more precise estimations of the functional potential of sequenced microbes, while also generating new hypotheses related to the evolutionary dynamics of bacterial and archaeal genomes.
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Affiliation(s)
| | - Arkadiy I Garber
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
| | - Patrick J Keeling
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - John P McCutcheon
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA.,Howard Hughes Medical Institute, 4000 Jones Bridge Road, Chevy Chase, Maryland, USA
| | - Filip Husnik
- Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada.,Okinawa Institute of Science and Technology, Okinawa, Japan
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Boscaro V, Syberg-Olsen MJ, Irwin NAT, del Campo J, Keeling PJ. What Can Environmental Sequences Tell Us About the Distribution of Low-Rank Taxa? The Case of Euplotes
(Ciliophora, Spirotrichea), Including a Description of Euplotes enigma
sp. nov. J Eukaryot Microbiol 2018; 66:281-293. [DOI: 10.1111/jeu.12669] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 07/11/2018] [Accepted: 07/14/2018] [Indexed: 02/06/2023]
Affiliation(s)
- Vittorio Boscaro
- Department of Botany; University of British Columbia; 3529-6270 University Boulevard Vancouver British Columbia V6T1Z4 Canada
| | - Mitchell J. Syberg-Olsen
- Department of Botany; University of British Columbia; 3529-6270 University Boulevard Vancouver British Columbia V6T1Z4 Canada
| | - Nicholas A. T. Irwin
- Department of Botany; University of British Columbia; 3529-6270 University Boulevard Vancouver British Columbia V6T1Z4 Canada
| | - Javier del Campo
- Department of Botany; University of British Columbia; 3529-6270 University Boulevard Vancouver British Columbia V6T1Z4 Canada
- Department of Marine Biology and Oceanography; Institut de Ciències del Mar - CSIC; Passeig Marítim de la Barceloneta, 37-49 08003 Barcelona Catalonia Spain
| | - Patrick J. Keeling
- Department of Botany; University of British Columbia; 3529-6270 University Boulevard Vancouver British Columbia V6T1Z4 Canada
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Boscaro V, Santoferrara LF, Zhang Q, Gentekaki E, Syberg-Olsen MJ, Del Campo J, Keeling PJ. EukRef-Ciliophora: a manually curated, phylogeny-based database of small subunit rRNA gene sequences of ciliates. Environ Microbiol 2018; 20:2218-2230. [PMID: 29727060 DOI: 10.1111/1462-2920.14264] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 04/13/2018] [Accepted: 04/27/2018] [Indexed: 01/01/2023]
Abstract
High-throughput sequencing (HTS) surveys, among the most common approaches currently used in environmental microbiology, require reliable reference databases to be correctly interpreted. The EukRef Initiative (eukref.org) is a community effort to manually screen available small subunit (SSU) rRNA gene sequences and produce a public, high-quality and informative framework of phylogeny-based taxonomic annotations. In the context of EukRef, we present a database for the monophyletic phylum Ciliophora, one of the most complex, diverse and ubiquitous protist groups. We retrieved more than 11 500 sequences of ciliates present in GenBank (28% from identified isolates and 72% from environmental surveys). Our approach included the inference of phylogenetic trees for every ciliate lineage and produced the largest SSU rRNA tree of the phylum Ciliophora to date. We flagged approximately 750 chimeric or low-quality sequences, improved the classification of 70% of GenBank entries and enriched environmental and literature metadata by 30%. The performance of EukRef-Ciliophora is superior to the current SILVA database in classifying HTS reads from a global marine survey. Comprehensive outputs are publicly available to make the new tool a useful guide for non-specialists and a quick reference for experts.
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Affiliation(s)
- Vittorio Boscaro
- Department of Botany, University of British Columbia, Vancouver, BC, Canada
| | - Luciana F Santoferrara
- Department of Marine Sciences, University of Connecticut, Stamford, CT, USA.,Department of Ecology and Evolutionary Biology, University of Connecticut, Stamford, CT, USA
| | - Qianqian Zhang
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China
| | - Eleni Gentekaki
- School of Science, Mae Fah Luang University, Chiang Rai, Thailand
| | | | - Javier Del Campo
- Department of Botany, University of British Columbia, Vancouver, BC, Canada
| | - Patrick J Keeling
- Department of Botany, University of British Columbia, Vancouver, BC, Canada
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Syberg-Olsen MJ, Irwin NAT, Vannini C, Erra F, Di Giuseppe G, Boscaro V, Keeling PJ. Biogeography and Character Evolution of the Ciliate Genus Euplotes (Spirotrichea, Euplotia), with Description of Euplotes curdsi sp. nov. PLoS One 2016; 11:e0165442. [PMID: 27828996 PMCID: PMC5102374 DOI: 10.1371/journal.pone.0165442] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Accepted: 10/06/2016] [Indexed: 01/08/2023] Open
Abstract
Ciliates comprise a diverse and ecologically important phylum of unicellular protists. One of the most specious and best-defined genera is Euplotes, which constitutes more than 70 morphospecies, many of which have never been molecularly tested. The increasing number of described Euplotes taxa emphasizes the importance for detailed characterizations of new ones, requiring standardized morphological observations, sequencing of molecular markers and careful comparison with previous literature. Here we describe Euplotes curdsi sp. nov., distinguishable by the combination of the following features: 45–65 μm length, oval or elongated shape with both ends rounded, narrow peristome with 25–34 adoral membranelles, conspicuous paroral membrane, double-eurystomus dorsal argyrome type, 6–7 dorsolateral kineties and 10 frontoventral cirri. Three populations of the novel species have been found in brackish and marine samples in the Mediterranean and the White Sea. We provide the SSU rRNA gene sequences of these populations, and an updated phylogeny of the genus Euplotes. Using the molecular phylogenetic tree, we inferred aspects of the biogeographical history of the genus and the evolution of its most important taxonomic characters in order to provide a frame for future descriptions. Ultimately, these data reveal recurrent trends of freshwater invasion and highlight the dynamic, yet convergent, morphological evolution of Euplotes.
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Affiliation(s)
- Mitchell J. Syberg-Olsen
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | - Nicholas A. T. Irwin
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Fabrizio Erra
- Dipartimento di Biologia, Università di Pisa, Pisa, Italy
| | | | - Vittorio Boscaro
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
| | - Patrick J. Keeling
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada
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