{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,18]],"date-time":"2026-10-18T05:10:58Z","timestamp":1792300258970,"version":"4.4.0"},"reference-count":50,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,2,1]],"date-time":"2026-02-01T00:00:00Z","timestamp":1769904000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000038","name":"Natural Sciences and Engineering Research Council of Canada","doi-asserted-by":"crossref","award":["RGPIN-2022-03066"],"award-info":[{"award-number":["RGPIN-2022-03066"]}],"id":[{"id":"10.13039\/501100000038","id-type":"DOI","asserted-by":"crossref"}]},{"name":"NSERC Undergraduate Student Research Award"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>The previous discovery of genomes of Polinton-like viruses (PLVs) associated with viruses of Chrysochromulina parva stimulated this research to determine the biological nature of these putative viral hyperparasites. Purification of C. parva viruses to enable co-infection experiments led to the discovery of a previously unknown virus, CpV-BQ3, which, based on sequence information and electron microscopy, is a species of Tethysvirus, a genus within the Megaviricetes. Purification and TEM imaging of CpV-PLV Moe revealed naked icosahedral particles morphologically similar to other cultivated virophages and PLVs. Mixed-infection experiments with the putative Polinton-like virus CpV-PLV Moe demonstrated that CpV-BQ3 supports its replication, whereas the putative Phycodnavirus CpV-BQ1 does not. Further, experimental infections with differing proportions of the Moe and its helper virus CpV-BQ3 revealed a dose-effect whereby high levels of Moe had a greater negative impact on BQ3 replication compared to lower levels. Conversely, high levels of Moe relative to BQ3 provided greater protection for C. parva, allowing enhanced cell survival, whereas low doses of Moe did not prevent cell lysis. Overall, the results of this study demonstrated the intimate relationship of CpV-PLV Moe with the newly discovered virus, CpV-BQ3, and C. parva, and illustrate the complex ecology of algal viruses.<\/jats:p>","DOI":"10.3390\/v18020196","type":"journal-article","created":{"date-parts":[[2026,2,2]],"date-time":"2026-02-02T12:00:47Z","timestamp":1770033647000},"page":"196","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["A Polinton-like Virus of C. parva Inhibits the Population Growth of a Newly Isolated Relative of Tethysvirus ontarioense"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-2821-5304","authenticated-orcid":false,"given":"George R.","family":"Thomas","sequence":"first","affiliation":[{"name":"Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ichiro","family":"Inamoto","sequence":"additional","affiliation":[{"name":"Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3037-0064","authenticated-orcid":false,"given":"Christine N.","family":"Palermo","sequence":"additional","affiliation":[{"name":"Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gurshan","family":"Bajaj","sequence":"additional","affiliation":[{"name":"Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6576-4883","authenticated-orcid":false,"given":"Steven M.","family":"Short","sequence":"additional","affiliation":[{"name":"Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"100","DOI":"10.1038\/nature07218","article-title":"The virophage as a unique parasite of the giant mimivirus","volume":"455","author":"Desnues","year":"2008","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"231","DOI":"10.1126\/science.1199412","article-title":"A virophage at the origin of large DNA transposons","volume":"332","author":"Fischer","year":"2011","journal-title":"Science"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"6163","DOI":"10.1073\/pnas.1018221108","article-title":"Virophage control of Antarctic algal host-virus dynamics","volume":"108","author":"Yau","year":"2011","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Wu, Z.Q., Chu, T., Sheng, Y.J., Yu, Y.X., and Wang, Y.J. (2023). Diversity, relationship, and distribution of virophages and large algal viruses in global ocean viromes. Viruses, 15.","DOI":"10.3390\/v15071582"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Yutin, N., Shevchenko, S., Kapitonov, V., Krupovic, M., and Koonin, E.V. (2015). A novel group of diverse Polinton-like viruses discovered by metagenome analysis. BMC Biol., 13.","DOI":"10.1186\/s12915-015-0207-4"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"e00149-20","DOI":"10.1128\/JVI.00149-20","article-title":"Novel cell-virus-virophage tripartite infection systems discovered in the freshwater Lake Dishui Lake in Shanghai, China","volume":"94","author":"Xu","year":"2020","journal-title":"J. Virol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1278","DOI":"10.1128\/JVI.03039-14","article-title":"Three novel virophage genomes discovered from Yellowstone Lake metagenomes","volume":"89","author":"Zhou","year":"2015","journal-title":"J. Virol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"4225","DOI":"10.1128\/JVI.03398-12","article-title":"Diversity of virophages in metagenomic data sets","volume":"87","author":"Zhou","year":"2013","journal-title":"J. Virol."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Gaia, M., Benamar, S., Boughalmi, M., Pagnier, I., Croce, O., Colson, P., Raoult, D., and La Scola, B. (2014). Zamilon, a novel virophage with mimiviridae host specificity. PLoS ONE, 9.","DOI":"10.1371\/journal.pone.0094923"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"762","DOI":"10.1038\/nrmicro2676","article-title":"Virophages or satellite viruses?","volume":"9","author":"Krupovic","year":"2011","journal-title":"Nat. Rev. Microbiol."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Mougari, S., Sahmi-Bounsiar, D., Levasseur, A., Colson, P., and La Scola, B. (2019). Virophages of giant viruses: An update at eleven. Viruses, 11.","DOI":"10.3390\/v11080733"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"233","DOI":"10.1007\/s00705-015-2622-9","article-title":"A classification system for virophages and satellite viruses","volume":"161","author":"Krupovic","year":"2016","journal-title":"Arch. Virol."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Roux, S., Fischer, M.G., Hackl, T., Katz, L.A., Schulz, F., and Yutin, N. (2023). Updated virophage taxonomy and distinction from polinton-like viruses. Biomolecules, 13.","DOI":"10.3390\/biom13020204"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1016\/j.coviro.2017.06.008","article-title":"Polintons, virophages and transpovirons: A tangled web linking viruses, transposons and immunity","volume":"25","author":"Koonin","year":"2017","journal-title":"Curr. Opin. Virol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1038\/nrmicro3389","article-title":"Polintons: A hotbed of eukaryotic virus, transposon and plasmid evolution","volume":"13","author":"Krupovic","year":"2015","journal-title":"Nat. Rev. Microbiol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"158","DOI":"10.1186\/1743-422X-10-158","article-title":"Virophages, polintons, and transpovirons: A complex evolutionary network of diverse selfish genetic elements with different reproduction strategies","volume":"10","author":"Yutin","year":"2013","journal-title":"Virol. J."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"D708","DOI":"10.1093\/nar\/gkx932","article-title":"Virus taxonomy: The database of the International Committee on Taxonomy of Viruses (ICTV)","volume":"46","author":"Lefkowitz","year":"2018","journal-title":"Nucleic Acids Res."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"e0008623","DOI":"10.1128\/mmbr.00086-23","article-title":"The polinton-like supergroup of viruses: Evolution, molecular biology, and taxonomy","volume":"88","author":"Koonin","year":"2024","journal-title":"Microbiol. Mol. Biol. Rev."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"6","DOI":"10.1186\/1745-6150-9-6","article-title":"Conservation of major and minor jelly-roll capsid proteins in Polinton (Maverick) transposons suggests that they are bona fide viruses","volume":"9","author":"Krupovic","year":"2014","journal-title":"Biol. Direct"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"10800","DOI":"10.1073\/pnas.1303251110","article-title":"Genome of Phaeocystis globosa virus PgV-16T highlights the common ancestry of the largest known DNA viruses infecting eukaryotes","volume":"110","author":"Santini","year":"2013","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1186\/s40168-020-00956-0","article-title":"Polinton-like viruses are abundant in aquatic ecosystems","volume":"9","author":"Bellas","year":"2021","journal-title":"Microbiome"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"e2300465120","DOI":"10.1073\/pnas.2300465120","article-title":"Large-scale invasion of unicellular eukaryotic genomes by integrating DNA viruses","volume":"120","author":"Bellas","year":"2023","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"veae039","DOI":"10.1093\/ve\/veae039","article-title":"Widespread occurrence and diverse origins of polintoviruses influence lineage-specific genome dynamics in stony corals","volume":"10","author":"Stephens","year":"2024","journal-title":"Virus Evol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"283","DOI":"10.1007\/s00705-023-05906-3","article-title":"Taxonomic update for giant viruses in the order Imitervirales (phylum Nucleocytoviricota)","volume":"168","author":"Aylward","year":"2023","journal-title":"Arch. Virol."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Aylward, F.O., Moniruzzaman, M., Ha, A.D., and Koonin, E.V. (2021). A phylogenomic framework for charting the diversity and evolution of giant viruses. PLoS Biol., 19.","DOI":"10.1101\/2021.05.05.442809"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"332","DOI":"10.1038\/s41564-022-01305-7","article-title":"Isolation and infection cycle of a polinton-like virus virophage in an abundant marine alga","volume":"8","author":"Roitman","year":"2023","journal-title":"Nat. Microbiol."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Nash, D., Palermo, C.N., Inamoto, I., Charles, T.C., Nissimov, J.I., and Short, S.M. (2025). Hybrid sequencing reveals the genome of a Chrysochromulina parva virus and highlight its distinct replication strategy. BMC Genom., 26.","DOI":"10.1186\/s12864-025-11700-z"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Stough, J.M.A., Yutin, N., Chaban, Y.V., Moniruzzaman, M., Gann, E.R., Pound, H.L., Steffen, M.M., Black, J.N., Koonin, E.V., and Wilhelm, S.W. (2019). Genome and environmental activity of a Chrysochromulina parva virus and its virophages. Front. Microbiol., 10.","DOI":"10.3389\/fmicb.2019.00703"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1016\/j.virol.2015.09.005","article-title":"Isolation and characterization of a virus infecting the freshwater algae Chrysochromulina parva","volume":"486","author":"Mirza","year":"2015","journal-title":"Virology"},{"key":"ref_30","first-page":"307","article-title":"Chrysochromulina: Genomic assessment and taxonomic diagnosis of the type species for an oleaginous algal clade","volume":"37","author":"Hovde","year":"2019","journal-title":"Algal Res.-Biomass Biofuels Bioprod."},{"key":"ref_31","first-page":"101492","article-title":"Naked Chrysochromulina (Haptophyta) isolates from lake and river ecosystems: An electron microscopic comparison including new observations on the type species of this taxon","volume":"40","author":"Deodato","year":"2019","journal-title":"Algal Res.-Biomass Biofuels Bioprod."},{"key":"ref_32","unstructured":"Andersen, R.A. (2005). Algal Culturing Techniques, Elsevier Academic Press."},{"key":"ref_33","unstructured":"Joshi, N.A., and Fass, J.N. (2011). Sickle: A Sliding-Window, Adaptive, Quality-Based Trimming Tool for FastQ Files, GitHub."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1038\/nmeth.3176","article-title":"Fast and sensitive protein alignment using DIAMOND","volume":"12","author":"Buchfink","year":"2015","journal-title":"Nat. Methods"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"6","DOI":"10.1186\/s13062-018-0208-7","article-title":"MEGAN-LR: New algorithms allow accurate binning and easy interactive exploration of metagenomic long reads and contigs","volume":"13","author":"Huson","year":"2018","journal-title":"Biol. Direct"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"msae263","DOI":"10.1093\/molbev\/msae263","article-title":"MEGA12: Molecular evolutionary genetic analysis version 12 for adaptive and green computing","volume":"41","author":"Kumar","year":"2024","journal-title":"Mol. Biol. Evol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"783","DOI":"10.1111\/j.1558-5646.1985.tb00420.x","article-title":"Confidence limits on phylogenies\u2014An approach using the bootstrap","volume":"39","author":"Felsenstein","year":"1985","journal-title":"Evolution"},{"key":"ref_38","first-page":"406","article-title":"The neighbor-joining method\u2014A new method for reconstructing phylogenetic trees","volume":"4","author":"Saitou","year":"1987","journal-title":"Mol. Biol. Evol."},{"key":"ref_39","first-page":"275","article-title":"The rapid generation of mutation data matrices from protein sequences","volume":"8","author":"Jones","year":"1992","journal-title":"Comput. Appl. Biosci."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"676","DOI":"10.1038\/nmeth.2019","article-title":"Fiji: An open-source platform for biological-image analysis","volume":"9","author":"Schindelin","year":"2012","journal-title":"Nat. Methods"},{"key":"ref_41","first-page":"1660","article-title":"Reconsideration of the derivation of Most Probable Numbers, their standard deviations, confidence bounds and rarity values","volume":"109","author":"Jarvis","year":"2010","journal-title":"J. Appl. Microbiol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"2639","DOI":"10.1111\/j.1462-2920.2009.01988.x","article-title":"Quantitative PCR reveals transient and persistent algal viruses in Lake Ontario, Canada","volume":"11","author":"Short","year":"2009","journal-title":"Environ. Microbiol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"810","DOI":"10.1038\/ismej.2010.183","article-title":"Quantification of virus genes provides evidence for seed-bank populations of phycodnaviruses in Lake Ontario, Canada","volume":"5","author":"Short","year":"2011","journal-title":"ISME J."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1","DOI":"10.21775\/cimb.040.001","article-title":"The virophage family Lavidaviridae","volume":"40","author":"Fischer","year":"2021","journal-title":"Curr. Issues Mol. Biol."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"e00230-17","DOI":"10.1128\/JVI.00230-17","article-title":"Comparative genomics of Chrysochromulina ericina virus and other microalga-infecting large DNA viruses highlights their intricate evolutionary relationship with the established Mimiviridae family","volume":"91","author":"Blanc","year":"2017","journal-title":"J. Virol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"493","DOI":"10.1016\/j.jmb.2005.08.060","article-title":"Cryo-electron microscopy of the giant mimivirus","volume":"353","author":"Xiao","year":"2005","journal-title":"J. Mol. Biol."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1602","DOI":"10.1038\/ismej.2015.240","article-title":"Seasonal determinations of algal virus decay rates reveal overwintering in a temperate freshwater pond","volume":"10","author":"Long","year":"2016","journal-title":"ISME J."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"e2314606121","DOI":"10.1073\/pnas.2314606121","article-title":"Endogenous virophages are active and mitigate giant virus infection in the marine protist Cafeteria burkhardae","volume":"121","author":"Hackl","year":"2024","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"E5318","DOI":"10.1073\/pnas.1506469112","article-title":"Provirophages in the Bigelowiella genome bear testimony to past encounters with giant viruses","volume":"112","author":"Blanc","year":"2015","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"18078","DOI":"10.1073\/pnas.1208835109","article-title":"Provirophages and transpovirons as the diverse mobilome of giant viruses","volume":"109","author":"Desnues","year":"2012","journal-title":"Proc. Natl. Acad. Sci. USA"}],"container-title":["Viruses"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4915\/18\/2\/196\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,2,6]],"date-time":"2026-02-06T10:11:37Z","timestamp":1770372697000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4915\/18\/2\/196"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,2,1]]},"references-count":50,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,2]]}},"alternative-id":["v18020196"],"URL":"https:\/\/doi.org\/10.3390\/v18020196","relation":{},"ISSN":["1999-4915"],"issn-type":[{"value":"1999-4915","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,2,1]]}}}