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1.
Elife ; 102021 10 26.
Artigo em Inglês | MEDLINE | ID: mdl-34698016

RESUMO

Virophages can parasitize giant DNA viruses and may provide adaptive anti-giant virus defense in unicellular eukaryotes. Under laboratory conditions, the virophage mavirus integrates into the nuclear genome of the marine flagellate Cafeteria burkhardae and reactivates upon superinfection with the giant virus CroV. In natural systems, however, the prevalence and diversity of host-virophage associations has not been systematically explored. Here, we report dozens of integrated virophages in four globally sampled C. burkhardae strains that constitute up to 2% of their host genomes. These endogenous mavirus-like elements (EMALEs) separated into eight types based on GC-content, nucleotide similarity, and coding potential and carried diverse promoter motifs implicating interactions with different giant viruses. Between host strains, some EMALE insertion loci were conserved indicating ancient integration events, whereas the majority of insertion sites were unique to a given host strain suggesting that EMALEs are active and mobile. Furthermore, we uncovered a unique association between EMALEs and a group of tyrosine recombinase retrotransposons, revealing yet another layer of parasitism in this nested microbial system. Our findings show that virophages are widespread and dynamic in wild Cafeteria populations, supporting their potential role in antiviral defense in protists.


Assuntos
Genoma/fisiologia , Retroelementos/fisiologia , Estramenópilas/genética , Estramenópilas/virologia , Virófagos/fisiologia , Filogenia
2.
Microbiome ; 9(1): 13, 2021 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-33436089

RESUMO

BACKGROUND: Polintons are large mobile genetic elements found in the genomes of eukaryotic organisms that are considered the ancient ancestors of most eukaryotic dsDNA viruses. Originally considered as transposons, they have been found to encode virus capsid genes, suggesting they may actually be integrated viruses; however, an extracellular form has yet to be detected. Recently, circa 25 Polinton-like viruses have been discovered in environmental metagenomes and algal genomes, which shared distantly related genes to both Polintons and virophages (Lavidaviridae). These entities could be the first members of a major class of ancient eukaryotic viruses; however, owing to the lack of available genomes for analysis, information on their global diversity, evolutionary relationships, eukaryotic hosts, and status as free virus particles is limited. RESULTS: Here, we analysed the metaviromes of an alpine lake to show that Polinton-like virus genome sequences are abundant in the water column. We identify major capsid protein genes belonging to 82 new Polinton-like viruses and use these to interrogate publicly available metagenomic datasets, identifying 543 genomes and a further 16 integrated into eukaryotic genomes. Using an analysis of shared gene content and major capsid protein phylogeny, we define large groups of Polinton-like viruses and link them to diverse eukaryotic hosts, including a new group of viruses, which possess all the core genes of virophages and infect oomycetes and Chrysophyceae. CONCLUSIONS: Our study increased the number of known Polinton-like viruses by 25-fold, identifying five major new groups of eukaryotic viruses, which until now have been hidden in metagenomic datasets. The large enrichment (> 100-fold) of Polinton-like virus sequences in the virus-sized fraction of this alpine lake and the fact that their viral major capsid proteins are found in eukaryotic host transcriptomes support the hypothesis that Polintons in unicellular eukaryotes are viruses. In summary, our data reveals a diverse assemblage of globally distributed viruses, associated with a wide range of unicellular eukaryotic hosts. We anticipate that the methods we have developed for Polinton-like virus detection and the database of over 20,000 genes we present will allow for continued discovery and analysis of these new viral groups. Video abstract.


Assuntos
Organismos Aquáticos/genética , Organismos Aquáticos/virologia , Vírus de DNA/genética , Eucariotos/genética , Eucariotos/virologia , Genoma Viral/genética , Lagos , Vírus de DNA/classificação , DNA Viral/genética , Ecossistema , Filogenia , Virófagos/genética , Integração Viral/genética
3.
Curr Issues Mol Biol ; 40: 1-24, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-32089519

RESUMO

Double-stranded (ds) DNA viruses of the family Lavidaviridae, commonly known as virophages, are a fascinating group of eukaryotic viruses that depend on a coinfecting giant dsDNA virus of the Mimiviridae for their propagation. Instead of replicating in the nucleus, virophages multiply in the cytoplasmic virion factory of a coinfecting giant virus inside a phototrophic or heterotrophic protistal host cell. Virophages are parasites of giant viruses and can inhibit their replication, which may lead to increased survival rates of the infected host cell population. The genomes of virophages are 17-33 kilobase pairs (kbp) long and encode 16-34 proteins. Genetic signatures of virophages can be found in metagenomic datasets from various saltwater and freshwater environments around the planet. Most virophages share a set of conserved genes that code for a major and a minor capsid protein, a cysteine protease, a genome-packaging ATPase, and a superfamily 3 helicase, although the genomes are otherwise diverse and variable. Lavidaviruses share genes with other mobile genetic elements, suggesting that horizontal gene transfer and recombination have been major forces in shaping these viral genomes. Integrases are occasionally found in virophage genomes and enable these DNA viruses to persist as provirophages in the chromosomes of their viral and cellular hosts. As we watch the genetic diversity of this new viral family unfold through metagenomics, additional isolates are still lacking and critical questions regarding their infection cycle, host range, and ecology remain to be answered.


Assuntos
Variação Genética , Genoma Viral , Metagenoma , Virófagos/classificação , Virófagos/genética , Capsídeo/química , Coinfecção , DNA Viral/genética , Evolução Molecular , Transferência Genética Horizontal , Vírus Gigantes/classificação , Vírus Gigantes/genética , Interações entre Hospedeiro e Microrganismos , Especificidade de Hospedeiro , Metagenômica/métodos , Filogenia , Replicação Viral
4.
Commun Biol ; 3(1): 248, 2020 05 21.
Artigo em Inglês | MEDLINE | ID: mdl-32439847

RESUMO

Virus adaptation to new hosts is a major cause of infectious disease emergence. This mechanism has been intensively studied in the context of zoonotic virus spillover, due to its impact on global health. However, it remains unclear for virophages, parasites of giant viruses and potential regulators of microbial communities. Here, we present, for the first time to our knowledge, evidence of cross-species infection of a virophage. We demonstrated that challenging the native population of Guarani virophage with two previously unidentified giant viruses, previously nonpermissive to this virophage, allows the selection of a mutant genotype able to infect these giant viruses. We were able to characterize the potential genetic determinant (deletion) carried by the virophage with the expanded-host range. Our study also highlights the relevant biological impact of this host adaptation by demonstrating that coinfection with the mixture containing the mutant virophage abolishes giant virus production and rescues the host cell population from lysis.


Assuntos
Acanthamoeba castellanii/virologia , Sobrevivência Celular , Vírus Gigantes/fisiologia , Interações Hospedeiro-Patógeno , Mimiviridae/fisiologia , Virófagos/fisiologia
5.
J Virol ; 94(11)2020 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-32188734

RESUMO

Virophages are small parasitic double-stranded DNA (dsDNA) viruses of giant dsDNA viruses infecting unicellular eukaryotes. Except for a few isolated virophages characterized by parasitization mechanisms, features of virophages discovered in metagenomic data sets remain largely unknown. Here, the complete genomes of seven virophages (26.6 to 31.5 kbp) and four large DNA viruses (190.4 to 392.5 kbp) that coexist in the freshwater lake Dishui Lake, Shanghai, China, have been identified based on environmental metagenomic investigation. Both genomic and phylogenetic analyses indicate that Dishui Lake virophages (DSLVs) are closely related to each other and to other lake virophages, and Dishui Lake large DNA viruses are affiliated with the micro-green alga-infecting Prasinovirus of the Phycodnaviridae (named Dishui Lake phycodnaviruses [DSLPVs]) and protist (protozoan and alga)-infecting Mimiviridae (named Dishui Lake large alga virus [DSLLAV]). The DSLVs possess more genes with closer homology to that of large alga viruses than to that of giant protozoan viruses. Furthermore, the DSLVs are strongly associated with large green alga viruses, including DSLPV4 and DSLLAV1, based on codon usage as well as oligonucleotide frequency and correlation analyses. Surprisingly, a nonhomologous CRISPR-Cas like system is found in DSLLAV1, which appears to protect DSLLAV1 from the parasitization of DSLV5 and DSLV8. These results suggest that novel cell-virus-virophage (CVv) tripartite infection systems of green algae, large green alga virus (Phycodnaviridae- and Mimiviridae-related), and virophage exist in Dishui Lake, which will contribute to further deep investigations of the evolutionary interaction of virophages and large alga viruses as well as of the essential roles that the CVv plays in the ecology of algae.IMPORTANCE Virophages are small parasitizing viruses of large/giant viruses. To our knowledge, the few isolated virophages all parasitize giant protozoan viruses (Mimiviridae) for propagation and form a tripartite infection system with hosts, here named the cell-virus-virophage (CVv) system. However, the CVv system remains largely unknown in environmental metagenomic data sets. In this study, we systematically investigated the metagenomic data set from the freshwater lake Dishui Lake, Shanghai, China. Consequently, four novel large alga viruses and seven virophages were discovered to coexist in Dishui Lake. Surprisingly, a novel CVv tripartite infection system comprising green algae, large green alga viruses (Phycodnaviridae- and Mimiviridae-related), and virophages was identified based on genetic link, genomic signature, and CRISPR system analyses. Meanwhile, a nonhomologous CRISPR-like system was found in Dishui Lake large alga viruses, which appears to protect the virus host from the infection of Dishui Lake virophages (DSLVs). These findings are critical to give insight into the potential significance of CVv in global evolution and ecology.


Assuntos
Clorófitas/virologia , DNA Viral/genética , Filogenia , Virófagos , Microbiologia da Água , China , Lagos , Metagenômica , Virófagos/classificação , Virófagos/genética
6.
ISME J ; 14(3): 727-739, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31822788

RESUMO

Acanthamoeba-infecting Mimiviridae are giant viruses with dsDNA genome up to 1.5 Mb. They build viral factories in the host cytoplasm in which the nuclear-like virus-encoded functions take place. They are themselves the target of infections by 20-kb-dsDNA virophages, replicating in the giant virus factories and can also be found associated with 7-kb-DNA episomes, dubbed transpovirons. Here we isolated a virophage (Zamilon vitis) and two transpovirons respectively associated to B- and C-clade mimiviruses. We found that the virophage could transfer each transpoviron provided the host viruses were devoid of a resident transpoviron (permissive effect). If not, only the resident transpoviron originally isolated from the corresponding virus was replicated and propagated within the virophage progeny (dominance effect). Although B- and C-clade viruses devoid of transpoviron could replicate each transpoviron, they did it with a lower efficiency across clades, suggesting an ongoing process of adaptive co-evolution. We analysed the proteomes of host viruses and virophage particles in search of proteins involved in this adaptation process. This study also highlights a unique example of intricate commensalism in the viral world, where the transpoviron uses the virophage to propagate and where the Zamilon virophage and the transpoviron depend on the giant virus to replicate, without affecting its infectious cycle.


Assuntos
Acanthamoeba/virologia , Mimiviridae/fisiologia , Vírus Gigantes/genética , Vírus Gigantes/fisiologia , Mimiviridae/genética , Mimiviridae/crescimento & desenvolvimento , Mimiviridae/isolamento & purificação , Simbiose , Virófagos/genética , Virófagos/fisiologia
7.
Microbiome ; 7(1): 157, 2019 12 10.
Artigo em Inglês | MEDLINE | ID: mdl-31823797

RESUMO

BACKGROUND: Virophages are small viruses with double-stranded DNA genomes that replicate along with giant viruses and co-infect eukaryotic cells. Due to the paucity of virophage reference genomes, a collective understanding of the global virophage diversity, distribution, and evolution is lacking. RESULTS: Here we screened a public collection of over 14,000 metagenomes using the virophage-specific major capsid protein (MCP) as "bait." We identified 44,221 assembled virophage sequences, of which 328 represent high-quality (complete or near-complete) genomes from diverse habitats including the human gut, plant rhizosphere, and terrestrial subsurface. Comparative genomic analysis confirmed the presence of four core genes in a conserved block. We used these genes to establish a revised virophage classification including 27 clades with consistent genome length, gene content, and habitat distribution. Moreover, for eight high-quality virophage genomes, we computationally predicted putative eukaryotic virus hosts. CONCLUSION: Overall, our approach has increased the number of known virophage genomes by 10-fold and revealed patterns of genome evolution and global virophage distribution. We anticipate that the expanded diversity presented here will provide the backbone for further virophage studies.


Assuntos
DNA Viral/genética , Genoma Viral/genética , Metagenoma/genética , Metagenômica/métodos , Virófagos/classificação , Bases de Dados Genéticas , Filogenia , Virófagos/genética
8.
Virol J ; 16(1): 126, 2019 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-31684962

RESUMO

Since the discovery of mimivirus, numerous giant viruses associated with free-living amoebae have been described. The genome of giant viruses can be more than 2.5 megabases, and virus particles can exceed the size of many bacteria. The unexpected characteristics of these viruses have made them intriguing research targets and, as a result, studies focusing on their interactions with their amoeba host have gained increased attention. Studies have shown that giant viruses can establish host-pathogen interactions, which have not been previously demonstrated, including the unprecedented interaction with a new group of small viruses, called virophages, that parasitize their viral factories. In this brief review, we present recent advances in virophage-giant virus-host interactions and highlight selected studies involving interactions between giant viruses and amoebae. These unprecedented interactions involve the giant viruses mimivirus, marseillevirus, tupanviruses and faustovirus, all of which modulate the amoeba environment, affecting both their replication and their spread to new hosts.


Assuntos
Amoeba/virologia , Vírus Gigantes/fisiologia , Interações Hospedeiro-Patógeno , Amoeba/fisiologia , Vesículas Extracelulares/metabolismo , Vesículas Extracelulares/virologia , Genoma Viral , Especificidade de Hospedeiro , Mimiviridae/fisiologia , Modelos Biológicos , Virófagos/fisiologia , Replicação Viral
9.
Viruses ; 11(8)2019 08 08.
Artigo em Inglês | MEDLINE | ID: mdl-31398856

RESUMO

The last decade has been marked by two eminent discoveries that have changed our perception of the virology field: The discovery of giant viruses and a distinct new class of viral agents that parasitize their viral factories, the virophages. Coculture and metagenomics have actively contributed to the expansion of the virophage family by isolating dozens of new members. This increase in the body of data on virophage not only revealed the diversity of the virophage group, but also the relevant ecological impact of these small viruses and their potential role in the dynamics of the microbial network. In addition, the isolation of virophages has led us to discover previously unknown features displayed by their host viruses and cells. In this review, we present an update of all the knowledge on the isolation, biology, genomics, and morphological features of the virophages, a decade after the discovery of their first member, the Sputnik virophage. We discuss their parasitic lifestyle as bona fide viruses of the giant virus factories, genetic parasites of their genomes, and then their role as a key component or target for some host defense mechanisms during the tripartite virophage-giant virus-host cell interaction. We also present the latest advances regarding their origin, classification, and definition that have been widely discussed.


Assuntos
Vírus Gigantes/fisiologia , Virófagos/fisiologia , Animais , Evolução Biológica , Genoma Viral , Genômica/métodos , Vírus Gigantes/isolamento & purificação , Vírus Gigantes/ultraestrutura , História do Século XXI , Interações Hospedeiro-Patógeno , Humanos , Sequências Repetitivas Dispersas , Estágios do Ciclo de Vida , Metagenômica/métodos , Pesquisa/história , Virologia/história , Virófagos/classificação , Virófagos/isolamento & purificação , Virófagos/ultraestrutura
10.
Ann N Y Acad Sci ; 1447(1): 97-109, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31162694

RESUMO

DNA viruses with efficient host genome integration capability were unknown in eukaryotes until recently. The discovery of virophages, satellite-like DNA viruses that depend on lytic giant viruses that infect protists, revealed a genetically diverse group of viruses with high genome mobility. Virophages can act as strong inhibitors of their associated giant viruses, and the resulting beneficial effects on their unicellular hosts resemble a population-based antiviral defense mechanism. By comparing various aspects of genome-integrating virophages, in particular the virophage mavirus, with other mobile genetic elements and parasite-derived defense mechanisms in eukaryotes and prokaryotes, we show that virophages share many features with other host-parasite systems. Yet, the dual lifestyle exhibited by mavirus remains unprecedented among eukaryotic DNA viruses, with potentially far-reaching ecological and evolutionary consequences for the host.


Assuntos
Genoma Viral/fisiologia , Interações Hospedeiro-Parasita/fisiologia , Virófagos/genética , Virófagos/metabolismo , Animais , Humanos
12.
J Mol Evol ; 87(1): 7-15, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30456441

RESUMO

The definition of a genomic signature (GS) is "the total net response to selective pressure". Recent isolation and sequencing of naturally occurring organisms, hereby named entoorganisms, within Acanthamoeba polyphaga, raised the hypothesis of a common genomic signature despite their diverse and unrelated evolutionary origin. Widely accepted and implemented tests for GS detection are oligonucleotide relative frequencies (OnRF) and relative codon usage (RCU) surveys. A common pattern and strong correlations were unveiled from OnRFs among A. polyphaga's Mimivirus and virophage Sputnik. RCU showed a common A-T bias at third codon position. We expanded tests to the amoebal mitochondrial genome and amoeba-resistant bacteria, achieving strikingly coherent results to the aforementioned viral analyses. The GSs in these entoorganisms of diverse evolutionary origin are coevolutionarily conserved within an intracellular environment that provides sanctuary for species of ecological and biomedical relevance.


Assuntos
Acanthamoeba/genética , Coevolução Biológica/genética , Mimiviridae/genética , Amoeba/genética , Animais , Bactérias/genética , Códon/genética , Evolução Molecular , Genoma Viral , Genômica , Mitocôndrias/genética , Parasitos/genética , Proteínas Virais/genética , Virófagos/genética
13.
Acta Biochim Pol ; 65(4): 487-496, 2018 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-30444087

RESUMO

Five years after being discovered in 2003, some giant viruses were demonstrated to play a role of the hosts for virophages, their parasites, setting out a novel and yet unknown regulatory mechanism of the giant viruses presence in an aqueous. So far, 20 virophages have been registered and 13 of them have been described as a metagenomic material, which indirectly impacts the number of single- and multi-cell organisms, the environment where giant viruses replicate.


Assuntos
Vírus Gigantes/fisiologia , Virófagos/fisiologia , Genoma Viral , Vírus Gigantes/classificação , Vírus Gigantes/genética , Metagenômica , Filogenia , Virófagos/classificação , Virófagos/genética , Replicação Viral
14.
Braz J Microbiol ; 49 Suppl 1: 260-261, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30166269

RESUMO

Rio Negro virophage (RNV) was co-isolated with a strain of mimivirus named sambavirus, from Brazilian Amazon. We report the near complete genome sequence of RNV, the first virophage isolated in Brazil. We also present new microscopical data demonstrating that RNV particles have similar dimensions to that described to sputnik virophages.


Assuntos
Acanthamoeba/virologia , Genoma Viral , Togaviridae/genética , Virófagos/genética , Brasil , Microscopia Eletrônica de Transmissão , Fases de Leitura Aberta , Filogenia , Togaviridae/isolamento & purificação , Togaviridae/ultraestrutura , Virófagos/isolamento & purificação , Virófagos/ultraestrutura
15.
Curr Opin Virol ; 31: 1-8, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-30071360

RESUMO

Viruses are ubiquitous parasites of cellular life forms and the most abundant biological entities on earth. The relationships between viruses and their hosts involve the continuous arms race but are by no account limited to it. Growing evidence shows that, in the course of evolution, viruses and their components are repeatedly recruited (exapted) for host functions. The functions of exapted viruses typically involve either defense from other viruses or cellular competitors or transfer of nucleic acids between cells, or storage functions. Virus exaptation can reach different depths, from recruitment of a fully functional virus to exploitation of defective, partially degraded viruses, to utilization of individual virus proteins.


Assuntos
Evolução Molecular , Interações Hospedeiro-Patógeno , Vírus/genética , Animais , Vírus de DNA/fisiologia , Genoma Viral , Interações entre Hospedeiro e Microrganismos , Humanos , Provírus/genética , Proteínas Virais , Virófagos/genética , Vírus/patogenicidade
16.
Proc Natl Acad Sci U S A ; 115(28): 7332-7337, 2018 07 10.
Artigo em Inglês | MEDLINE | ID: mdl-29941605

RESUMO

Virophages have the unique property of parasitizing giant viruses within unicellular hosts. Little is understood about how they form infectious virions in this tripartite interplay. We provide mechanistic insights into assembly and maturation of mavirus, a marine virophage, by combining structural and stability studies on capsomers, virus-like particles (VLPs), and native virions. We found that the mavirus protease processes the double jelly-roll (DJR) major capsid protein (MCP) at multiple C-terminal sites and that these sites are conserved among virophages. Mavirus MCP assembled in Escherichia coli in the absence and presence of penton protein, forming VLPs with defined size and shape. While quantifying VLPs in E. coli lysates, we found that full-length rather than processed MCP is the competent state for capsid assembly. Full-length MCP was thermally more labile than truncated MCP, and crystal structures of both states indicate that full-length MCP has an expanded DJR core. Thus, we propose that the MCP C-terminal domain serves as a scaffolding domain by adding strain on MCP to confer assembly competence. Mavirus protease processed MCP more efficiently after capsid assembly, which provides a regulation mechanism for timing capsid maturation. By analogy to Sputnik and adenovirus, we propose that MCP processing renders mavirus particles infection competent by loosening interactions between genome and capsid shell and destabilizing pentons for genome release into host cells. The high structural similarity of mavirus and Sputnik capsid proteins together with conservation of protease and MCP processing suggest that assembly and maturation mechanisms described here are universal for virophages.


Assuntos
Proteínas do Capsídeo , Peptídeo Hidrolases , Vírion , Virófagos , Montagem de Vírus/fisiologia , Proteínas do Capsídeo/química , Proteínas do Capsídeo/genética , Proteínas do Capsídeo/metabolismo , Peptídeo Hidrolases/química , Peptídeo Hidrolases/genética , Peptídeo Hidrolases/metabolismo , Vírion/química , Vírion/genética , Vírion/metabolismo , Virófagos/química , Virófagos/fisiologia
17.
Virus Res ; 251: 14-16, 2018 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-29715483

RESUMO

Giant viruses infect protozoa, especially amoebae of the genus Acanthamoeba. These viruses possess genetic elements named Mobilome. So far, this mobilome comprises provirophages which are integrated into the genome of their hosts, transpovirons, and Maverick/Polintons. Virophages replicate inside virus factories within Acanthamoeba and can decrease the infectivity of giant viruses. The virophage infecting CroV was found to be integrated in the host of CroV, Cafeteria roenbergensis, thus protecting C. roenbergensis by reduction of CroV multiplication. Because of this unique property, assessment of the mechanisms of replication of virophages and their relationship with giant viruses is a key element of this investigation. This work aimed at evaluating the presence and the dynamic of these mobile elements in sixteen Acanthamoeba genomes. No significant traces of the integration of genomes or sequences from known virophages were identified in all the available Acanthamoeba genomes. These results brought us to hypothesize that the interactions between mimiviruses and their virophages might occur through different mechanisms, or at low frequency. An additional explanation could be that our knowledge of the diversity of virophages is still very limited.


Assuntos
Acanthamoeba/genética , Acanthamoeba/virologia , Vírus Gigantes/genética , Sequências Repetitivas Dispersas , Virófagos/genética , Vírus Gigantes/crescimento & desenvolvimento , Virófagos/crescimento & desenvolvimento , Replicação Viral
18.
Braz. j. microbiol ; 49(supl.1): 260-261, 2018. graf
Artigo em Inglês | LILACS | ID: biblio-974329

RESUMO

ABSTRACT Rio Negro virophage (RNV) was co-isolated with a strain of mimivirus named sambavirus, from Brazilian Amazon. We report the near complete genome sequence of RNV, the first virophage isolated in Brazil. We also present new microscopical data demonstrating that RNV particles have similar dimensions to that described to sputnik virophages.


Assuntos
Togaviridae/genética , Acanthamoeba/virologia , Genoma Viral , Virófagos/genética , Filogenia , Togaviridae/isolamento & purificação , Togaviridae/ultraestrutura , Brasil , Fases de Leitura Aberta , Microscopia Eletrônica de Transmissão , Virófagos/isolamento & purificação , Virófagos/ultraestrutura
19.
Nat Commun ; 8(1): 858, 2017 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-29021524

RESUMO

Virophages are small viruses that co-infect eukaryotic cells alongside giant viruses (Mimiviridae) and hijack their machinery to replicate. While two types of virophages have been isolated, their genomic diversity and ecology remain largely unknown. Here we use time series metagenomics to identify and study the dynamics of 25 uncultivated virophage populations, 17 of which represented by complete or near-complete genomes, in two North American freshwater lakes. Taxonomic analysis suggests that these freshwater virophages represent at least three new candidate genera. Ecologically, virophage populations are repeatedly detected over years and evolutionary stable, yet their distinct abundance profiles and gene content suggest that virophage genera occupy different ecological niches. Co-occurrence analyses reveal 11 virophages strongly associated with uncultivated Mimiviridae, and three associated with eukaryotes among the Dinophyceae, Rhizaria, Alveolata, and Cryptophyceae groups. Together, these findings significantly augment virophage databases, help refine virophage taxonomy, and establish baseline ecological hypotheses and tools to study virophages in nature.Virophages are recently-identified small viruses that infect larger viruses, yet their diversity and ecological roles are poorly understood. Here, Roux and colleagues present time series metagenomics data revealing new virophage genera and their putative ecological interactions in two freshwater lakes.


Assuntos
Ecossistema , Eucariotos/virologia , Lagos/virologia , Mimiviridae , Virófagos/genética , Genoma Viral , Metagenoma , Metagenômica
20.
Curr Opin Virol ; 25: 59-65, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28802203

RESUMO

Virophages and polintons are part of a complex system that also involves eukaryotes, giant viruses, as well as other viruses and transposable elements. Virophages are cosmopolitan, being found in environments ranging from the Amazon River to Antarctic hypersaline lakes, while polintons are found in many single celled and multicellular eukaryotes. Virophages and polintons have a shared ancestry, but their exact origins are unknown and obscured by antiquity and extensive horizontal gene transfer (HGT). Paleovirology can help disentangle the complicated gene flow between these two, as well as their giant viral and eukaryotic hosts. We outline the evidence and theoretical support for polintons being descended from viruses and not vice versa. In order to disentangle the natural history of polintons and virophages, we suggest that there is much to be gained by embracing rigorous metagenomics and evolutionary analyses. Methods from paleovirology will play a pivotal role in unravelling ancient relationships, HGT and patterns of cross-species transmission.


Assuntos
Elementos de DNA Transponíveis/genética , Eucariotos/virologia , Evolução Molecular , Vírus Gigantes/genética , Virófagos/genética , DNA Viral/genética , Transferência Genética Horizontal , Genoma Viral , Vírus Gigantes/fisiologia , Filogenia , Viroses/genética , Viroses/transmissão
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