A DNA virus is a virus that has DNA as its genetic material and replicates using a DNA-dependent DNA polymerase. The nucleic acid is usually double-stranded DNA (dsDNA) but may also be single-stranded DNA (ssDNA). DNA viruses belong to either Group I or Group II of the Baltimore classification system for viruses. Single-stranded DNA is usually expanded to double-stranded in infected cells. Although Group VII viruses such as hepatitis B contain a DNA genome, they are not considered DNA viruses according to the Baltimore classification, but rather reverse transcribing viruses because they replicate through an RNA intermediate. Notable diseases like smallpox and chickenpox are caused by such DNA viruses.
- 1 Group I: dsDNA viruses
- 2 Group II: ssDNA viruses
- 3 Satellite viruses
- 4 Phylogenetic relationships
- 5 Bacteriophage evolution
- 6 NCLDVs
- 7 References
- 8 Additional reading
Group I: dsDNA viruses
Genome organization within this group varies considerably. Some have circular genomes (Baculoviridae, Papovaviridae and Polydnaviridae) while others have linear genomes (Adenoviridae, Herpesviridae and some phages). Some families have circularly permuted linear genomes (phage T4 and some Iridoviridae). Others have linear genomes with covalently closed ends (Poxviridae and Phycodnaviridae).
A virus infecting archaea was first described in 1974. Several others have been described since: most have head-tail morphologies and linear double-stranded DNA genomes. Other morphologies have also been described: spindle shaped, rod shaped, filamentous, icosahedral and spherical. Additional morphological types may exist.
Orders within this group are defined on the basis of morphology rather than DNA sequence similarity. It is thought that morphology is more conserved in this group than sequence similarity or gene order which is extremely variable. Three orders and 31 families are currently recognised. A fourth order – Megavirales – for the nucleocytoplasmic large DNA viruses has been proposed. Four genera are recognised that have not yet been assigned a family. The species Sulfolobus turreted icosahedral virus is so unlike any previously described virus that it will almost certainly be placed in a new family on the next revision of viral families.
Fifteen families are enveloped. These include all three families in the order Herpesvirales and the following families: Ascoviridae, Ampullaviridae, Asfarviridae, Baculoviridae, Fuselloviridae, Globuloviridae, Guttaviridae, Hytrosaviridae, Iridoviridae, Lipothrixviridae, Nimaviridae and Poxviridae.
Bacteriophages (viruses infecting bacteria) belonging to the families Tectiviridae and Corticoviridae have a lipid bilayer membrane inside the icosahedral protein capsid and the membrane surrounds the genome. The crenarchaeal virus Sulfolobus turreted icosahedral virus has a similar structure.
The genomes in this group vary considerably from ~10 kilobases to over 2.5 megabases in length. The largest bacteriophage known is Klebsiella Phage vB_KleM-RaK2 which has a genome of 346 kilobases.
Species of the order Caudovirales and of the families Corticoviridae and Tectiviridae infect bacteria.
Species of the order Ligamenvirales and the families Ampullaviridae, Bicaudaviridae, Clavaviridae, Fuselloviridae, Globuloviridae and Guttaviridae infect hyperthermophilic archaea species of the Crenarchaeota.
Species of the order Herpesvirales and of the families Adenoviridae, Asfarviridae, Iridoviridae, Papillomaviridae, Polyomaviridae and Poxviridae infect vertebrates.
Species of the families Ascovirus, Baculovirus, Hytrosaviridae, Iridoviridae and Polydnaviruses and of the genus Nudivirus infect insects.
Species of the family Mimiviridae and the species Marseillevirus, Megavirus, Mavirus virophage and Sputnik virophage infect protozoa.
Species of the family Nimaviridae infect crustaceans.
Species of the family Plasmaviridae infect species of the class Mollicutes.
Species of the family Pandoraviridae infect amoebae.
Species of the genus Rhizidiovirus infect stramenopiles. These are the only known dsDNA viruses that infect stramenopiles.
Species of the genus Salterprovirus and Sphaerolipoviridae infect species of the Euryarchaeota.
- Order Caudovirales
- Order Herpesvirales
- Unassigned families
- Family Adenoviridae – includes viruses which cause human adenovirus infection
- Family Ampullaviridae
- Family Ascoviridae
- Family Asfarviridae – includes African swine fever virus
- Family Baculoviridae
- Family Bicaudaviridae
- Family Clavaviridae
- Family Corticoviridae
- Family Fuselloviridae
- Family Globuloviridae
- Family Guttaviridae
- Family Hytrosaviridae
- Family Iridoviridae
- Family Marseilleviridae
- Family Mimiviridae
- Family Nimaviridae
- Family Pandoraviridae
- Family Papillomaviridae
- Family Phycodnaviridae
- Family Plasmaviridae
- Family Polydnaviruses
- Family Polyomaviridae – includes Simian virus 40, JC virus, BK virus
- Family Poxviridae – includes Cowpox virus, smallpox
- Family Sphaerolipoviridae
- Family Tectiviridae
- Unassigned species
A group known as the pleolipoviruses, although having a similar genome organisation, differ in having either single or double stranded DNA genomes. Within the double stranded forms have runs of single stranded DNA. This group does not fit into the current classification system and a new taxon is required.
These viruses are nonlytic and form virions characterized by a lipid vesicle enclosing the genome. They do not have nucleoproteins. The lipids in the virla membrane are unselectively acquired from host cell membranes. The virions contain two to three major structural proteins, which either are embedded in the membrane or form spikes distributed randomly on the external membrane surface.
This group includes the following viruses:
- Haloarcula hispanica pleomorphic virus 1
- Halogeometricum pleomorphic virus 1
- Halorubrum pleomorphic virus 1
- Halorubrum pleomorphic virus 2
- Halorubrum pleomorphic virus 3
- Halorubrum pleomorphic virus 6
Group II: ssDNA viruses
Although bacteriophages were first described in 1927, it was only in 1959 that Sinshemer working with phage Phi X 174 showed that they could possess single-stranded DNA genomes. Despite this discovery until relatively recently it was believed that the majority of DNA viruses belonged to the double-stranded clade. Recent work suggests that this may not be the case with single-stranded viruses forming the majority of viruses found in sea water, fresh water, sediment, terrestrial, extreme, metazoan-associated and marine microbial mats. Many of these "environmental" viruses belong to the family Microviridae. However, the vast majority has yet to be classified and assigned to genera and higher taxa. Because most of these viruses do not appear to be related or are only distantly related to known viruses additional taxa will be created for these.
Families in this group have been assigned on the basis of the nature of the genome (circular or linear) and the host range. Nine families are currently recognised.
- Family Anelloviridae
- Family Bacillariodnaviridae
- Family Bidnaviridae
- Family Circoviridae
- Family Geminiviridae
- Family Inoviridae
- Family Microviridae
- Family Nanoviridae
- Family Parvoviridae
A division of the circular single stranded viruses into four types has been proposed. This division seems likely reflects their phylogenetic relationships.
Type I genomes are characterized by a small circular DNA genome (approximately 2-kb), with the Rep protein and the major open reading frame (ORF) in opposite orientations. This type is characteristic of the circoviruses, geminiviruses and nanoviruses.
Type II genomes have the unique feature of two separate Rep ORFs.
Type III genomes contain two major ORFs in the same orientation. This arrangement is typical of the anelloviruses.
Type IV genomes have the largest genomes of nearly 4-kb, with up to eight ORFs. This type of genome is found in the Inoviridae and the Microviridae.
Given the variety of single stranded viruses that have been described this scheme – if it is accepted by the ICTV – will need to be extended.
The families Bidnaviridae and Parvoviridae have linear genomes while the other families have circular genomes. The Bidnaviridae have a two part genome and infect invertebrates. The Inoviridae and Microviridae infect bacteria; the Anelloviridae and Circoviridae infect animals (mammals and birds respectively); and the Geminiviridae and Nanoviridae infect plants. In both the Geminiviridae and Nanoviridae the genome is composed of more than a single chromosome. The Bacillariodnaviridae infect diatoms and have a unique genome: the major chromosome is circular (~6 kilobases in length): the minor chromosome is linear (~1 kilobase in length) and complementary to part of the major chromosome.
All viruses in this group require formation of a replicative form – a double stranded DNA intermediate – for genome replication. This is normally created from the viral DNA with the assistance of the host's own DNA polymerase.
A number of additional single stranded DNA viruses have been described but are as yet unclassified.
- Animal viruses
Among these are the parvovirus like viruses. These have linear single stranded DNA genomes but unlike the parvoviruses the genome is bipartate. This group includes the Bombyx mori densovirus type 2, Hepatopancreatic parvo-like virus and Lymphoidal parvo-like virus. A new family Bidensoviridae has been proposed for this group but this proposal has not been ratified by the ICTV to date. Their closest relations appear to be the Brevidensoviruses (family Parvoviridae).
In the 9th edition of the viral taxonomy of the ICTV (published 2011) the Bombyx mori densovirus type 2 was placed in a new family – the Bidnaviridae on the basis of its genome structure and replication mechanism. This is currently the only member of this family but it seems likely that other species will be allocated to this family in the near future.
Another new genus – as yet unnamed – has been proposed. This genus includes the species bovine stool associated circular virus and chimpanzee stool associated circular virus. The closest relations to this genus appear to be the Nanoviridae but further work will be needed to confirm this. Another isolate that appears to be related to these viruses has been isolated from pig faeces in New Zealand. This isolate also appears to be related to the pig stool-associated single-stranded DNA virus. This virus has two large open reading frames one encoding the capsid gene and the other the Rep gene. These are bidirectionally transcribed and separated by intergenic regions. The name Gemycircularvirus has been proposed for this group of viruses. Another virus of this group has been reported again from pigs. Some of this group of viruses may infect fungi. An virus from this group has been isoalted from turkey faeces.
Fur seal feces-associated circular DNA virus was isolate from the faeces of a fur seal (Arctocephalus forsteri) in New Zealand. The genome has 2 main open reading frames and is 2925 nucleotides in length. Another virus porcine stool associated virus 4 has been isolated that appears to be related to the fur seal virus.
Two viruses have been isolated from human faeces - circo-like virus-Brazil hs1 and hs2 - with genome lengths of 2526 and 2533 nucleotides respectively. These viruses have four open reading frames. These viruses appear to be related to three viruses previously isolated from waste water, a bat and from a rodent.
Two viruses have been described from the nesting material yellow crowned parakeet (Cyanoramphus auriceps) – CynNCXV (2308 nt) and CynNCKV (2087 nt) Both viruses have two bidirectional open reading frames. Within these are the rolling-circle replication motifs I, II, III and the helicase motifs Walker A and Walker B. There is also a conserved nonanucleotide motif required for rolling-circle replication. CynNCKV has some similarity to the picobiliphyte nano-like virus (Picobiliphyte M5584-5) and CynNCXV has some similarity to the rodent stool associated virus (RodSCV M-45).
Psittacine beak and feather disease virus is a single stranded circular molecule of 1993 nucleotide bases encoding seven open reading frames — three in the virion strand and four in the complementary strand. The open reading frames have some homology to porcine circovirus, subterranean clover stunt virus and faba bean necrotic yellows virus.
A virus with a circular genome – sea turtle tornovirus 1 – has been isolated from a sea turtle with fibropapillomatosis. It is sufficiently unrelated to any other known virus that it may belong to a new family. The closest relations seem to be the Gyrovirinae. The proposed genus name for this virus is Tornovirus.
A virus — Acheta domesticus volvovirus has been isolated from the house cricket (Acheta domesticus). The genome is circular, has four open reading frames and is 2,517 nucleotides in length. It appears to be unrelated to previously described species. The genus name Volvovirus has been proposed for these species. The genomes in this genus are ~2.5 nucleotides in length and encode 4 open reading frames.
A virus has been isolated from the mud flat snail (Amphibola crenata). This virus has a single stranded circular genome of 2351 nucleotides that encoded 2 open reading frames that are oriented in opposite directions. The smaller open reading frame (874 nucleotides) encodes a protein with similarities to the Rep (replication) proteins of circoviruses and plasmids. The larger open reading frame (955 nucleotides) has no homology to any currently known protein.
An unusual – and as yet unnamed – virus has been isolated from the flatwom Girardia tigrina. Because of its genome organisation, this virus appears to belong to an entirely new family. It is the first virus to be isolated from a flatworm.
Ten new circular viruses have been isolated from dragonfly larvae. The genomes range from 1628 to 2668 nucleotides in length.
Most known fungal viruses have either double stranded DNA or RNA genomes. A single stranded DNA fungal virus – Sclerotinia sclerotiorum hypovirulence associated DNA virus 1 – has been described. This virus appears to be related to the Geminiviridae but is distinct from them. A genus – Breviviridae – has been proposed for Sclerotinia sclerotiorum hypovirulence associated DNA virus 1 and a European badger fecal virus.
A circular single stranded DNA virus has been isolated from a grapevine. This species may be related to the family Geminiviridae but differs from this family in a number of important respects including genome size.
A virus — Euphorbia caput medusae latent virus — is so divergent from the other members of the geminiviruses that a new genus has been proposed for it. The name of this new genus is proposed to be Capulavirus.
Several viruses — baminivirus, nepavirus and niminivirus — related to geminvirus have also been reported.
Although ~50 archaeal viruses are known, all but two have double stranded genomes. The first archaeal ssDNA virus to be isolated is the Halorubrum pleomorphic virus 1, which has a pleomorphic enveloped virion and a circular genome.
The second single stranded DNA virus infecting Archaea is Aeropyrum coil-shaped virus (ACV). The genome is circular and with 24,893 nucleotides is currently the largest known ssDNA genome. The viron is nonenveloped, hollow, cylindrical and formed from a coiling fiber. The morphology and the genome appear to be unique. ACV has been suggested to represent a new viral family tentatively called "Spiraviridae" (from Latin spira, "a coil").
- Marine and other
Several hundred single stranded DNA viral genomes have been isolated from seawater. Their hosts have yet to be identified but are likely to be eukaryotic phytoplankton and zooplankton. They fall into at least 11 distinct groups that are unrelated to previously described viral families.
A virus — Boiling Springs Lake virus — appears to have evolved by a recombination event between a DNA virus (circovirus) and an RNA virus (tombusvirus). The genome is circular and encodes two proteins — a Rep protein and a capsid protein.
Further reports of viruses that appear to have evolved from recombination events between ssRNA and ssDNA viruses have been made.
Satellite viruses are small viruses with either RNA or DNA as their genomic material that require another virus to replicate. There are two types of DNA satellite viruses – the alphasatellites and the betasatellites – both of which are dependent on begomaviruses. At present satellite viruses are not classified into genera or higher taxa.
Alphasatellites are small circular single strand DNA viruses that require a begomovirus for transmission. Betasatellites are small linear single stranded DNA viruses that require a begomovirus to replicate.
Phylogenetic relationships between these families are difficult to determine. The genomes differ significantly in size and organisation. Most studies that have attempted to determine these relationships are based either on some of the more conserved proteins – DNA polymerase and others – or on common structural features. In general most of the proposed relationships are tentative and have not yet been used by the ICTV in their classification.
ds DNA viruses
- Herpesviruses and caudoviruses
While determining the phylogenetic relations between the various known clades of viruses is difficult, on a number of grounds the herpesviruses and caudoviruses appear to be related.
While the three families in the order Herpesvirales are clearly related on morphological grounds, it has proven difficult to determine the dates of divergence between them because of the lack of gene conservation. On morphological grounds they appear to be related to the bacteriophages – specifically the Caudoviruses.
The branching order among the herpesviruses suggests that Alloherpesviridae is the basal clade and that Herpesviridae and Malacoherpesviridae are sister clades. Given the phylogenetic distances between vertebrates and molluscs this suggests that herpesviruses were initially fish viruses and that they have evolved with their hosts to infect other vertebrates.
The vertebrate herpesviruses initially evolved ~Pangaea. The alphaherpesvirinae separated from the branch leading to the betaherpesvirinae and gammaherpesvirinae about to . The avian herpes viruses diverged from the branch leading to the mammalian species. The mammalian species divided into two branches – the Simplexvirus and Varicellovirus genera. This latter divergence appears to have occur around the time of the mammalian radiation.and underwent subsequent evolution on the supercontinent
Several dsDNA bacteriophages and the herpesviruses encode a powerful ATP driven DNA translocating machine that encapsidates a viral genome into a preformed capsid shell or prohead. The critical components of the packaging machine are the packaging enzyme (terminase) which acts as the motor and the portal protein that forms the unique DNA entrance vertex of prohead. The terminase complex consists of a recognition subunit (small terminase) and an endonuclease/translocase subunit (large terminase) and cuts viral genome concatemers. It forms a motor complex containing five large terminase subunits. The terminase-viral DNA complex docks on the portal vertex. The pentameric motor processively translocates DNA until the head shell is full with one viral genome. The motor cuts the DNA again and dissociates from the full head, allowing head-finishing proteins to assemble on the portal, sealing the portal, and constructing a platform for tail attachment. Only a single gene encoding the putative ATPase subunit of the terminase (UL15) is conserved among all herpesviruses. To a lesser extent this gene is also found also in T4-like bacteriophages suggesting a common ancestor for these two groups of viruses.
A common origin for the herpesviruses and the caudoviruses has been suggested on the basis of parallels in their capsid assembly pathways and similarities between their portal complexes, through which DNA enters the capsid. These two groups of viruses share a distinctive 12-fold arrangement of subunits in the portal complex.
- Large DNA viruses
The family Ascoviridae appear to have evolved from the Iridoviridae. The family Polydnaviridae may have evolved from the Ascoviridae. Molecular evidence suggests that the Phycodnaviridae may have evolved from the family Iridoviridae. These four families (Ascoviridae, Iridoviridae, Phycodnaviridae and Polydnaviridae) may form a clade but more work is needed to confirm this.
Based on the genome organisation and DNA replication mechanism it seems that phylogenetic relationships may exist between the rudiviruses (Rudiviridae) and the large eukaryal DNA viruses: the African swine fever virus (Asfarviridae), Chlorella viruses (Phycodnaviridae) and poxviruses (Poxviridae).
Based on the analysis of the DNA polymerase the genus Dinodnavirus may be a member of the family Asfarviridae. Further work on this virus will required before a final assignment can be made.
The nucleocytoplasmic large DNA virus group (Asfarviridae, Iridoviridae, Marseilleviridae, Mimiviridae, Phycodnaviridae and Poxviridae) along with three other families – Adenoviridae, Cortiviridae and Tectiviridae – and the phage Sulfolobus turreted icosahedral virus and the satellite virus Sputnik all possess double β-barrel major capsid proteins suggesting a common origin.
- Other viruses
Based on the analysis of the coat protein, Sulfolobus turreted icosahedral virus may share a common ancestry with the Tectiviridae.
The families Adenoviridae and Tectiviridae appear to be related structurally.
Baculoviruses evolved from the nudiviruses .
The Hytrosaviridae are related to the baculoviruses and to a lesser extent the nudiviruses suggesting they may have evolved from the baculoviruses.
The Nimaviridae may be related to nudiviruses and baculoviruses.
The Nudiviruses seem to be related to the polydnaviruses.
A protein common to the families Bicaudaviridae, Lipotrixviridae and Rudiviridae and the unclassified virus Sulfolobus turreted icosahedral virus is known suggesting a common origin.
Examination of the pol genes that encode the DNA dependent DNA polymerase in various groups of viruses suggests a number of possible evolutionary relationships. All know viral DNA polymerases belong to the DNA pol families A and B. All possess a 3'-5'-exonuclease domain with three sequence motifs Exo I, Exo II and Exo III. The families A and B are distinguishable with family A Pol sharing 9 distinct consensus sequences and only two of them are convincingly homologous to sequence motif B of family B. The putative sequence motifs A, B, and C of the polymerase domain are located near the C-terminus in family A Pol and more central in family B Pol.
Phylogenetic analysis of these genes places the adenoviruses (Adenoviridae), bacteriophages (Caudovirales) and the plant and fungal linear plasmids into a single clade. A second clade includes the alpha- and delta-like viral Pol from insect ascovirus (Ascoviridae), mammalian herpesviruses (Herpesviridae), fish lymphocystis disease virus (Iridoviridae) and chlorella virus (Phycoviridae). The pol genes of the African swine fever virus (Asfarviridae), baculoviruses (Baculoviridae), fish herpesvirus (Herpesviridae), T-even bacteriophages (Myoviridae) and poxviruses (Poxviridae) were not clearly resolved. A second study showed that poxvirus, baculovirus and the animal herpesviruses form separate and distinct clades. Their relationship to the Asfarviridae and the Myoviridae was not examined and remains unclear.
The polymerases from the archaea are similar to family B DNA Pols. The T4-like viruses infect both bacteria and archaea and their pol gene resembles that of eukaryotes. The DNA polymerase of mitochondria resembles that of the T odd phages (Myoviridae).
ss DNA viruses
The evolutionary history of this group is currently poorly understood. An ancient origin for the single stranded circular DNA viruses has been proposed.
Capsid proteins of most icosahedral ssRNA and ssDNA viruses display the same structural fold, the eight-stranded beta-barrel, also known as the jelly-roll fold. On the other hand, the replication proteins of icosahedral ssDNA viruses belong to the superfamily of rolling-circle replication initiation proteins that are commonly found in prokaryotic plasmids. Based on these observations, it has been proposed that small DNA viruses have originated via recombination between RNA viruses and plasmids.
Given the similarities between the rep proteins of the alphasatellites and the nanoviruses, it is likely that the alphasatellites evolved from the nanoviruses. Further work in this area is needed to clarify this.
The geminiviruses may have evolved from phytoplasmal plasmids.
Based on the three-dimensional structure of the Rep proteins the geminiviruses and parvoviruses may be related.
The ancestor of the geminiviruses probably infected dicots.
The parvoviruses have frequently invaded the germ lines of diverse animal species including mammals, fishes, birds, tunicates, arthropods and flatworms. In particular they have been associated with the human genome for ~98 million years.
Since 1959 ~6300 prokaryote viruses have been described morphologically, including ~6200 bacterial and ~100 archaeal viruses. Archaeal viruses belong to 15 families and infect members of 16 archaeal genera. These are nearly exclusively hyperthermophiles or extreme halophiles. Tailed archaeal viruses are found only in the Euryarchaeota, whereas most filamentous and pleomorphic archaeal viruses occur in the Crenarchaeota. Bacterial viruses belong to 10 families and infect members of 179 bacterial genera: most these are members of the Firmicutes and γ-proteobacteria.
The vast majority (96.3%) are tailed with and only 230 (3.7%) are polyhedral, filamentous or pleomorphic. The family Siphoviridae is the largest family (>3600 descriptions: 57.3%). The tailed phages appear to be monophyletic and are the oldest known virus group. They arose repeatedly in different hosts and there are at least 11 separate lines of descent.
All of the known temperate phages employ one of only three different systems for their lysogenic cycle: lambda-like integration/excision, Mu-like transposition or the plasmid-like partitioning of phage N15.
A putative course of evolution of these phages has been proposed by Ackermann.
Tailed phages originated in the early Precambrian, long before eukaryotes and their viruses. The ancestral tailed phage had an icosahedral head of about 60 nanometers in diameter and a long non contractile tail with sixfold symmetry. The capsid contained a single molecule of double stranded DNA of about 50 kilobases. The tail was probably provided with a fixation apparatus. The head and tail were held together by a connector. The viral particle contained no lipids, was heavier than its descendant viruses and had a high DNA content proportional to its capsid size (~50%). Most of the genome coded for structural proteins. Morphopoietic genes clustered at one end of the genome, with head genes preceding tail genes. Lytic enzymes were probably coded for. Part of the phage genome was nonessential and possibly bacterial.
The virus infected its host from the outside and injected its DNA. Replication involved transcription in several waves and formation of DNA concatemers.
New phages were released by burst of the infected cell after lysis of host membranes by a peptidoglycan hydrolase. Capsids were assembled from a starting point, the connector and around a scaffold. They underwent an elaborate maturation process involving protein cleavage and capsid expansion. Heads and tails were assembled separately and joined later. The DNA was cut to size and entered preformed capsids by a headful mechanism.
The asfarviruses, iridoviruses, mimiviruses, phycodnaviruses and poxviruses have been shown to belong to a single group, – the large nuclear and cytoplasmic DNA viruses. These are also abbreviated "NCLDV". This clade can be divided into two groups:
- the iridoviruses-phycodnaviruses-mimiviruses group. The phycodnaviruses and mimiviruses are sister clades.
- the poxvirus-asfarviruses group.
It is probable that these viruses evolved before the separation of eukaryoyes into the extant crown groups. The ancestral genome was complex with at least 41 genes including (1) the replication machinery (2) up to four RNA polymerase subunits (3) at least three transcription factors (4) capping and polyadenylation enzymes (5) the DNA packaging apparatus (6) and structural components of an icosahedral capsid and the viral membrane.
The evolution of this group of viruses appears to be complex with genes having been gained from multiple sources.
Another group of large viruses — the Pandoraviridae — has been described. Two species — Pandoravirus salinus and Pandoravirus dulcis — have been recognized. These were isolated from Chile and Australia respectively. These viruses are about one micrometer in diameter making them one of the largest viruses discovered so far. Their gene complement is larger than any other known virus to date. At present they appear to be unrelated to any other species of virus.
- Colson P, de Lamballerie X, Fournous G, Raoult D (2012). "Reclassification of giant viruses composing a fourth domain of life in the new order Megavirales". Intervirology 55 (5): 321–32. doi:10.1159/000336562. PMID 22508375.
- Simoliūnas E, Kaliniene L, Truncaitė L, Zajančkauskaitė A, Staniulis J, Kaupinis A, Ger M, Valius M, Meškys R, et al. (2013). "Klebsiella phage vB_KleM-RaK2 — A giant singleton virus of the family Myoviridae". PLoS ONE 8 (4): e60717. doi:10.1371/journal.pone.0060717. PMC 3622015. PMID 23593293.
- Pietilä MK, Atanasova NS, Manole V, Liljeroos L, Butcher SJ, Oksanen HM, Bamford DH (2012). "Virion Architecture Unifies Globally Distributed Pleolipoviruses Infecting Halophilic Archaea". Journal of Virology 86 (9): 5067–79. doi:10.1128/JVI.06915-11. PMC 3347350. PMID 22357279.
- Sencilo A, Paulin L, Kellner S, Helm M, Roine E (2012). "Related haloarchaeal pleomorphic viruses contain different genome types". Nucleic Acids Res 40 (12): 5523–34. doi:10.1093/nar/gks215. PMC 3384331. PMID 22396526.
- Pietilä MK, Atanasova NS, Manole V, Liljeroos L, Butcher SJ, Oksanen HM, Bamford DH (2012). "Virion architecture unifies globally distributed pleolipoviruses infecting halophilic archaea". J Virol 86 (9): 5067–79. doi:10.1128/JVI.06915-11. PMC 3347350. PMID 22357279.
- Sinshemer RL (1959). "Purification and properties of bacteriophage φX174". Journal of Molecular Biology 1: 37. doi:10.1016/S0022-2836(59)80005-X.
- Sinshemer RL (1959). "A single-stranded deoxyribonucleic acid from bacteriophage φX174". Journal of Molecular Biology 1: 43. doi:10.1016/S0022-2836(59)80006-1.
- Desnues C, Rodriguez-Brito B, Rayhawk S, Kelley S, Tran T, Haynes M, Liu H, Furlan M, Wegley L, Chau B, Ruan Y, Hall D, Angly FE, Edwards RA, Li L, Thurber RV, Reid RP, Siefert J, Souza V, Valentine DL, Swan BK, Breitbart M, Rohwer F (2008). "Biodiversity and biogeography of phages in modern stromatolites and thrombolites". Nature 452 (7185): 340–3. doi:10.1038/nature06735. PMID 18311127.
- Angly FE, Felts B, Breitbart M, Salamon P, Edwards RA, Carlson C, Chan AM, Haynes M, Kelley S, Liu H, Mahaffy JM, Mueller JE, Nulton J, Olson R, Parsons R, Rayhawk S, Suttle CA, Rohwer F (2006). "The marine viromes of four oceanic regions". PLoS Biol 4 (11): e368. doi:10.1371/journal.pbio.0040368. PMC 1634881. PMID 17090214.
- Roux S, Krupovic M, Poulet A, Debroas D, Enault F (2012). "Evolution and diversity of the Microviridae viral family through a collection of 81 new complete genomes assembled from virome reads". PLoS ONE 7 (7): e40418. doi:10.1371/journal.pone.0040418. PMC 3394797. PMID 22808158.
- Rosario K, Duffy S, Breitbart M (2009). "Diverse circovirus-like genome architectures revealed by environmental metagenomics". J Gen Virol. 90 (Pt 10): 2418–24. doi:10.1099/vir.0.012955-0. PMID 19570956.
- Tijssen P, Bergoin M (1995). "Densonucleosis viruses constitute an increasingly diversified subfamily among the parvoviruses". Seminars in Virology 6 (5): 347–355. doi:10.1006/smvy.1995.0041.
- Sukhumsirichart W, Attasart P, Boonsaeng V, Panyim S (2006). "Complete nucleotide sequence and genomic organization of hepatopancreatic parvovirus (HPV) of Penaeus monodon". Virology 346 (2): 266–277. doi:10.1016/j.virol.2005.06.052. PMID 16356523.
- Kim HK, Park SJ, Nguyen VG, Song DS, Moon HJ, Kang BK, Park BK (2011). "Identification of a novel single stranded circular DNA virus from bovine stool". J Gen Virol 93 (Pt 3): 635–9. doi:10.1099/vir.0.037838-0. PMID 22071514.
- Sikorski A, Argüello-Astorga GR, Dayaram A, Dobson RC, Varsani A (2012). "Discovery of a novel circular single-stranded DNA virus from porcine faeces". Arch Virol 158 (1): 283–9. doi:10.1007/s00705-012-1470-0. PMID 22972681.
- Rosario K, Dayaram A, Marinov M, Ware J, Kraberger S, Stainton D, Breitbart M, Varsani A (2012). "Diverse circular ssDNA viruses discovered in dragonflies (Odonata: Epiprocta)". J Gen Virol 93 (12): 2668–2681. doi:10.1099/vir.0.045948-0. PMID 22915694.
- Kim AR, Chung HC, Kim HK, Kim EO, Nguyen VG, Choi MG, Yang HJ, Kim JA, Park BK (February 2014). "Characterization of a complete genome of a circular single-stranded DNA virus from porcine stools in Korea". Virus Genes 48 (1): 81–8. doi:10.1007/s11262-013-1003-2. PMID 24170425.
- Sikorski A, Kearvell J, Elkington S, Dayaram A, Argüello-Astorga GR, Varsani A (2013). "Novel ssDNA viruses discovered in yellow-crowned parakeet (Cyanoramphus auriceps) nesting material". Arch Virol 158 (7): 1603–7. doi:10.1007/s00705-013-1642-6. PMID 23417396.
- Reuter G, Boros A, Delwart E, Pankovics P (2014). "Novel circular single-stranded DNA virus from turkey faeces". Arch Virol. doi:10.1007/s00705-014-2025-3. PMID 24562429.
- Phan TG, Vo NP, Bonkoungou IJ, Kapoor A, Barro N, O'Ryan M, Kapusinszky B, Wang C, Delwart E (2012). "Acute diarrhea in West-African children: diverse enteric viruses and a novel parvovirus genus". J Virol 86 (20): 11024–30. doi:10.1128/JVI.01427-12. PMC 3457132. PMID 22855485.
- Cheung AK, Ng TF, Lager KM, Alt DP, Delwart EL, Pogranichniy RM (2014) Unique circovirus-like genome detected in pig feces. Genome Announc 10: 2(2). pii: e00251-14. doi: 10.1128/genomeA.00251-14
- Castrignano SB, Nagasse-Sugahara TK, Kisielius JJ, Ueda-Ito M, Brandão PE, Curti SP (2013) Two novel circo-like viruses detected in human feces: complete genome sequencing and electron microscopy analysis. Virus Res 178(2):364-73. doi: 10.1016/j.virusres.2013.09.018
- Yoon HS, Price DC, Stepanauskas R, Rajah VD, Sieracki ME, Wilson WH, Yang EC, Duffy S, Bhattacharya D, et al. (2011). "Single-cell genomics reveals organismal interactions in uncultivated marine protists". Science 332 (6030): 714–7. doi:10.1126/science.1203163. PMID 21551060.
- Phan TG, Kapusinszky B, Wang C, Rose RK, Lipton HL, Delwart EL (2011). "The fecal viral flora of wild rodents". PLoS Pathog 7 (9): e1002218. doi:10.1371/journal.ppat.1002218. PMC 3164639. PMID 21909269.
- Bassami MR, Berryman D, Wilcox GE, Raidal SR (1998). "Psittacine beak and feather disease virus nucleotide sequence analysis and its relationship to porcine circovirus, plant circoviruses, and chicken anaemia virus". Virology 249 (2): 453–9. PMID 9791035.
- Ng TF, Manire C, Borrowman K, Langer T, Ehrhart L, Breitbart M (2009). "Discovery of a novel single-stranded DNA virus from a sea turtle fibropapilloma by using viral metagenomics". J Virol 83 (6): 2500–9. doi:10.1128/JVI.01946-08. PMC 2648252. PMID 19116258.
- Pham HT, Bergoin M, Tijssen P (2013). "Acheta domesticus volvovirus, a novel single-stranded circular DNA virus of the house cricket". Genome Announc 1 (2): e0007913. doi:10.1128/genomeA.00079-13.
- Dayaram A, Goldstien S, Zawar-Reza P, Gomez C, Harding JS, Varsani A (2013). "whose replication associated protein (Rep) shares similarities with Rep-like sequences of bacterial origin". J Gen Virol. doi:10.1099/vir.0.050088-0. PMID 23364192.
- Rebrikov DV, Bulina ME, Bogdanova EA, Vagner LL, Lukyanov SA (2002). "Complete genome sequence of a novel extrachromosomal virus-like element identified in planarian Girardia tigrina". BMC Genomics 13: 15. doi:10.1186/1471-2164-3-15. PMC 3269984. PMID 22233149.
- Ng TF, Alavandi S, Varsani A, Burghart S, Breitbart M (2013). "Metagenomic identification of a nodavirus and a circular ssDNA virus in semi-purified viral nucleic acids from the hepatopancreas of healthy Farfantepenaeus duorarum shrimp". Dis Aquat Organ 105 (3): 237–42. doi:10.3354/dao02628. PMID 23999707.
- Pham HT, Yu Q, Boisvert M, Van HT, Bergoin M, Tijssen P (2014). "A circo-like virus isolated from Penaeus monodon shrimps". Genome Announc 2 (1): e01172–13. doi:10.1128/genomeA.01172-13. PMC 3894284. PMID 24435870.
- Dayaram A, Galatowitsch M, Harding JS, Argüello-Astorga GR, Varsani A (March 2014). "Novel circular DNA viruses identified in Procorduliagrayi and Xanthocnemiszealandica larvae using metagenomic approaches". Infect Genet Evol 22: 134–41. doi:10.1016/j.meegid.2014.01.013. PMID 24462907.
- Yu X, Li B, Fu Y, Jiang D, Ghabrial SA, Li G, Peng Y, Xie J, Cheng J, Huang J, Yi X (2010). "A geminivirus-related DNA mycovirus that confers hypovirulence to a plant pathogenic fungus". Proc Natl Acad Sci USA 107 (18): 8387–92. doi:10.1073/pnas.0913535107. PMC 2889581. PMID 20404139.
- van den Brand JM, van Leeuwen M, Schapendonk CM, Simon JH, Haagmans BL, Osterhaus AD, Smits SL (2012). "Metagenomic Analysis of the Viral Flora of Pine Marten and European Badger Feces". Journal of Virology 86 (4): 2360–5. doi:10.1128/JVI.06373-11. PMC 3302375. PMID 22171250.
- Dayaram A, Opong A, Jäschke A, Hadfield J, Baschiera M, Dobson RC, Offei SK, Shepherd DN, Martin DP, Varsani A (2012). "Molecular characterisation of a novel cassava associated circular ssDNA virus". Virus Res 166 (1–2): 130–5. doi:10.1016/j.virusres.2012.03.009. PMID 22465471.
- Krenz B, Thompson JR, Fuchs M, Perry KL (2012). "Complete genome sequence of a new circular DNA virus from grapevine". J Virol 86 (14): 7715. doi:10.1128/JVI.00943-12. PMC 3416304. PMID 22733880.
- Al Rwahnih M, Dave A, Anderson MM, Rowhani A, Uyemoto JK, Sudarshana M (October 2013). "Association of a DNA virus with grapevines affected by red blotch disease in California". Phytopathology Phytopathology 103 (10): 1069–76. doi:10.1094/PHYTO-10-12-0253-R. PMID 23656312.
- Bernardo P, Golden M, Akram M, et al. (October 2013). "Identification and characterisation of a highly divergent geminivirus: evolutionary and taxonomic implications". Virus Res. 177 (1): 35–45. doi:10.1016/j.virusres.2013.07.006. PMID 23886668.
- Pietilä MK, Laurinavicius S, Sund J, Roine E, Bamford DH (2010). "The single-stranded DNA genome of novel archaeal virus Halorubrum pleomorphic virus 1 is enclosed in the envelope decorated with glycoprotein spikes". J Virol 84 (2): 788–798. doi:10.1128/JVI.01347-09. PMC 2798366. PMID 19864380.
- Mochizuki T, Krupovic M, Pehau-Arnaudet G, Sako Y, Forterre P, Prangishvili D (2012). "Archaeal virus with exceptional virion architecture and the largest single-stranded DNA genome". Proc Natl Acad Sci U S A 109 (33): 13386–91. doi:10.1073/pnas.1203668109. PMC 3421227. PMID 22826255.
- Labonté JM, Suttle CA (November 2013). "Previously unknown and highly divergent ssDNA viruses populate the oceans". ISME J 7 (11): 2169–77. doi:10.1038/ismej.2013.110. PMID 23842650.
- Diemer GS, Stedman KM (2012). "A novel virus genome discovered in an extreme environment suggests recombination between unrelated groups of RNA and DNA viruses". Biology Direct 7: 13. doi:10.1186/1745-6150-7-13. PMC 3372434. PMID 22515485.
- Roux S, Enault F, Bronner G, Vaulot D, Forterre P, Krupovic M (2013). "Chimeric viruses blur the borders between the major groups of eukaryotic single-stranded DNA viruses". Nat Commun 4: 2700. doi:10.1038/ncomms3700. PMID 24193254.
- Tomaru Y, Toyoda K, Suzuki H, Nagumo T, Kimura K, Takao Y (2013). "New single-stranded DNA virus with a unique genomic structure that infects marine diatom Chaetoceros setoensis". Sci Rep 3: 3337. doi:10.1038/srep03337. PMC 3840382. PMID 24275766.
- McGeoch DJ, Rixon FJ, Davison AJ (2006). "Topics in herpesvirus genomics and evolution". Virus Res 117 (1): 90–104. doi:10.1016/j.virusres.2006.01.002. PMID 16490275.
- Davison AJ (2010). "Herpesvirus systematics". Vet Microbiol 143 (1-2): 52–69. doi:10.1016/j.vetmic.2010.02.014. PMC 2995426. PMID 20346601.
- Grose C (2012). "Pangaea and the Out-of-Africa Model of Varicella-Zoster Virus Evolution and Phylogeography". Journal of Virology 86 (18): 9558–65. doi:10.1128/JVI.00357-12. PMC 3446551. PMID 22761371.
- McGeoch DJ, Cook S, Dolan A, Jamieson FE, Telford EA (1995). "Molecular phylogeny and evolutionary timescale for the family of mammalian herpesviruses". J Mol Biol 247 (3): 443–458. doi:10.1006/jmbi.1995.0152. PMID 7714900.
- McGeoch DJ, Cook S (1994). "Molecular phylogeny of the alphaherpesvirinae subfamily and a proposed evolutionary timescale". J Mol Biol 238 (1): 9–22. doi:10.1006/jmbi.1994.1264. PMID 8145260.
- Davison AJ (2002). "Evolution of the herpesviruses". Veterinary microbiology 86 (1–2): 69–88. doi:10.1016/S0378-1135(01)00492-8. PMID 11888691.
- Baker ML, Jiang W, Rixon FJ, Chiu W (2005). "Common ancestry of herpesviruses and tailed DNA bacteriophages". J. Virol. 79 (23): 14967–70. doi:10.1128/JVI.79.23.14967-14970.2005. PMC 1287596. PMID 16282496.
- Federici BA, Bideshi DK, Tan Y, Spears T, Bigot Y (2009). "Ascoviruses: superb manipulators of apoptosis for viral replication and transmission". Curr Top Microbiol Immunol. Current Topics in Microbiology and Immunology 328: 171–196. doi:10.1007/978-3-540-68618-7_5. ISBN 978-3-540-68617-0. PMID 19216438.
- Wilson WH, Van Etten JL, Allen MJ (2009). "The Phycodnaviridae: the story of how tiny giants rule the world". Curr Top Microbiol Immunol. Current Topics in Microbiology and Immunology 328: 1–42. doi:10.1007/978-3-540-68618-7_1. ISBN 978-3-540-68617-0. PMC 2908299. PMID 19216434.
- Prangishvili D, Garrett RA (2004). "Exceptionally diverse morphotypes and genomes of crenarchaeal hyperthermophilic viruses". Biochem Soc Trans 32 (Pt 2): 204–8. doi:10.1042/BST0320204. PMID 15046572.
- Ogata H, Toyoda K, Tomaru Y, Nakayama N, Shirai Y, Claverie JM, Nagasaki K (2009). "Remarkable sequence similarity between the dinoflagellate-infecting marine girus and the terrestrial pathogen African swine fever virus". Virol J 6: 178. doi:10.1186/1743-422X-6-178. PMC 2777158. PMID 19860921.
- Krupovic M, Bamford DH (2008). "Virus evolution: how far does the double beta-barrel viral lineage extend?". Nature Reviews Microbiology 6 (12): 941–8. doi:10.1038/nrmicro2033. PMID 19008892.
- Benson SD, Bamford JK, Bamford DH, Burnett RM (1999). "Viral evolution revealed by bacteriophage PRD1 and human adenovirus coat protein structures". Cell 98 (6): 825–833. doi:10.1016/S0092-8674(00)81516-0. PMID 10499799.
- Thézé J, Bézier A, Periquet G, Drezen JM, Herniou EA (2011). "Paleozoic origin of insect large dsDNA viruses". Proc Natl Acad Sci USA 108 (38): 15931–5. doi:10.1073/pnas.1105580108. PMC 3179036. PMID 21911395.
- Jehle JA, Abd-Alla AM, Wang Y (2012). "Phylogeny and evolution of Hytrosaviridae". J Invertebr Pathol. 112 Suppl: S62–7. doi:10.1016/j.jip.2012.07.015. PMID 22841640.
- Wang Y, Bininda-Emonds OR, van Oers MM, Vlak JM, Jehle JA (2011). "The genome of Oryctes rhinoceros nudivirus provides novel insight into the evolution of nuclear arthropod-specific large circular double-stranded DNA viruses". Virus Genes. 42 (3): 444–456. doi:10.1007/s11262-011-0589-5. PMID 21380757.
- Bézier A, Annaheim M, Herbinière J, Wetterwald C, Gyapay G, Bernard-Samain S, Wincker P, Roditi I, Heller M, Belghazi M, Pfister-Wilhem R, Periquet G, Dupuy C, Huguet E, Volkoff AN, Lanzrein B, Drezen JM (2009). "Polydnaviruses of braconid wasps derive from an ancestral nudivirus". Science 323 (5916): 926–930. doi:10.1126/science.1166788. PMID 19213916.
- Keller J, Leulliot N, Cambillau C, Campanacci V, Porciero S, Prangishvilli D, Forterre P, Cortez D, Quevillon-Cheruel S, van Tilbeurgh H (2007). "Crystal structure of AFV3-109, a highly conserved protein from crenarchaeal viruses". Virol J 22 (4): 12. doi:10.1186/1743-422X-4-12. PMC 1796864. PMID 17241456.
- Knopf CW (1998). "Evolution of viral DNA-dependent DNA polymerases". Virus Genes 16 (1): 47–58. doi:10.1023/A:1007997609122. PMID 9562890.
- Villarreal LP, DeFilippis VR (2000). "A hypothesis for DNA viruses as the origin of eukaryotic replication proteins". J Virol 74 (15): 7079–84. doi:10.1128/JVI.74.15.7079-7084.2000. PMC 112226. PMID 10888648.
- Zillig W, Prangishvilli D, Schleper C, Elferink M, Holz I, Albers S, Janekovic D, Götz D (1996). "Viruses, plasmids and other genetic elements of thermophilic and hyperthermophilic Archaea". FEMS Microbiol Rev 18 (2–3): 225–236. doi:10.1111/j.1574-6976.1996.tb00239.x. PMID 8639330.
- Shutt TE, Gray MW (2005). "Bacteriophage origins of mitochondrial replication and transcription proteins". Trends Genet 22 (2): 90–95. doi:10.1016/j.tig.2005.11.007. PMID 16364493.
- Yutin N, Raoult D, Koonin EV (2013). "Virophages, polintons, and transpovirons: a complex evolutionary network of diverse selfish genetic elements with different reproduction strategies". Virol J 10 (1): 158. doi:10.1186/1743-422X-10-158. PMC 3671162. PMID 23701946.
- Delwart E, Li L (2012). Rapidly expanding genetic diversity and host range of the Circoviridae viral family and other Rep encoding small circular ssDNA genomes. Virus Res 164 (1–2). pp. 114–121. doi:10.1016/j.virusres.2011.11.021. PMC 3289258. PMID 22155583.
- Ilyina TV, Koonin EV (1992). "Conserved sequence motifs in the initiator proteins for rolling circle DNA replication encoded by diverse replicons from eubacteria, eucaryotes and archaebacteria". Nucleic Acids Res 20 (13): 3279–85. doi:10.1093/nar/20.13.3279. PMC 312478. PMID 1630899.
- Krupovic M (2012). "Recombination between RNA viruses and plasmids might have played a central role in the origin and evolution of small DNA viruses". BioEssays 34 (10): 867–870. doi:10.1002/bies.201200083. PMID 22886750.
- Krupovic M (2013). "Networks of evolutionary interactions underlying the polyphyletic origin of ssDNA viruses". Curr Opin Virol 3 (5): 578–586. doi:10.1016/j.coviro.2013.06.010. PMID 23850154.
- Gibbs MJ, Weiller GF (1999). "Evidence that a plant virus switched hosts to infect a vertebrate and then recombined with a vertebrate-infecting virus". Proc Natl Acad Sci USA 96 (14): 8022–7. doi:10.1073/pnas.96.14.8022. PMC 22181. PMID 10393941.
- Meehan BM, Creelan JL, McNulty MS, Todd D (1997). "Sequence of porcine circovirus DNA: affinities with plant circoviruses". J Gen Virol 78 (Pt 1): 221–7. PMID 9010307.
- Niagro FD, Forsthoefel AN, Lawther RP, Kamalanathan L, Ritchie BW, Latimer KS, Lukert PD (1998). "Beak and feather disease virus and porcine circovirus genomes: intermediates between the geminiviruses and plant circoviruses". Arch Virol 143 (9): 1723–44. doi:10.1007/s007050050412. PMID 9787657.
- Xie Y, Wu P, Liu P, Gong H, Zhou X (2010). "Characterization of alphasatellites associated with monopartite begomovirus/betasatellite complexes in Yunnan, China". Virol J 7: 178. doi:10.1186/1743-422X-7-178. PMC 2922188. PMID 20678232.
- Krupovic M, Ravantti JJ, Bamford DH (2009). "Geminiviruses: a tale of a plasmid becoming a virus" (PDF). BMC Evol Biol 9: 112. doi:10.1186/1471-2148-9-112. PMC 2702318. PMID 19460138.
- Gronenborn B (2004). "Nanoviruses: genome organisation and protein function". Vet Microbiol 98 (2): 103–9. doi:10.1016/j.vetmic.2003.10.015. PMID 14741122.
- Belyi VA, Levine AJ, Skalka AM (2010). "Sequences from ancestral single-stranded DNA viruses in vertebrate genomes: the parvoviridae and circoviridae are more than 40 to 50 million years old". J Virol 84 (23): 12458–62. doi:10.1128/JVI.01789-10. PMC 2976387. PMID 20861255.
- Liu H, Fu Y, Xie J, Cheng J, Ghabrial SA, Li G, Peng Y, Yi X, Jiang D. (2011). "Widespread endogenization of Densoviruses and Parvoviruses in animal and human genomes". J Virol 85 (19): 9863–76. doi:10.1128/JVI.00828-11. PMC 3196449. PMID 21795360.
- Ackermann HW, Prangishvili D (2012). "Prokaryote viruses studied by electron microscopy". Arch Virol 157 (10): 1843–9. doi:10.1007/s00705-012-1383-y. PMID 22752841.
- Ackermann HW (2003). "Bacteriophage observations and evolution". Res Microbiol 154 (4): 245–251. doi:10.1016/S0923-2508(03)00067-6. PMID 12798228.
- Ackermann HW (1998). "Tailed bacteriophages: the order caudovirales". Adv Virus Res. Advances in Virus Research 51: 135–201. doi:10.1016/S0065-3527(08)60785-X. ISBN 9780120398515. PMID 9891587.
- Iyer LM, Balaji S, Koonin EV, Aravind L (2006). "Evolutionary genomics of nucleo-cytoplasmic large DNA viruses". Virus Res. 117 (1): 156–184. doi:10.1016/j.virusres.2006.01.009. PMID 16494962.
- Yutin N, Wolf YI, Raoult D, Koonin EV (2009). "Eukaryotic large nucleo-cytoplasmic DNA viruses: clusters of orthologous genes and reconstruction of viral genome evolution". Virol. J. 6: 223. doi:10.1186/1743-422X-6-223. PMC 2806869. PMID 20017929.
- Yutin N, Koonin EV (2012). "Hidden evolutionary complexity of Nucleo-Cytoplasmic Large DNA viruses of eukaryotes". Virol J 9 (1): 161. doi:10.1186/1743-422X-9-161. PMC 3493329. PMID 22891861.
- Pennisi, E. (2013). "Ever-Bigger Viruses Shake Tree of Life". Science 341 (6143): 226–7. doi:10.1126/science.341.6143.226. PMID 23868995.
- Legendre, M.; Bartoli, J.; Shmakova, L.; Jeudy, S.; Labadie, K.; Adrait, A.; Lescot, M.; Poirot, O.; Bertaux, L.; Bruley, C.; Coute, Y.; Rivkina, E.; Abergel, C.; Claverie, J.-M. (2014). "Thirty-thousand-year-old distant relative of giant icosahedral DNA viruses with a pandoravirus morphology". Proc. Natl. Acad. Sci. U.S.A. To appear (11): 4274. doi:10.1073/pnas.1320670111. PMID 24591590.
- Fauquent, C. M.; Mayo, M. A.; Maniloff, J.; Desselberger, U.; Ball, L. A.; eds. (2005-05-27). "8th Reports of the International Committee on Taxonomy of Viruses". Academic Press. U.S. National Center for Biotechnology Information, National Library for Medicine, National Institutes of Health.