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, herpes, and the chickenpox are caused by such DNA viruses.
An RNA virus is a virus that has RNA as its genetic material. This nucleic acid is usually single-stranded RNA (ssRNA) but may be double-stranded RNA (dsRNA). Notable human diseases caused by RNA viruses include Ebola virus disease, SARS, rabies, common cold, influenza, hepatitis C, hepatitis E, West Nile fever, polio and measles.
The Parvoviridae are a family of small, rugged, genetically-compact DNA viruses, known collectively as parvoviruses. There are currently >75 species in the family, divided among 13 genera and two subfamilies. Members of this family infect a wide array of animal hosts and have been divided into two subfamilies, which infect either vertebrates or invertebrates (Densovirinae).
Parvovirus is the common name applied to all the viruses in the Parvoviridae taxonomic family, although it can also be used specifically for members of one of the two Parvoviridae subfamilies, the Parvovirinae, which infect vertebrate hosts. Members of the second subfamily, the Densovirinae, which infect invertebrate hosts, are more commonly referred to as densoviruses. In subfamily Parvovirinae there are eight genera, containing a total of 58 recognized species, while in subfamily Densovirinae there are 5 genera and a total of 21 species. These viruses have small genomes, encoding just two genes, and must rely on the synthetic machinery of their host cell for their own preferential replication. This means that many parvoviruses require host cells to enter S-phase before viral DNA replication can initiate, but they do not encode any gene products that can drive this transition. Parvoviruses overcome this problem in various ways: viruses in many genera simply wait within the cell for it to enter S-phase under its own cell cycle control, which means that they can only infect actively-dividing cell populations. In contrast, the so-called adeno-associated viruses (AAVs) from genus Dependoparvovirus must wait until the cell is co-infected by a helper DNA virus, commonly an adenovirus or herpes virus, which does encode gene products that can drive the cell into S-phase, allowing AAV infection to initiate and out-compete the helper virus. A third strategy is used by human bocavirus 1 (HBoV1) from genus Bocaparvovirus, which appears to invoke a specific DNA-damage response in its host cell that ultimately supports viral DNA amplification and progeny virus production.
The Pseudoviridae are a family of viruses, including the following genera:
Tectiviridae is a family of viruses with three genera. Gram-negative bacteria serve as natural hosts. There are currently four species in this genus including the type species Enterobacteria phage PRD1. Tectiviruses have no head-tail structure, but are capable of producing tail-like tubes of ~ 60×10 nm upon adsorption or after chloroform treatment. The name is derived from Latin tectus.
The virus genus Ambidensovirus belongs to the Densovirinae subfamily of the family Parvoviridae. Members of this genus are single-stranded DNA viruses. This genus infects invertebrates, including insects, crustacea and echinoderms. There are currently eleven species in this genus including the type species Lepidopteran ambidensovirus 1.
The nucleocytoplasmic large DNA viruses(NCLDV), are an order of viruses that contain the Megavirales or giant viruses. There are nine families of nucleocytoplasmic large DNA viruses that all share certain genomic and structural characteristics; however, it is uncertain whether the similarities of the different families of this group have a common viral ancestor. One feature of this group is a large genome and the presence of many genes involved in DNA repair, DNA replication, transcription, and translation. Typically, viruses with smaller genomes do not contain genes for these processes. Most of the viruses in this family also replicate in both the host's nucleus and cytoplasm, thus the name nucleocytoplasmic.
Double-stranded (ds) RNA viruses are a diverse group of viruses that vary widely in host range, genome segment number and virion organization. Members of this group include the rotaviruses, known globally as a common cause of gastroenteritis in young children, and bluetongue virus, an economically important pathogen of cattle and sheep.
Rudivirus is a genus of viruses in the order Ligamenvirales; it is the only genus in the family Rudiviridae. These viruses are non-enveloped, stiff-rod-shaped viruses with linear dsDNA genomes, that infect hyperthermophilic archaea of the kingdom Crenarchaeota. There are currently three species in this genus including the type species Sulfolobus islandicus rod-shaped virus 2. The family name derives from the Latin rudis, thin rod, referring to the virion shape.
Lipothrixviridae is a family of viruses in the order Ligamenvirales. Thermophilic archaea in the kingdom Crenarchaeota serve as natural hosts. There are currently eight species in this family, divided among 3 genera.
Clavaviridae is a family of double-stranded viruses that infect archaea. This family was first described by the team led by D. Prangishvili in 2010. There is one genus in this family (Clavavirus). Within this genus, a single species has been described to date: Aeropyrum pernix bacilliform virus 1.
Bacilladnavirus is a genus of single stranded DNA viruses. Species in this genus infect diatoms. The name is derived from the phrase: ssDNA virus infecting Bacillariophytes. Although other single-stranded DNA viruses which infect diatoms have been discovered, the only species officially classified in this genus is Chaetoceros salsugineum DNA virus 01 (CsalDNAV01.) In addition, 4 genomes of uncultured bacilladnaviruses have been sequenced directly from environmental samples. It was suggested that the family Bacilladnaviridae be used to classify these viruses. This was accepted by the International Committee on Taxonomy of Viruses with its Master Species List (MSL) as of fall 2018.
A transpoviron is a mobile genetic element found in the genomes of giant DNA viruses.
Mastadenovirus is a genus of viruses, in the family Adenoviridae. Human, mammals, and vertebrates serve as natural hosts. There are currently 25 species in this genus, including the type species human mastadenovirus C. The genus as a whole includes many very common causes of human infection, estimated to be responsible for 2-5% of all respiratory infections, as well as gastrointestinal and eye infections. Symptoms are usually mild.
Amalgaviridae is a family of double-stranded RNA viruses that has one genus: Amalgavirus. Members of both the family and the genus are referred to as amalgaviruses. There are currently four recognized species of the family: Blueberry latent virus, Rhododendron virus A, Southern tomato virus, the type species of Amalgavirus, and Vicia cryptic virus M. The family and genus are called amalga, from amalgam, due to the viruses possessing characteristics of both partitiviruses and totiviruses, indicating a likely genetic relation to those two families. Members of this family infect plants and are transmitted vertically via seeds. Their genomes are monopartite, about 3.5 kilobases in length, and contain two partially overlapping open reading frames, encoding the RNA-dependent RNA polymerase (RdRp) and a putative capsid protein.
Alphatristromavirus is a genus of viruses in the family Tristomaviridae. The thermophilic archaebacterium Thermoproteus tenax serves as natural host. There are currently only two species in this genus: Thermoproteus tenax virus 1 and the type species Pyrobaculum filamentous virus 1The genus was formerly classified into family Lipothrixviridae of order Ligamenvirales.
Polintons are large DNA transposons which contain genes with homology to viral proteins and which are often found in eukaryotic genomes. They were first discovered in the mid-2000s and are the largest and most complex known DNA transposons. Polintons encode up to 10 individual proteins and derive their name from two key proteins, a DNA polymerase and a retroviral-like integrase.
The jelly roll or Swiss roll fold is a protein fold or supersecondary structure composed of eight beta strands arranged in two four-stranded sheets. The name of the structure was introduced by Jane S. Richardson in 1981, reflecting its resemblance to the jelly or Swiss roll cake. The fold is an elaboration on the Greek key motif and is sometimes considered a form of beta barrel. It is very common in viral proteins, particularly viral capsid proteins. Taken together, the jelly roll and Greek key structures comprise around 30% of the all-beta proteins annotated in the Structural Classification of Proteins (SCOP) database.
Ortervirales is an order that contains single-stranded RNA viruses that replicate through a DNA intermediate and double-stranded DNA viruses that replicate through an RNA intermediate . The name is derived from the reverse of retro.
