Viral evolution is a subfield of evolutionary biology and virology that is specifically concerned with the evolution of viruses. Viruses have short generation times, and many—in particular RNA viruses—have relatively high mutation rates. Although most viral mutations confer no benefit and often even prove deleterious to viruses, the rapid rate of viral mutation combined with natural selection allows viruses to quickly adapt to changes in their host environment. In addition, because viruses typically produce many copies in an infected host, mutated genes can be passed on to many offspring quickly. Although the chance of mutations and evolution can change depending on the type of virus, viruses overall have high chances for mutations.
Mimivirus is a genus of giant viruses, in the family Mimiviridae. Amoeba serve as their natural hosts. This genus contains a single identified species named Acanthamoeba polyphaga mimivirus (APMV). It also refers to a group of phylogenetically related large viruses.
Coccolithovirus is a genus of giant double-stranded DNA virus, in the family Phycodnaviridae. Algae, specifically Emiliania huxleyi, a species of coccolithophore, serve as natural hosts. There is only one described species in this genus: Emiliania huxleyi virus 86.
Bodo is a genus of microscopic kinetoplastids, flagellate excavates first described in 1831 by Christian Gottfried Ehrenberg. The genus is small, as it has recently been redefined to include only four species. Bodo includes free-living, phagotrophic organisms that can be found in many marine and freshwater environments as well as some terrestrial environments. Being phagotrophic, Bodo feeds on bacteria and other microorganisms that it finds while swimming through its water-based habitats. The swimming-like movement is facilitated by the two unequal flagella that Bodo possesses which arise from an anteriorly located flagellar pocket. Bodo is roughly bean-shaped and is often missed in samples from water or terrestrial environments due to its small size.
Bodo saltans is a free-living nonparasitic species of kinetoplastid flagellated phagotrophic protozoa that feed on bacteria. Bodo saltans cells have been reported in freshwater and marine environments.
Phycodnaviridae is a family of large (100–560 kb) double-stranded DNA viruses that infect marine or freshwater eukaryotic algae. Viruses within this family have a similar morphology, with an icosahedral capsid. As of 2014, there were 33 species in this family, divided among 6 genera. This family belongs to a super-group of large viruses known as nucleocytoplasmic large DNA viruses. Evidence was published in 2014 suggesting that specific strains of Phycodnaviridae might infect humans rather than just algal species, as was previously believed. Most genera under this family enter the host cell by cell receptor endocytosis and replicate in the nucleus. Phycodnaviridae play important ecological roles by regulating the growth and productivity of their algal hosts. Algal species such Heterosigma akashiwo and the genus Chrysochromulina can form dense blooms which can be damaging to fisheries, resulting in losses in the aquaculture industry. Heterosigma akashiwo virus (HaV) has been suggested for use as a microbial agent to prevent the recurrence of toxic red tides produced by this algal species. Phycodnaviridae cause death and lysis of freshwater and marine algal species, liberating organic carbon, nitrogen and phosphorus into the water, providing nutrients for the microbial loop.
Virophages are small, double-stranded DNA viral phages that require the co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant virus for their own replication. One of the characteristics of virophages is that they have a parasitic relationship with the co-infecting virus. Their dependence upon the giant virus for replication often results in the deactivation of the giant viruses. The virophage may improve the recovery and survival of the host organism.
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 11,000 of the millions of virus species have been described in detail. The study of viruses is known as virology, a subspeciality of microbiology.
Mimiviridae is a family of viruses. Amoeba and other protists serve as natural hosts. The family is divided in up to 4 subfamilies. Viruses in this family belong to the nucleocytoplasmic large DNA virus clade (NCLDV), also referred to as giant viruses.
Cafeteria roenbergensis virus (CroV) is a giant virus that infects the marine bicosoecid flagellate Cafeteria roenbergensis, a member of the microzooplankton community.
A giant virus, sometimes referred to as a girus, is a very large virus, some of which are larger than typical bacteria. All known giant viruses belong to the phylum Nucleocytoviricota.
Pandoravirus is a genus of giant virus, first discovered in 2013. It is the second largest in physical size of any known viral genus. Pandoraviruses have double stranded DNA genomes, with the largest genome size of any known viral genus.
Klosneuvirus is a new type of giant virus found by the analysis of low-complexity metagenomes from a wastewater treatment plant in Klosterneuburg, Austria. It has a 1.57-Mb genome coding unusually high number of genes typically found in cellular organisms, including aminoacyl transfer RNA synthetases with specificities for 19 different amino acids, over 10 translation factors and several tRNA-modifying enzymes. Klosneuvirus, Indivirus, Catovirus and Hokovirus, are part of a group of giant viruses denoted as Klosneuviruses or Klosneuvirinae, a proposed subfamily of the Mimiviridae.
Hokovirus (HokV) is a genus of giant double-stranded DNA-containing viruses (NCLDV). This genus was detected during the analysis of metagenome samples of bottom sediments of reservoirs at the wastewater treatment plant in Klosterneuburg, Austria. New Klosneuvirus (KNV), Catovirus and Indivirus genera were also described together with Hokovirus, building up a putative virus subfamily Klosneuvirinae (Klosneuviruses) with KNV as type genus. Hokovirus has a large genome of 1.33 million base pairs. This is the third largest genome among known Klosneuviruses after KNV and Catovirus. GC content is 21.4 % Classification of metagenome, made by analyzing 18S rRNA indicate that their hosts are relate to the simple Cercozoa.
Catovirus (CatV) is a genus of giant double-stranded DNA-containing viruses. This genus was detected during the analysis of metagenome samples of bottom sediments of reservoirs at the wastewater treatment plant in Klosterneuburg, Austria. New Klosneuvirus (KNV), Hokovirus and Indivirus genera were also described together with Catovirus, building up a putative virus subfamily Klosneuvirinae (Klosneuviruses) with KNV as type genus. Catovirus has a large genome of 1.53 million base pairs. This is the second largest genome among known Klosneuviruses after KNV. GC content is 26.4 % Classification of metagenome, made by analyzing 18S rRNA indicate that their hosts are relate to the simple Cercozoa.
Indivirus (IndV) is a genus of giant double-stranded DNA-containing viruses (NCLDV). This genus was detected during the analysis of metagenome samples of bottom sediments of reservoirs at the wastewater treatment plant in Klosterneuburg, Austria. New Klosneuvirus (KNV), Hokovirus and Catovirus genera were also described together with Indivirus, building up a putative virus subfamily Klosneuvirinae (Klosneuviruses) with KNV as type genus. Indivirus has a genome of 0.86 million base pairs. This is the smallest genome among Klosneuviruses as mentioned above. GC content is 26.6 % Classification of metagenome, made by analyzing 18S rRNA indicate that their hosts are relate to the simple Cercozoa.
Marine viruses are defined by their habitat as viruses that are found in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. Viruses are small infectious agents that can only replicate inside the living cells of a host organism, because they need the replication machinery of the host to do so. They can infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea.
Varidnaviria is a realm of viruses that includes all DNA viruses that encode major capsid proteins that contain a vertical jelly roll fold. The major capsid proteins (MCP) form into pseudohexameric subunits of the viral capsid, which stores the viral deoxyribonucleic acid (DNA), and are perpendicular, or vertical, to the surface of the capsid. Apart from this, viruses in the realm also share many other characteristics, such as minor capsid proteins (mCP) with the vertical jelly roll fold, an ATPase that packages viral DNA into the capsid, and a DNA polymerase that replicates the viral genome.
Nucleocytoviricota is a phylum of viruses. Members of the phylum are also known as the nucleocytoplasmic large DNA viruses (NCLDV), which serves as the basis of the name of the phylum with the suffix -viricota for virus phylum. These viruses are referred to as nucleocytoplasmic because they are often able to replicate in both the host's cell nucleus and cytoplasm.
Virosphere was coined to refer to all those places in which viruses are found or which are affected by viruses. However, more recently virosphere has also been used to refer to the pool of viruses that occurs in all hosts and all environments, as well as viruses associated with specific types of hosts, type of genome or ecological niche.
