Caudovirales
   HOME

TheInfoList



OR:

''Caudovirales'' is an order of
virus 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. Since Dmitri Ivanovsky's 1 ...
es known as the tailed
bacteriophage A bacteriophage (), also known informally as a ''phage'' (), is a duplodnaviria virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν ('), meaning "to devour". Bacteri ...
s (''cauda'' is Latin for "tail"). Under the
Baltimore classification Baltimore classification is a system used to classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behave similarly as a di ...
scheme, the ''Caudovirales'' are group I viruses as they have double stranded DNA (dsDNA) genomes, which can be anywhere from 18,000 base pairs to 500,000 base pairs in length. The virus particles have a distinct shape; each virion has an
icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...
head that contains the viral genome, and is attached to a flexible tail by a connector protein. The order encompasses a wide range of viruses, many containing genes of similar nucleotide sequence and function. However, some tailed bacteriophage genomes can vary quite significantly in nucleotide sequence, even among the same genus. Due to their characteristic structure and possession of potentially homologous genes, it is believed these bacteriophages possess a common origin. There are 14 families, 73 subfamilies, 927 genera, and 2,814 species in the order. This makes ''Caudovirales'' the most populous order among viruses, accounting for approximately 30% of all recognized virus species and nearly half of all virus genera.


Infection

Upon encountering a host bacterium, the tail section of the virion binds to
receptors Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a n ...
on the cell surface and delivers the DNA into the cell by use of an injectisome-like mechanism (an injectisome is a nanomachine that evolved for the delivery of proteins by type III secretion). The tail section of the virus punches a hole through the bacterial cell wall and plasma membrane and the genome passes down the tail into the cell. Once inside the genes are expressed from transcripts made by the host machinery, using host
ribosome Ribosomes ( ) are macromolecular machines, found within all cells, that perform biological protein synthesis (mRNA translation). Ribosomes link amino acids together in the order specified by the codons of messenger RNA (mRNA) molecules to ...
s. Typically, the genome is replicated by use of
concatemer A concatemer is a long continuous DNA molecule that contains multiple copies of the same DNA sequence linked in series. These polymeric molecules are usually copies of an entire genome linked end to end and separated by ''cos'' sites (a protein bi ...
s, in which overlapping segments of DNA are made, and then put together to form the whole genome.


Assembly and maturation

Viral
capsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may ...
proteins come together to form a precursor
prohead A prohead or procapsid is an immature viral capsid structure formed in the early stages of self-assembly of some bacteriophages, including the ''Caudovirales ''Caudovirales'' is an order of viruses known as the tailed bacteriophages (''cauda' ...
, into which the genome enters. Once this has occurred, the prohead undergoes maturation by cleavage of capsid subunits to form an icosahedral
phage A bacteriophage (), also known informally as a ''phage'' (), is a duplodnaviria virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν ('), meaning "to devour". Bacterio ...
head with 5-fold symmetry. After the head maturation, the tail is joined in one of two ways: Either the tail is constructed separately, and joined with the connector, or the tail is constructed directly onto the phage head. The tails consist of helix based proteins with 6-fold symmetry. After maturation of virus particles, the cell is lysed by
lysin Lysins, also known as endolysins or murein hydrolases, are hydrolytic enzymes produced by bacteriophages in order to cleave the host's cell wall during the final stage of the lytic cycle. Lysins are highly evolved enzymes that are able to target ...
s, holins, or a combination of the two.


Taxonomy

Because of the lack of homology between the amino acid and DNA sequences of these viruses these factors are precluded from being used as taxonomic markers as is common for other organisms, the three families discussed below (''
Myoviridae ''Myoviridae'' is a family of bacteriophages in the order ''Caudovirales''. Bacteria and archaea serve as natural hosts. There are 625 species in this family, assigned to eight subfamilies and 217 genera. Subdivisions The subfamily ''Tevenvirinae ...
'', ''
Podoviridae ''Podoviridae'' is a family of bacteriophage in the order ''Caudovirales'' often associated with T-7 like phages. There are 130 species in this family, assigned to 3 subfamilies and 52 genera. This family is characterized by having very short, n ...
'', and ''
Siphoviridae ''Siphoviridae'' is a family of double-stranded DNA viruses in the order ''Caudovirales''. Bacteria and archaea serve as natural hosts. There are 1,166 species in this family, assigned to 366 genera and 22 subfamilies. The characteristic structu ...
'') are defined on the basis of
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
. This classification scheme was originated by Bradley in 1969 and has been extended since. All viruses in this order have icosahedral or oblate heads but differ in the length and contractile abilities of their tails. The ''Myoviridae'' have long tails that are contractile; the ''Podoviridae'' have short noncontractile tails; and the ''Siphoviridae'' have long noncontractile tails. ''Siphoviridae'' constitute the majority of the known tailed viruses. Bradley referred to what is now known as the ''Myoviridae'' as type A, ''Siphoviridae'' as type B, and the ''Podoviridae'' as type C. He also divided his groups on the basis of head morphology: Within group A, A1 have small isometric heads; A2 have prolate heads; and A3 have elongated heads. Within groups B and C, numbers were similarly assigned: B1 and C1 have small isometric heads; B2 and C2 have prolate heads; and B3 and C3 have elongated heads. In addition the aforementioned three families, a total of 14 families and one ''
incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...
'' genus are assigned to the order: * ''
Ackermannviridae ''Ackermannviridae'' is a family of viruses in the order ''Caudovirales''. Gammaproteobacteria in the phylum Pseudomonadota serve as natural hosts. There are 2 subfamilies, 10 genera, and 63 species in the family. Etymology The family's name, ' ...
'' * ''
Autographiviridae ''Autographiviridae'' is a family of viruses in the order ''Caudovirales''. Bacteria serve as natural hosts. There are 373 species in this family, assigned to 9 subfamilies and 133 genera. History Since the 1990s, the term "T7 supergroup" has be ...
'' * '' Chaseviridae'' * '' Demerecviridae'' * '' Drexlerviridae'' * '' Guelinviridae'' * ''
Herelleviridae ''Herelleviridae'' is a family of bacterial viruses of the order ''Caudovirales'' infecting members of the phylum Firmicutes. The family has five subfamilies, 33 genera and 92 species. __TOC__ Etymology The family's name, ''Herelle'' is in hono ...
'' * ''
Myoviridae ''Myoviridae'' is a family of bacteriophages in the order ''Caudovirales''. Bacteria and archaea serve as natural hosts. There are 625 species in this family, assigned to eight subfamilies and 217 genera. Subdivisions The subfamily ''Tevenvirinae ...
'' * ''
Podoviridae ''Podoviridae'' is a family of bacteriophage in the order ''Caudovirales'' often associated with T-7 like phages. There are 130 species in this family, assigned to 3 subfamilies and 52 genera. This family is characterized by having very short, n ...
'' * '' Rountreeviridae'' * '' Salasmaviridae'' * '' Schitoviridae'' * ''
Siphoviridae ''Siphoviridae'' is a family of double-stranded DNA viruses in the order ''Caudovirales''. Bacteria and archaea serve as natural hosts. There are 1,166 species in this family, assigned to 366 genera and 22 subfamilies. The characteristic structu ...
'' * '' Zobellviridae'' * '' Lilyvirus'', the unassigned genus


Bacteriophage evolution

Bacteriophages occur in over 195 bacterial or archaeal genera. They arose repeatedly in different hosts and there are at least 11 separate lines of descent. Over 6300 bacteriophages have been examined in the electron microscope since 1959. Of these, more than 96 percent have tails. Of the tailed phages, about 57 percent have long, noncontractile tails (''Siphoviridae''). Tailed phages appear to be monophyletic and are the oldest known virus group.


See also

* WO virus


References


Further reading

* * {{Taxonbar, from=Q6521 Archaeal viruses Bacteriophages Virus orders