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Caudovirales

Caudovirales

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Tailed bacteriophage structure: (1) head, (2) tail, (3) DNA, (4) capsid, (5) collar, (6) sheath, (7) tail fibres, (8) spikes, (9) base plate
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Illustrations of various Caudovirales. Not to scale.

Caudovirales is an order of viruses known as the tailed bacteriophages (cauda is Latin for "tail").[1] Under the Baltimore classification 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.[2] The virus particles have a distinct shape; each virion has an icosahedral head that contains the viral genome, and is attached to a flexible tail by a connector protein.[2] 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.[2]

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.[3]

Infection

Upon encountering a host bacterium, the tail section of the virion binds to receptors 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 ribosomes. Typically, the genome is replicated by use of concatemers, in which overlapping segments of DNA are made, and then put together to form the whole genome.[2]

Assembly and maturation

Viral capsid proteins come together to form a precursor prohead, into which the genome enters. Once this has occurred, the prohead undergoes maturation by cleavage of capsid subunits to form an icosahedral phage 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 lysins, holins, or a combination of the two.[2]

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, Podoviridae, and Siphoviridae) are defined on the basis of morphology. This classification scheme was originated by Bradley in 1969 and has been extended since.[2]

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.[4] Siphoviridae constitute the majority of the known tailed viruses.[2][5]

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 genus are assigned to the order:[3]

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.[5][6]

See also

References

  1. ^ Ackermann HW (1998). Tailed bacteriophages: the order caudovirales. Advances in Virus Research. Vol. 51. pp. 135–201. doi:10.1016/S0065-3527(08)60785-X. ISBN 9780120398515. PMC 7173057. PMID 9891587.
  2. ^ a b c d e f g "Double-Stranded DNA Bacteriophages". Boundless. 2017-11-11. Archived from the original on 2013-06-28.
  3. ^ a b "Virus Taxonomy: 2020 Release". International Committee on Taxonomy of Viruses (ICTV). March 2021. Retrieved 11 May 2021.
  4. ^ Maniloff J, Ackermann HW (1998). "Taxonomy of bacterial viruses: establishment of tailed virus genera and the order Caudovirales". Archives of Virology. 143 (10): 2051–63. doi:10.1007/s007050050442. PMID 9856093. S2CID 34921877.
  5. ^ a b Ackermann HW (May 2003). "Bacteriophage observations and evolution". Research in Microbiology. 154 (4): 245–51. doi:10.1016/S0923-2508(03)00067-6. PMID 12798228.
  6. ^ Ackermann HW, Prangishvili D (October 2012). "Prokaryote viruses studied by electron microscopy". Archives of Virology. 157 (10): 1843–9. doi:10.1007/s00705-012-1383-y. PMID 22752841. S2CID 16699662.
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Caudovirales: Brief Summary

provided by wikipedia EN
 src= Tailed bacteriophage structure: (1) head, (2) tail, (3) DNA, (4) capsid, (5) collar, (6) sheath, (7) tail fibres, (8) spikes, (9) base plate  src= Transmission electron micrograph of Gamma-Phage  src= Illustrations of various Caudovirales. Not to scale.

Caudovirales is an order of viruses known as the tailed bacteriophages (cauda is Latin for "tail"). Under the Baltimore classification 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 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.

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Caudovirales

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Structure du bactériophage à queue : (1) tête, (2) queue, (3) ADN, (4) capside, (5) collier, (6) gaine, (7) fibres constituant la queue, (8) spicules

Caudovirales est un ordre de virus connus sous le nom de bactériophages à queue (cauda signifie en latin « queue »)[1]. Selon la classification de Baltimore , Caudovirales est un ordre de virus du groupe I, leur génomes étant à ADN double brin (ADNds), qui peuvent avoir une longueur comprise entre 18 000 paires de bases et 500 000 paires de bases.[2] Les virions ont une forme distincte, chacun possédant une tête icosaédrique qui contient le génome viral et qui est attaché à une queue flexible à l'aide d'une protéine connectrice[2]. L'ordre englobe un large éventail de virus, dont la plupart contiennent des gènes de séquences nucléotidiques et de fonctions similaires. Cependant, certains génomes de bactériophages à queue peuvent varier de manière assez significative dans la séquence nucléotidique, et ce même au sein du même genre. En raison de leur structure caractéristique et de la possession de gènes potentiellement homologues, on pense que ces bactériophages possèdent une origine commune[2].

Cette ordre contient 14 familles, 73 sous-familles, 927 genres et 2 814 espèces. Cela fait des Caudovirales l'ordre le plus peuplé parmi les virus, représentant environ 30% de toutes les espèces de virus reconnues et près de la moitié de tous les genres de virus.[3]

Infection

En rencontrant une bactérie hôte, la queue du virion s'attache aux récepteurs présents à la surface cellulaire et délivre l'ADN dans la bactérie. La queue du virus perce un trou dans la paroi cellulaire bactérienne et la membrane plasmique, le génome passe par la queue et rentre dans la bactérie. Une fois à l'intérieur, les gènes sont exprimés à partir de la machinerie génomique de l'hôte, en utilisant les ribosomes de ce dernier[2].

Taxonomie

Un total de 14 familles ainsi qu'un genre incertae sedis ont été attribués à l'ordre[3] :

Voir également

  • Xu J, Hendrix RW, Duda RL, « Conserved translational frameshift in dsDNA bacteriophage tail assembly genes », Molecular Cell, vol. 16, no 1,‎ octobre 2004, p. 11–21 (PMID , DOI )
  • Casjens SR, « Comparative genomics and evolution of the tailed-bacteriophages », Current Opinion in Microbiology, vol. 8, no 4,‎ août 2005, p. 451–8 (PMID , DOI )

Références

  • (en) Cet article est partiellement ou en totalité issu de l’article de Wikipédia en anglais intitulé .
  1. Tailed bacteriophages: the order caudovirales, vol. 51, 1998, 135–201 p. (ISBN 9780120398515, PMID , DOI )
  2. a b c et d « Double-Stranded DNA Bacteriophages » , Boundless, 11 novembre 2017
  3. a et b « Virus Taxonomy: 2020 Release », International Committee on Taxonomy of Viruses (ICTV), mars 2021 (consulté le 11 mai 2021)
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wikipedia FR

Caudovirales: Brief Summary

provided by wikipedia FR
 src= Structure du bactériophage à queue : (1) tête, (2) queue, (3) ADN, (4) capside, (5) collier, (6) gaine, (7) fibres constituant la queue, (8) spicules  src= Micrographie électronique à transmission (MET) de Gamma-Phage

Caudovirales est un ordre de virus connus sous le nom de bactériophages à queue (cauda signifie en latin « queue »). Selon la classification de Baltimore , Caudovirales est un ordre de virus du groupe I, leur génomes étant à ADN double brin (ADNds), qui peuvent avoir une longueur comprise entre 18 000 paires de bases et 500 000 paires de bases. Les virions ont une forme distincte, chacun possédant une tête icosaédrique qui contient le génome viral et qui est attaché à une queue flexible à l'aide d'une protéine connectrice. L'ordre englobe un large éventail de virus, dont la plupart contiennent des gènes de séquences nucléotidiques et de fonctions similaires. Cependant, certains génomes de bactériophages à queue peuvent varier de manière assez significative dans la séquence nucléotidique, et ce même au sein du même genre. En raison de leur structure caractéristique et de la possession de gènes potentiellement homologues, on pense que ces bactériophages possèdent une origine commune.

Cette ordre contient 14 familles, 73 sous-familles, 927 genres et 2 814 espèces. Cela fait des Caudovirales l'ordre le plus peuplé parmi les virus, représentant environ 30% de toutes les espèces de virus reconnues et près de la moitié de tous les genres de virus.

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fr
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wikipedia FR