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Type Species |
(T4) |
Virions are large, have elongated heads, and produce morphological aberrations. Tails have long, kinked fibers. Genomes are circularly permuted and terminally redundant, and typically code for hydroxymethylcytosine (HMC) and type B DNA polymerase. The genetic map is circular and the DNA is packaged by a headful mechanism.
Phage heads are prolate icosahedra (elongated pentagonal bipyramidal antiprisms), measure about 111 78 nm, and consist of 152 capsomers (T = 13). Tails measure 113 16 nm and have a collar, base plate, 6 short spikes and 6 long fibers.
Physicochemical and Physical Properties
Virion Mr is 210 106, buoyant density in CsCl is 1.51 g/cm3; S20w is about 1030S. Infectivity is ether and chloroform resistant.
Genomes have a Mr of about 120 106 (169 kbp), corresponding to 48% of particle weight, inasmuch as known contain 5-hydroxymethylcytosine (HMC) instead of thymine and are glycosylated, have a G+C content of 35%, and are circularly permuted and terminally redundant. The Enterobacteria phage T4 (T4) genome has been fully sequenced (168,726 bp).
Particles contain at least 42 polypeptides (Mr 8-155 103), including 1,600-2,000 copies of the major capsid protein (Mr 43 103); 3 proteins are located inside the head. Various enzymes are present or coded for, e.g., type B (E. coli Pol II) DNA polymerase, dihydrofolate reductase and lysozyme. ATP is associated with the tail. Amino acid sequences for T4 are available at GenBank and EMBL. See Fig. 1.
Not known.
Glucose is covalently linked to HMC in phage DNA. Gentiobiose may be present.
Genome Organization and Replication
The genetic map is circular and comprises about 200 genes (Fig. 2). Morphopoietic genes generally cluster together, but the whole genome appears disorganized, suggesting extensive translocation of genes during evolution. The genome is circularly permuted and has a terminal redundancy of 1-3%. After infection, the host chromosome breaks down and viral DNA replicates as a concatemer, generating forked replicative intermediates from multiple origins of replication. Transcription is regulated in part by phage-induced modification of host bacterial RNA polymerase and proceeds in three waves (early, middle, late). Heads, tails, and tail fibers are assembled in 3 separate pathways. Unique DNA molecules are packaged by a headful mechanism without pac sites. Virions are assembled at the cell periphery. Aberrant head structures (polyheads, isometric heads) are frequent.
A group antigen and antigens defining 8 subgroups have been identified by complement fixation.
Phages are virulent, and infect enterics and related bacteria (3-subgroup of purple Gram-negative bacteria). Their distribution is worldwide.
List of Species Demarcation Criteria in the Genus
Species differ in host range, capsid length, serological properties and, insofar as known, DNA homology and amino acid sequences of major capsid protein (CP) gp23. Capsid length is 137 nm for Aeromonas phage Aeh1 (Aeh1) and Vibrio phage nt-1 (nt-1) and 111 nm in the other species. Species T4 and Enterobacteria phage SV14 (SV14) are DNA hybridization groups.
Official virus species names are in italics. Tentative species names, alternative names ( ), strains or serotypes are not italicized. Virus names, genome sequence accession numbers [ ], and assigned abbreviations ( ) are:
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Acinetobacter phage 133 |
(133) | |
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Aeromonas phage 40RR2.8t |
(40RR2.8t) | |
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Aeromonas phage 40R |
(40R) | |
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Aeromonas phage Aeh1 |
(Aeh1) | |
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Aeromonas phage 65 |
(65) | |
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Enterobacteria phage SV14 |
(SV14) | |
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Enterobacteria phage D2A |
(D2A) | |
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Enterobacteria phage D8 |
(D8) | |
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Enterobacteria phage T4 |
[seq_phgT4] |
(T4) |
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Enterobacteria phage C16 |
(C16) | |
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Enterobacteria phage F10 |
(F10) | |
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Enterobacteria phage Fs |
(Fs) | |
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Enterobacteria phage PST |
(PST) | |
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Enterobacteria phage SKII |
(SKII) | |
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Enterobacteria phage SKV |
(SKV) | |
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Enterobacteria phage SKX |
(SKX) | |
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Enterobacteria phage SV3 |
(SV3) | |
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Enterobacteria phage T2 |
(T2) | |
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Enterobacteria phage T6 |
(T6) | |
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Pseudomonas phage 42 |
(42) | |
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Vibrio phage nt-1 |
(nt-1) | |
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Vibrio phage KVP20 |
(KVP20) | |
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Vibrio phage KVP40 |
(KVP40) |
Tentative Species in the Genus
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Acinetobacter phage E4 |
(E4) |
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Acinetobacter phage E5 |
(E5) |
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Aeromonas phage 1 |
(1) |
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Aeromonas phage 25 |
(25) |
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Aeromonas phage 31 |
(31) |
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Enterobacteria phage 1 (syn. P. aeI) |
(1) |
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Enterobacteria phage 11F |
(11F) |
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Enterobacteria phage 3 |
(3) |
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Enterobacteria phage 3T+ |
(3T+) |
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Enterobacteria phage 50 |
(50) |
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Enterobacteria phage 5845 |
(5845) |
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Enterobacteria phage 66F |
(66F) |
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Enterobacteria phage 8893 |
(8893) |
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Enterobacteria phage 9/0 |
(9/0) |
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Enterobacteria phage 1 |
(1) |
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Enterobacteria phage DdVI |
(DdVI) |
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Enterobacteria phage F7 |
(F7) |
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Enterobacteria phage Kl3 |
(Kl3) |
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Enterobacteria phage RB42 |
(RB42) |
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Enterobacteria phage RB43 |
(RB43) |
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Enterobacteria phage RB49 |
(RB49) |
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Enterobacteria phage RB69 |
(RB69) |
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Enterobacteria phage SMB |
(SMB) |
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Enterobacteria phage SMP2 |
(SMP2) |
The genus includes about 100 isolates of uncertain taxonomic status; these are either strains of the Enterobacteria phage T4 species or represent independent species.
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