18 nm, provided with a base plate and 6 short fibers.
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Type Species |
(Mu) |
The viral genome contains two terminal, variable sequences of host DNA and is able to integrate at any site of the host chromosome and to generate a wide range of mutations due to its unique mode of DNA replication (transposition). Integration is required for both lytic and lysogenic development.
Virions have icosahedral heads of about 60 nm in diameter and tails of about 120 18 nm, provided with a base plate and 6 short fibers.
Physicochemical and Physical Properties
Virion buoyant density in CsC1 is 1.49 g/cm3.
Genomes are about 39 kbp in size, corresponding to about 40% of particle weight, and have a G+C content of 50-51%.
Particles have 12 structural proteins (Mr 20-76 103), including two major CPs (Mr 36 and 48 103).
Not known.
Not known.
Genome Organization and Replication
The genetic map is linear and includes at least 50 genes. Related functions cluster together. The genome is nonpermuted and heterogeneous, consisting of about 37 kbp of phage-specific DNA flanked at both ends by 0.5-3 kbp covalently bound segments of host DNA. It contains an invertible segment of 3 kbp (G-loop) that is homologous to the C-segment of Enterobacteria phage P1 (P1) DNA. Infecting DNA forms circles by means of a terminal protein and undergoes lytic or lysogenic development. Both modes require (random) integration of phage DNA, mediated by a transposase. Transcription starts at the left end of the genome and depends on host RNA polymerase. Replication may start at either end of the genome, is semi-conservative, and occurs during transposition into new integration sites. Phage heads package nonconcatemeric phage DNA and adjacent host DNA by a headful mechanism. Progeny phage DNA is cut within the host DNA 100 to 200 bp away from a phage-coded pac site.
Enterobacteriophages Mu, D108, P1, and P2 have common tail fiber antigens.
Viruses are temperate and general transductants, and infect enterics and (possibly) related Gram-negative bacteria. The invertible G-loop codes for two sets of tail fibers and provides a means of extending host range. Prophages are non-inducible by UV light.
Phages Mu, D108, and P1 share a 3 kbp-size segment that codes for tail fibers.
List of Species Demarcation Criteria in the Genus
Not applicable.
Official virus species names are in italics. Tentative species names, alternative names ( ), strains or serotypes are not italicized. Virus names and assigned abbreviations ( ) are:
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Enterobacteria phage Mu |
(Mu) |
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(Enterobacteria phage ) |
() |
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(Enterobacteria phage Mu-1) |
(Mu-1) |
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Enterobacteria phage D108 |
(D108) |
Tentative Species in the Genus
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Vibrio phage VcA3 |
(VcA3) |
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