Genus “-like Viruses”

Type Species	Enterobacteria phage	()

Distinguishing Features

The DNA has cohesive ends and is packaged as a unit-size filament.

Virion Properties

Morphology

Phage heads are icosahedra, measure about 60  nm in diameter, and consist of 72 capsomers (60 hexamers, 12 pentamers, T = 7). Tails are flexible, measure 150 8  nm, and have short terminal and subterminal fibers (Fig. 1).

Physicochemical and Physical Properties

Virion Mr is about 60 10⁶; buoyant density in CsCl is 1.50  g/cm³; S_20w is about 390S. Infectivity is ether-resistant.

Nucleic Acid

Genomes are about 48,502  bp in size, corresponding to 54% of particle weight, have G+C contents of 52% and cohesive ends, and are nonpermuted. The genome has been fully sequenced.

Proteins

Virions contain 9 structural proteins (Mr 17-130 10³), including 420 copies each of major capsid proteins D and E (Mr 38 and 53 10³). Amino acid sequences are available at GenBank and EMBL.

Lipids

None reported.

Carbohydrates

None reported.

Genome Organization and Replication

The genome includes about 50 genes and has cohesive ends. Related functions cluster together. The infecting DNA circularizes and replicates or integrates into the host genome. Transcription starts in the immunity region and proceeds in three waves. Bidirectional DNA replication as a structure, starting from a single site, is followed by unidirectional replication via a rolling-circle mechanism. There is no breakdown of host DNA. Proheads are frequent in lysates.

Biological Properties

Phages are temperate and apparently specific for enterobacteria. Prophages generally integrate at specific sites and are UV-inducible.

List of Species Demarcation Criteria in the Genus

Not applicable.

List of Species in the Genus

Official virus species names are in italics. Tentative virus species names, alternative names ( ), strains or serotypes are not italicized. Virus names, genome sequence accession numbers [ ], and assigned abbreviations ( ) are:

Species in the Genus

Enterobacteria phage	[J02459]	()

Tentative Species in the Genus

Enterobacteria phage HK022	(HK022)
Enterobacteria phage HK97	(HK97)
Enterobacteria phage PA-2	(PA-2)
Enterobacteria phage D328	(D328)
Enterobacteria phage 80	(80)
Rhizobium phage 16-6-2	(16-6-2)