Genus “T1-like Viruses”

Type Species	Enterobacteria phage T1	(T1)

Distinguishing Features

Tails are extremely flexible. Phage DNA has pac sites and is terminally redundant and circularly permuted.

Virion Properties

Morphology

Virions have icosahedral heads of about 60  nm and extremely flexible tails of 151 8  nm provided with 4 short, kinked, terminal fibers. The flexible nature of the tail is best seen after phosphotungstate staining.

Physicochemical and Physical Properties

Virion buoyant density in CsC1 is 1.5  g/cm³.

Nucleic Acid

Genomes are about 49  kbp in size and have a G+C content of about 48%.

Proteins

Virions contain at least 14 proteins including two major head proteins (Mr 26 and 33 10³).

Lipids

Not known.

Carbohydrates

Not known.

Genome Organization and Replication

The genetic map is linear and comprises 36-41 genes; related functions cluster together (Fig. 2). The genome is circularly permuted and terminally redundant (2.8  kbp or 6% of genome), and includes a recombinational hot spot. Host syntheses are inhibited after infection. The mechanism of Enterobacteria phage T1 replication is little known. Progeny DNA is cut from concatemers at pac sites and packaged by a headful mechanism.

Biological Properties

Phages are virulent and general transductants, and infect enterobacteria.

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 and assigned abbreviations ( ) are:

Species in the Genus

Enterobacteria phage T1	(T1)

Tentative Species in the Genus

Enterobacteria phage 102	(102)
Enterobacteria phage 103	(103)
Enterobacteria phage 150	(150)
Enterobacteria phage 168	(168)
Enterobacteria phage 174	(174)
Enterobacteria phage 4	(4)
Enterobacteria phage D20	(D20)
Enterobacteria phage	()
Enterobacteria phage Hi	(Hi)
Enterobacteria phage UC-1	(UC-1)

About 50 more enterobacterial phages are considered as relatives of Enterobacteria phage T1 on morphological grounds.