Siphoviridae are a family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of double-stranded DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 virus

Virus

A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

es infecting only bacteria. The characteristic features of this family is the presence of a head and non contractile tail.

There are at least 256 species in this family.

Virology

The virons are nonenveloped and have a long filamentous non-contractile tail and an isometric capsid

Capsid

A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...

 (morphotype B1) or a prolate capsid (morphotype B2). The icosahedral capsid (T = 7) is ~55-60 nm in diameter. It is composed of 72 capsomers that appear hexagonal in outline.

The filamentous cross banded tail can reach to 570 nm. It has a width of and a width of ~8 nm and is non contractile. It has short terminal and subterminal fibers.

The genome

Genome

In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....

 is double stranded and linear. It is typically ~50 kilobases in length and contains ~70 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

s. The guanine

Guanine

Guanine is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine . In DNA, guanine is paired with cytosine. With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with...

 + cytosine

Cytosine

Cytosine is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine . It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached . The nucleoside of cytosine is cytidine...

 content is ~52%.

Taxonomy

The majority (220 of 256 as of November 2010) of viruses which have been characterized as Siphoviridae based on their morphology do not fall into any of the formentioned genera and are currently classified as 'unclassified Siphoviridae'.http://img.jgi.doe.gov/cgi-bin/pub/main.cgi?section=TreeFile&page=domain&domain=viruses&domainfile=treeviruses17734_9087b5f6e60d62d71f3beb7745a2ee82&openfile=treestate17749_9087b5f6e60d62d71f3beb7745a2ee82&selectedfile=treestate17734_9087b5f6e60d62d71f3beb7745a2ee82&close=e14-#e14-

The organisation of genes in L5-, lambda-, phiC31-, psiM2-, Sfi21-, Sfi11-, sk1- and TM4-like genera suggests that these may form a lamba supergroup (or subfamily).

The c2 like viruses have oblate heads.

The following viruses have been classified into genera:

• Genus c2-like viruses; type species: Lactococcus phage c2
  • Species:
    • Lactococcus phage bIL67
    • Lactococcus phage c2

• Genus L5-like viruses; type species: Mycobacterium phage L5
  • Species:
    • Mycobacteria phage D29
    • Mycobacterium phage L5

• Genus Lambda-like viruses; type species: Enterobacteria phage lambda
  • Species:
    • Enterobacteria phage HK022
    • Enterobacteria phage HK97
    • Enterobacteria phage lambda

• Genus N15-like viruses; type species: Enterobacteria phage N15
  • Species
    • Enterobacteria phage N15

• Genus PhiC31-like viruses; type species: Streptomyces phage phiC31
  • Species
    • Streptomyces phage phiC31

• Genus PsiM1-like viruses; type species: Methanobacterium phage psiM1
  • Species
    • Methanobacterium phage psiM1

• Genus sk1-like viruses
  • Species

• Genus Sfi11-like viruses
  • Species

• Genus r1t-like viruses
  • Species
    • Lactococcus phage r1t

• Genus Sfi21-like viruses
  • Species
    • Lactobacillus casei phage A2
    • Streptococcus thermophilus phage 7201

• Genus SPbeta-like viruses; type species: Bacillus phage SPbeta
  • Species
    • Bacillus phage SPbeta

• Genus T1-like viruses; type species: Enterobacteria phage T1
  • Species
    • Enterobacteria phage T1

• Genus T5-like viruses; type species: Enterobacteria phage T5
  • Species:
    • Enterobacteria phage T5
    • Vibrio phage 149 (type IV)

Unclassified

• Species
  • phage HF1
  • phage HF2
  • mycobacteriophage TM4
  • mycobacteriophage Adephagia
  • mycobacteriophage Anaya
  • mycobacteriophage Angelica
  • mycobacteriophage CrimD
  • mycobacteriophage Pixie
  • Staphylococcus aureus phage SAP-26

External links

• Viralzone: Siphoviridae