| Lambdavirus | |
|---|---|
Virus classification  | |
| (unranked): | Virus |
| Realm: | Duplodnaviria |
| Kingdom: | Heunggongvirae |
| Phylum: | Uroviricota |
| Class: | Caudoviricetes |
| Genus: | Lambdavirus |
Lambdavirus is a genus of viruses in the class Caudoviricetes . Bacteria serve as natural hosts, with transmission achieved through passive diffusion. There are five species in this genus. [1] [2] [3]
The following species are recognized: [2]
The genus also includes several unclassified viruses—including the corynephages β and ω, which infect Corynebacterium diphtheriae and carry the deadly diphtheria toxin. [4] [5]
Lambdaviruses are nonenveloped, with a head and tail. The head is about 60 nm in diameter, consisting of 72 capsomers (T=7, levo). [1]
| Genus | Structure | Symmetry | Capsid | Genomic arrangement | Genomic segmentation |
|---|---|---|---|---|---|
| Lambdavirus | Head-Tail | T=7, levo | Non-enveloped | Linear | Monopartite |
All species have been fully sequenced. They range between 42k and 49k nucleotides, with 56 to 73 proteins. [3]
The virus attaches to the host cell's adhesion receptors using its terminal fiber, and ejects the viral DNA into the host cytoplasm via long flexible tail ejection system. Viral replication is cytoplasmic. Replication follows the replicative transposition model. DNA-templated transcription is the method of transcription. Translation takes place by -1 ribosomal frameshifting, and +1 ribosomal frameshifting. Once the viral genes have been replicated, the procapsid is assembled and packed. The tail is then assembled and the mature virions are released via lysis, and holin/endolysin/spanin proteins. Bacteria serve as the natural host. Transmission routes are passive diffusion. [1]
| Genus | Host details | Tissue tropism | Entry details | Release details | Replication site | Assembly site | Transmission |
|---|---|---|---|---|---|---|---|
| Lambdavirus | Bacteria | None | Injection | Lysis | Cytoplasm | Cytoplasm | Passive diffusion |
According to ICTV's taxon history: [6]
The scope of the genus has changed significantly in its evolution. Originally a group of all so-called lambdoid phages (synonyms Lambda-like viruses, Lambda-like phages, Lambda phage group), its scope has narrowed significantly.
Given the above history, the latest document that defines the boundary of the genus is the 2017 document that created Hk97virus. Unfortunately the document does not specifically address the inclusion criteria for Lambdavirus, only the evidence for their new genus being monophyletic and reasonably similar with each other. The only part that shows the similarity among the members of Lambdavirus was in figure 2, a Gegenees BLASTN analysis using window of 100 bp and a slide of 50 bp. The lowest Gegeenes similarity among members of the group was 62.5%. [10] The general guideline from ICTV's Bacterial and Archaeal Viruses Subcommitee in 2017 was 50% nucleotide similarity. [11]
The term lambdoid phage remains commonly used. It originally consisted of an operational definition of "phages that can recombine with lambda and form a functional, recombinant phage". The term was slightly expanded in the genomic era to mean phages that have a similar-enough functional gene order and at least some patch of homology so that, if hypothetically recombined with lambda, it would form a functional phage with all required genes. [12] The possibility of recombination does not necessarily imply a recent common ancestor and the apparently recombinant character of P22 adds to the problem. [13] Phages that have been called lambdoid include members as diverse as Lederbergvirus P22 , Byrnievirus HK97 , Salmonella phage ES18, Salmonella phage Gifsy-2, and Traversvirus tv933W . [14]