spbetavirus spbetavirus spbetavirus (formerly spbetalikevirus and sometimes spbeta-like viruses) is a genus of viruses in the order caudovirales, in the family siphoviridae. bacteria serve as natural hosts. there is only one species in this genus: bacillus virus spbeta. spbetavirus virus classification (unranked): virus realm: duplodnaviria kingdom: heunggongvirae phylum: uroviricota class: caudoviricetes order: caudovirales family: siphoviridae genus: spbetavirus synonyms spbetalikevirus bacillus phage spbeta structure spbetaviruses are nonenveloped, with a head and tail. the head is about 81 nm in diameter. the tail is long, but fairly rigid, at about 355 nm long, 10 nm wide. it has six club-shaped terminal fibers and no collar. genusstructuresymmetrycapsidgenomic arrangementgenomic segmentation spbetavirushead-tailt=7non-envelopedlinearmonopartite genome genomes are linear, around 134kb in length. bacillus phage spbeta has been fully sequenced. it has about 134k nucleotides, with 185 proteins. the complete genome is available here life cycle viral replication is cytoplasmic. the virus attaches to the host cell's adhesion receptors using its terminal fiber, and degrades the cell wall using viral exolysin enough to eject the viral dna into the host cytoplasm via long flexible tail ejection system. replication follows the replicative transposition model. dna-templated transcription is the method of transcription. 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. bacteria serve as the natural host. transmission routes are passive diffusion. genushost detailstissue tropismentry detailsrelease detailsreplication siteassembly sitetransmission spbetavirusbacterianoneinjectionlysiscytoplasmcytoplasmpassive diffusion history according to ictv's ninth report, the genus spbetalikevirus was first accepted under the name spbeta-like viruses, assigned to family siphoviridae, order caudovirales. the genus was renamed to spbetalikevirus in 2012. the genus was renamed spbetalikevirus in 2015.