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T7 Bacteriophage - Enterobacteria phage T7

Classification

Viruses; Duplodnaviria; Heunggongvirae; Uroviricota; Caudoviricetes; Autographiviridae; Studiervirinae; Teseptimavirus

Species

Teseptimavirus T7

Description and Significance

Like other viruses, the T7 bacteriophage does not produce its own energy. Instead, it infiltrates a bacterium via a membrane protein, and alters the genome in the nuclear envelope. By doing this, the T7 bacteriophage interferes with the protein synthesis and metabolic pathways of the bacteria into producing viral proteins and packaging them with the viruses genome.

Genome Structure

The genome of the T7 Bacteriophage is comprised of approximately 40,000 bp of DNA coding for 55 proteins. Many of these genes are overlapping and are removed via refactoring of the genome.

Structure and Life Cycle

The T7 Bacteriophage possesses an icosahedral capsid shell made by gene product 10, and a 12-fold portal, a feature commonly found in tailed bacteriophages and herpesviruses. (Chen, Xiao, Wang, Cheng 2021) The T7 bacteriophage has a tail with a 12-fold adaptor protein gp11 assembly, a sixfold nozzle protein gp12 assembly, and six subunits of trimeric tail fiber gp17. The tail fibers of the T7 bacteriophage are used to recognize potential hosts, and absorb into them. On top of the portal, the hollow capsid shell can be found.

The life cycle of a T7 bacteriophage consists of three primary steps. Firstly, the phage searches for and absorbs into a host; in the second step, the phage transfers its linear DNA genome into a host cell and expresses its phage genes. Third, the host cell is lysed and releases the newly assembled phages. (Nguyen, Kang 2014) On the surface, the T7 bacteriophage targets a lipopolysaccharide receptor, which binds to the C-terminal end of the T7 tail fiber protein. (Nguyen, Kang 2014) The DNA of the phage is translocated into the host in a process dependent on transcription, which is performed by the hosts RNA polymerase and then by the T7 phages RNA polymerase.

References

U.S. National Library of Medicine. (n.d.). Taxonomy browser (escherichia phage T7). National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=10760&lvl=3&lin=f&keep=1&srchmode=1&unlock

Nguyen, H. M., & Kang, C. (2014, February). Lysis delay and burst shrinkage of coliphage T7 by deletion of Terminator Tφ reversed by deletion of early genes. Journal of virology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3911561/#:~:text=The%20replication%20cycle%20of%20phage,release%20newly%20assembled%20phage%20progenies.

Chen, W., Xiao, H., Wang, L., & Cheng, L. (2021, September 9). Structural changes in bacteriophage T7 upon receptor-induced ... - PNAS. PNAS. https://www.pnas.org/doi/full/10.1073/pnas.2102003118