Enterobacteria phage T4

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Enterobacteria phage T4
Tevenphage.svg
Virus classification
Group: Group I (dsDNA)
Order: Caudovirales
Family: Myoviridae
Genus: T4-like viruses
Species: Enterobacteria phage T4

Enterobacteria phage T4 is a bacteriophage that infects Escherichia coli bacteria. The T4 phage is a member of the T-even phages, a group including enterobacteriophages T2 and T6. T4 is capable of undergoing only a lytic lifecycle and not the lysogenic lifecycle.

Genome and structure[edit]

The T4 phage's double-stranded DNA genome is about 169 kbp long[1] and encodes 289 proteins. The T4 genome is terminally redundant and is first replicated as a unit, then several genomic units are recombined end-to-end to form a concatemer. When packaged, the concatemer is cut at unspecific positions of the same length, leading to several genomes that represent circular permutations of the original.[2] The T4 genome bears eukaryote-like intron sequences.

Translation[edit]

The Shine-Dalgarno sequence GAGG dominates in bacteriophage T4 early genes, whereas the sequence GGAG is a target for the T4 endonuclease RegB that initiates the early mRNA degradation.[3]

Virus particle structure[edit]

T4 is a relatively large phage, at approximately 90 nm wide and 200 nm long (most phages range from 25 to 200 nm in length). The DNA genome is held in an icosahedral head, also known as a capsid. The T4’s tail is hollow so that it can pass its nucleic acid into the cell it is infecting after attachment. The tail attaches to a host cell with the help of tail fibres. The tail fibres are also important in recognizing host cell surface receptors, so they determine if a bacterium is within the phage's host range.[citation needed]

Infection process[edit]

The T4 phage initiates an E. coli infection by binding OmpC porin proteins and Lipopolysaccharide (LPS) on the surface of E. coli cells with its long tail fibers (LTF).[4][5] A recognition signal is sent through the LTFs to the baseplate. This unravels the short tail fibers (STF) that bind irreversibly to the E. coli cell surface. The baseplate changes conformation and the tail sheath contracts, causing GP5 at the end of the tail tube to puncture the outer membrane of the cell. The lysozyme domain of GP5 is activated and degrades the periplasmic peptidoglycan layer. The remaining part of the membrane is degraded and then DNA from the head of the phage can travel through the tail tube and enter the E. coli cell.

Life cycle[edit]

The lytic lifecycle (from entering a bacterium to its destruction) takes approximately 30 minutes (at 37 °C) and consists of:[citation needed]

After the life cycle is complete, the host cell bursts open and ejects the newly built viruses into the environment, destroying the host cell. T4 has a burst size of approximately 100-150 viral particles per infected host. Complementation, deletion, and recombination tests can be used to map out the rII gene locus by using T4. These bacteriophage infect a host cell with their information and then blow up the host cell, thereby propagating themselves.

Replication and packaging[edit]

It has a fast and highly accurate DNA copying mechanism, with only 1 error in 300 copies. The phage also codes for unique DNA repair mechanisms. The T4 DNA packaging motor has been found to load DNA into phage capsids at a rate up to 2000 base pairs per second. The power involved, if scaled up in size, would be equivalent to that of an average automobile engine.[6]

History[edit]

The specific time and place of T4 phage isolation remains unclear, though they were likely found in sewage or fecal material. T4 and similar phages were described in a paper by Thomas F. Anderson, Max Delbrück, and Milislav Demerec in November 1944.[7]

A number of Nobel Prize winners worked with phage T4 or T4-like phages including Max Delbrück, Salvador Luria, Alfred Hershey, James D. Watson, and Francis Crick. Other important scientists who worked with phage T4 include Michael Rossmann, Seymour Benzer, Bruce Alberts, Gisela Mosig,[8] Richard Lenski, and James Bull.

See also[edit]

References[edit]

  1. ^ Miller, ES; Kutter, E; Mosig, G; Arisaka, F; Kunisawa, T; Rüger, W (March 2003). "Bacteriophage T4 genome.". Microbiology and molecular biology reviews : MMBR 67 (1): 86–156, table of contents. doi:10.1128/MMBR.67.1.86-156.2003. PMC 150520. PMID 12626685. 
  2. ^ Madigan M, Martinko J (editors) (2006). Brock Biology of Microorganisms (11th ed.). Prentice Hall. ISBN 0-13-144329-1. 
  3. ^ Malys N (2012). "Shine-Dalgarno sequence of bacteriophage T4: GAGG prevails in early genes". Molecular Biology Reports 39 (1): 33–9. doi:10.1007/s11033-011-0707-4. PMID 21533668. 
  4. ^ Yu, F.; Mizushima, S. (1982). "Roles of lipopolysaccharide and outer membrane protein OmpC of Escherichia coli K-12 in the receptor function for bacteriophage T4". Journal of bacteriology 151 (2): 718–722. PMC 220313. PMID 7047495.  edit
  5. ^ Furukawa, H.; Mizushima, S. (1982). "Roles of cell surface components of Escherichia coli K-12 in bacteriophage T4 infection: Interaction of tail core with phospholipids". Journal of bacteriology 150 (2): 916–924. PMC 216445. PMID 7040345.  edit
  6. ^ Rao, Venigalla B; Black, Lindsay W (1 January 2010). "Structure and assembly of bacteriophage T4 head". Virology Journal 7 (1): 356. doi:10.1186/1743-422X-7-356. 
  7. ^ Abedon, ST (June 2000). "The murky origin of Snow White and her T-even dwarfs.". Genetics 155 (2): 481–6. PMC 1461100. PMID 10835374. 
  8. ^ Nossal, NG; Franklin, JL; Kutter, E; Drake, JW (November 2004). "Anecdotal, historical and critical commentaries on genetics. Gisela Mosig.". Genetics 168 (3): 1097–104. PMID 15579671. 

Further reading[edit]

External links[edit]