Escherichia virus T4
Escherichia virus T4 | |
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Escherichia virus T4 ( virion )
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Virus classification | |
(unranked): | Virus |
Realm: | Duplodnaviria |
Kingdom: | Heunggongvirae
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Phylum: | Uroviricota |
Class: | Caudoviricetes |
Order: | Caudovirales |
Family: | Myoviridae |
Genus: | Tequatrovirus |
Species: | Escherichia virus T4
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Strains[2] | |
Synonyms[3] | |
Enterobacteria phage T4 |
Escherichia virus T4 is a species of
Use in research
Dating back to the 1940s and continuing today, T-even phages are considered the best studied model organisms.
Genome and structure
The T4 virus's double-stranded
sequences.Translation
The
Virus particle structure
T4 is a relatively large virus, at approximately 90
The structure of the 6 megadalton T4 baseplate that comprises 127 polypeptide chains of 13 different proteins (gene products 5, 5.4, 6, 7, 8, 9, 10, 11, 12, 25, 27, 48 and 53) has recently been described in atomic detail. An atomic model of the proximal region of the tail tube formed by gp54 and the main tube protein gp19 have also been created. The tape measure protein gp29 is present in the baseplate-tail tube complexes, but it could not be modeled.[12]
During assembly of the bacteriophage (phage) T4 virion, the morphogenetic proteins encoded by the phage genes interact with each other in a characteristic sequence. Maintaining an appropriate balance in the amounts of each of these proteins produced during viral infection appears to be critical for normal phage T4 morphogenesis.[13] Phage T4 encoded proteins that determine virion structure include major structural components, minor structural components and non-structural proteins that catalyze specific steps in the morphogenesis sequence.[14] Phage T4 morphogenesis is divided into three independent pathways: the head, the tail and the long tail fibres as detailed by Yap and Rossman.[15]
Infection process
The T4 virus initiates an Escherichia coli infection by binding OmpC porin proteins and lipopolysaccharide (LPS) on the surface of E. coli cells with its long tail fibers (LTF).[16][17] 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.[18] 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 virus can travel through the tail tube and enter the E. coli cell.[citation needed]
In 1952, Hershey and Chase[19] provided key evidence that the phage DNA, as distinct from protein, enters the host bacterial cell upon infection and is thus the genetic material of the phage. This finding suggested that DNA is, in general, the genetic material of different organisms.[citation needed]
Reproduction
The lytic life cycle (from entering a bacterium to its destruction) takes approximately 30 minutes (at 37 °C). Virulent bacteriophages multiply in their bacterial host immediately after entry. After the number of progeny phages reach a certain amount, they cause the host to lyse or break down, therefore they would be released and infect new host cells.[20] The process of host lyses and release is called the lytic cycle. Lytic cycle is a cycle of viral reproduction that involves the destruction of the infected cell and its membrane. This cycle involves a virus that overtakes the host cell and its machinery to reproduce. Therefore, the virus must go through 5 stages in order to reproduce and infect the host cell:[citation needed]
- Adsorption and penetration (starting immediately)
- Arrest of host gene expression (starting immediately)
- Enzyme synthesis (starting after 5 minutes)
- DNA replication (starting after 10 minutes)
- Formation of new virus particles (starting after 12 minutes)
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.[citation needed]
Benzer (1955 – 1959) developed a system for studying the fine structure of the gene using bacteriophage T4 mutants defective in the rIIA and rIIB genes.[21][22][23] The techniques employed were complementation tests and crosses to detect recombination, particularly between deletion mutations. These genetic experiments led to the finding of a unique linear order of mutational sites within the genes. This result provided strong evidence for the key idea that the gene has a linear structure equivalent to a length of DNA with many sites that can independently mutate.[citation needed]
Adsorption and penetration
Just like all other viruses, T-even phages do not randomly attach to the surface of their host; instead they "search" and bind to
Penetration is also a value characteristic of phage-host
Replication and packaging
Virus T4 genome is synthesized within the host cell using rolling circle replication.[6] The time it takes for DNA replication in a living cell was measured as the rate of virus T4 DNA elongation in virus-infected E. coli.[26] During the period of exponential DNA increase at 37 °C, the rate was 749 nucleotides per second. The mutation rate per base pair per replication during virus T4 DNA synthesis is 1.7 per 10−8,[27] a highly accurate DNA copying mechanism, with only 1 error in 300 copies. The virus also codes for unique DNA repair mechanisms.[28] The T4 phage head is assembled empty around a scaffolding protein, which is later degraded. Consequently, the DNA needs to enter the prohead through a tiny pore, which is achieved by a hexamer of gp17 interacting with DNA first, which also serves as a motor and nuclease. The T4 DNA packaging motor has been found to load DNA into virus 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.[29]
Release
The final step in viral reproduction and multiplication is determined by the release of virions from the host cell. The release of the virions occurs after the breakage of the bacterial plasma membrane. Nonenveloped viruses lyse the host cell which is characterized by viral proteins attacking the peptidoglycan or membrane. The lysis of the bacteria occurs when the capsids inside the cell release the enzyme lysozyme which break down the cell wall. The released bacteriophages infect other cells, and the viral multiplication cycle is repeated within those cells.[citation needed]
Multiplicity reactivation
Multiplicity reactivation (MR) is the process by which two or more virus genomes, each containing inactivating genome damage, can interact within an infected cell to form a viable virus genome. Salvador Luria, while studying UV irradiated virus T4 in 1946, discovered MR and proposed that the observed reactivation of damaged virus occurs by a recombination mechanism.(see refs.[30][31][32]) This preceded the confirmation of DNA as the genetic material in 1952 in related virus T2 by the Hershey–Chase experiment.[19]
As remembered by Luria (1984,
MR is usually represented by "survival curves" where survival of plaque forming ability of multiply infected cells (multicomplexes) is plotted against dose of genome damaging agent. For comparison, the survival of virus plaque forming ability of singly infected cells (monocomplexes) is also plotted against dose of genome damaging agent. The top figure shows the survival curves for virus T4 multicomplexes and monocomplexes with increasing dose of UV light. Since survival is plotted on a log scale it is clear that survival of multicomplexes exceeds that of monocomplexes by very large factors (depending on dose). The UV inactivation curve for multicomplexes has an initial shoulder. Other virus T4 DNA damaging agents with shoulders in their multicomplex survival curves are X-rays[34][35] and ethyl methane sulfonate (EMS).[28] The presence of a shoulder has been interpreted to mean that two recombinational processes are used.[36] The first one repairs DNA with high efficiency (in the "shoulder"), but is saturated in its ability as damage increases; the second pathway functions at all levels of damage. Surviving T4 virus released from multicomplexes show no increase in mutation, indicating that MR of UV irradiated virus is an accurate process.[36]
The bottom figure shows the survival curves for inactivation of virus T4 by the DNA damaging agent mitomycin C (MMC). In this case the survival curve for multicomplexes has no initial shoulder, suggesting that only the second recombinational repair process described above is active. The efficiency of repair by this process is indicated by the observation that a dose of MMC that allows survival of only 1 in 1,000 monocomplexes allows survival of about 70% of multicomplexes. Similar multicomplex survival curves (without shoulders) were also obtained for the DNA damaging agents P32 decay, psoralen plus near-UV irradiation (PUVA), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), methyl methane sulfonate (MMS) and nitrous acid.[28]
Several of the genes found to be necessary for MR in virus T4 proved to be
History
Bacteriophages were first discovered by the English scientist Frederick Twort in 1915 and Félix d'Hérelle in 1917. In the late 1930s, T. L. Rakieten proposed either a mixture of raw sewerage or a lysate from E. coli infected with raw sewerage to the two researchers Milislav Demerec and Ugo Fano. These two researchers isolated T3, T4, T5, and T6 from E.coli. Also, in 1932, the researcher J. Bronfenbrenner had studied and worked on the T2 phage, at which the T2 phage was isolated from the virus.[39] This isolation was made from a fecal material rather than from sewerage. At any rate, Max Delbrück was involved in the discovery of the T even phages. His part was naming the bacteriophages into Type 1(T1), Type 2 (T2), Type 3 (T3), etc.[citation needed]
The specific time and place of T4 virus isolation remains unclear, though they were likely found in sewage or fecal material. T4 and similar viruses were described in a paper by Thomas F. Anderson, Max Delbrück, and Milislav Demerec in November 1944.[40] In 1943,
The phage group was an informal network of biologists centered on Max Delbrück that carried out basic research mainly on bacteriophage T4 and made numerous seminal contributions to microbial genetics and the origins of molecular biology in the mid-20th century. In 1961, Sydney Brenner, an early member of the phage group, collaborated with Francis Crick, Leslie Barnett and Richard Watts-Tobin at the Cavendish Laboratory in Cambridge to perform genetic experiments that demonstrated the basic nature of the genetic code for proteins.[42] These experiments, carried out with mutants of the rIIB gene of phage T4, showed, that for a gene that encodes a protein, three sequential bases of the gene's DNA specify each successive amino acid of the protein. Thus the genetic code is a triplet code, where each triplet (called a codon) specifies a particular amino acid. They also obtained evidence that the codons do not overlap with each other in the DNA sequence encoding a protein, and that such a sequence is read from a fixed starting point.[citation needed]
During 1962-1964 phage T4 researchers provided an opportunity to study the function of virtually all of the genes that are essential for growth of the phage under laboratory conditions.[43][44] These studies were facilitated by the discovery of two classes of conditional lethal mutants. One class of such mutants is known as amber mutants.[45] Another class of conditional lethal mutants is referred to as temperature-sensitive mutants[46] Studies of these two classes of mutants led to considerable insight into numerous fundamental biologic problems. Thus understanding was gained on the functions and interactions of the proteins employed in the machinery of DNA replication, repair and recombination, and on how viruses are assembled from protein and nucleic acid components (molecular morphogenesis). Furthermore, the role of chain terminating codons was elucidated. One noteworthy study used amber mutants defective in the gene encoding the major head protein of phage T4.[47] This experiment provided strong evidence for the widely held, but prior to 1964 still unproven, "sequence hypothesis" that the amino acid sequence of a protein is specified by the nucleotide sequence of the gene determining the protein. Thus, this study demonstrated the co-linearity of the gene with its encoded protein.
A number of
See also
- T4 rII system
- T2 phage
- T6 phage
- Bacteriophage
- Virology
References
- .
- ^ "ICTV 9th Report (2011) Myoviridae". International Committee on Taxonomy of Viruses (ICTV). Archived from the original on 26 December 2018. Retrieved 26 December 2018.
- ^ "ICTV Taxonomy history: Escherichia virus T4". International Committee on Taxonomy of Viruses (ICTV). Retrieved 26 December 2018.
Caudovirales > Myoviridae > Tevenvirinae > T4virus > Escherichia virus T4
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Further reading
- Leiman P.G., Kanamaru S, Mesyanzhinov V.V., Arisaka F., Rossmann M.G. (2003). "Structure and morphogenesis of bacteriophage T4". Cellular and Molecular Life Sciences. 60 (11): 2356–2370. S2CID 2228357.
- Karam, J., Petrov, V., Nolan, J., Chin, D., Shatley, C., Krisch, H., and Letarov, A. The T4-like phages genome project. https://web.archive.org/web/20070523215704/http://phage.bioc.tulane.edu/. (The T4-like phage full genomic sequence depository)
- Mosig, G., and F. Eiserling. 2006. T4 and related phages: structure and development, R. Calendar and S. T. Abedon (eds.), The Bacteriophages. Oxford University Press, Oxford. (Review of phage T4 biology) ISBN 0-19-514850-9
- Filee J. Tetart F., Suttle C.A., Krisch H.M. (2005). "Marine T4-type bacteriophages, a ubiquitous component of the dark matter of the biosphere". Proc. Natl. Acad. Sci. USA. 102 (35): 12471–6. PMID 16116082. (Indication of prevalence and T4-like phages in the wild)
- Chibani-Chennoufi S., Canchaya C., Bruttin A., Brussow H. (2004). "Comparative genomics of the T4-Like Escherichia coli phage JS98: implications for the evolution of T4 phages". J. Bacteriol. 186 (24): 8276–86. PMID 15576776. (Characterization of a T4-like phage)
- Desplats C, Krisch HM (May 2003). "The diversity and evolution of the T4-type bacteriophages". Res. Microbiol. 154 (4): 259–67. PMID 12798230.
- Miller, E.S., Kutter E., Mosig G., Arisaka F., Kunisawa T., Ruger W. (2003). "Bacteriophage T4 genome". Microbiol. Mol. Biol. Rev. 67 (1): 86–156. PMID 12626685. (Review of phage T4, from the perspective of its genome)
- Desplats C., Dez C., Tetart F., Eleaume H., Krisch H.M. (2002). "Snapshot of the genome of the pseudo-T-even bacteriophage RB49". J. Bacteriol. 184 (10): 2789–2804. PMID 11976309. (Overview of the RB49 genome, a T4-like phage)
- Malys N, Chang DY, Baumann RG, Xie D, Black LW (2002). "A bipartite bacteriophage T4 SOC and HOC randomized peptide display library: detection and analysis of phage T4 terminase (gp17) and late sigma factor (gp55) interaction". J Mol Biol. 319 (2): 289–304. PMID 12051907. (T4 phage application in biotechnology for studying protein interaction)
- Tétart F., Desplats C., Kutateladze M., Monod C., Ackermann H.-W., Krisch H.M. (2001). "Phylogeny of the major head and tail genes of the wide-ranging T4-type bacteriophages". J. Bacteriol. 183 (1): 358–366. PMID 11114936. (Indication of the prevalence of T4-type sequences in the wild)
- Abedon S.T. (2000). "The murky origin of Snow White and her T-even dwarfs". Genetics. 155 (2): 481–6. PMID 10835374. (Historical description of the isolation of the T4-like phages T2, T4, and T6)
- Ackermann HW, Krisch HM (1997). "A catalogue of T4-type bacteriophages". Arch. Virol. 142 (12): 2329–45. S2CID 39369249. Archived from the originalon 1 November 2001. (Nearly complete list of then-known T4-like phages)
- Monod C, Repoila F, Kutateladze M, Tétart F, Krisch HM (March 1997). "The genome of the pseudo T-even bacteriophages, a diverse group that resembles T4". J. Mol. Biol. 267 (2): 237–49. PMID 9096222. (Overview of various T4-like phages from the perspective of their genomes)
- Kutter E., Gachechiladze K., Poglazov A., Marusich E., Shneider M., Aronsson P., Napuli A., Porter D., Mesyanzhinov V. (1995). "Evolution of T4-related phages". Virus Genes. 11 (2–3): 285–297. S2CID 20529415. (Comparison of the genomes of various T4-like phages)
- Karam, J. D. et al. 1994. Molecular Biology of Bacteriophage T4. ASM Press, Washington, DC. (The second T4 bible, go here, as well as Mosig and Eiserling, 2006, to begin to learn about the biology T4 phage) ISBN 1-55581-064-0
- Eddy, S. R. 1992. Introns in the T-Even Bacteriophages. PhD thesis. University of Colorado at Boulder. (Chapter 3 provides overview of various T4-like phages as well as the isolation of then-new T4-like phages)
- Surdis, T.J "et al" UC Santa Cruz, Nov 1978, "Bacteriophage attachment methods specific to T4", analysis, Overview.
- Mathews, C. K., E. M. Kutter, G. Mosig, and P. B. Berget. 1983. Bacteriophage T4. American Society for Microbiology, Washington, DC. (The first T4 bible; not all information here is duplicated in Karam et al., 1994; see especially the introductory chapter by Doermann for a historical overview of the T4-like phages) ISBN 0-914826-56-5
- Russell, R. L. 1967. Speciation Among the T-Even Bacteriophages. PhD thesis. California Institute of Technology. (Isolation of the RB series of T4-like phages)
- Malys N, Nivinskas R (2009). "Non-canonical RNA arrangement in T4-even phages: accommodated ribosome binding site at the gene 26-25 intercistronic junction". Mol Microbiol. 73 (6): 1115–1127. S2CID 8187771. (rare type of translational regulation characterized in T4)
- Kay D., Fildes P. (1962). "Hydroxymethylcytosine-containing and tryptophan-dependent bacteriophages isolated from city effluents". J. Gen. Microbiol. 27: 143–6. PMID 14454648. (T4-like phage isolation, including that of phage Ox2)