These include an attachment attachment of the bacteriophage to the bacterial cell surface, penetration release of bacteriophage dna, biosynthesis dna replication and the formation of phage proteins, maturation assembling of newly formed phage particles, lysis cell lysis takes place and release of newly formed phages. Lytic or virulent phages are phages, which multiply in bacteria and kill the cell by lysis at the end of the life cycle. Pdf bacteriophages and their structural organisation. Phages as antibiotic alternatives and their use in humans. Bacteriophages, viruses that infect bacteria, may undergo a lytic or lysogenic cycle. Most of the tailed phages possess a holinendolysin system to achieve the release of their. There are five stages in the bacteriophage lytic cycle see figure 1. Under the lysogenic cycle, the cell can either undergo the lytic cycle with a probability of 1. This 54 piece set features bacteriophage replication cycle diagrams lytic and lysogenic, and virus types helical, spherical, polyhedral, complex. The latter is thought to be the main method of viral replication, as it results in. Two major cycles of multiplication of bacteriophages are.
Gene regulation section iii chapter 17 transcriptional regulation in bacteriophage lambda not all bacteriophage. A lysogenic cycle is when a phage injects it genome into the bacteria and it joins with the bacteriasgenome, and a lytic cycle is when a. Induction can be induced artificially using ultraviolet rays or heat treatment. Lytic cycle lysogenic cycle or prophage bacterial chromosome phage phage dna this is a temperate phage classes of animal viruses dsrna no tick fever dna n a rvo ius rhinovirus sars no yes ss rna serves as mrna influenza ebola ssrna yes template ssrna yes hiv retrovirus herpes, chickenpox smallpox no yes ds dna gn ty vir co t exam p. Under the right conditions, the prophage can become active and come back out of the bacterial chromosome, triggering the remaining steps of the lytic cycle dna copying and protein synthesis. The lytic cycle is composed of six different stages. During infection a phage attaches to a bacterium and inserts its genetic material into the cell. Temperate phage reside in the host genome and do not kill the host, whereas lytic phage cause lysis of their hosts.
The action of most of viral genes is to enable the viruses to infect their respective host cells, multiply by using the host machinery such as enzymes and ribosomes and then causing the lysis of cells. Under the lysogenic cycle, the cell can either undergo the lytic cycle with a probability of 1or integrate the prophage into the genome of the host cell with a. Files are available under licenses specified on their. Contemporary phage biology weizmann institute of science. Pdf bacteriophages and their applications researchgate. Specific strains of bacteriophages can only adsorb to specific strain of host bacteria viral specificity. Lysis of bacterial cell envelope and release of progeny phage. Temperate and lytic bacteriophages programmed to sensitize. Gene regulation section iii chapter 17 transcriptional regulation in bacteriophage lambda not all bacteriophage lyse their host bacteria upon infection. The phage involved in this cycle is called temperate phage, the bacterium is the lysogenic strain and the entire process is called lysogeny fig. At the end of the lytic infection cycle, progeny phage particles emerge from the cell in a process that usually involves cell lysis by phage. Pdf structure and morphogenesis of bacteriophage t4. Create a serial dilution of the phage stock and titer the contents. All known phages can be divided in two groups according to the type.
Soon after the nucleic acid is injected, the phage cycle is said to be in eclipse. Genetic recombination occurs between the viral dna and the bacterial genome as the viral dna is inserted into the bacterial chromosome. The host cell breaks open and releases new virus particles. As the lysogenic cycle allows the host cell to continue to survive and reproduce, the virus is replicated in all offspring of the cell. Bacteriophages that replicate through the lytic life cycle are called lytic bacteriophages, adsorption is the attachment sites on the phage adsorb to receptor sites on the host bacterium. The crispr array can be designed with multiple spacers to simultaneously protect against several lytic phages that will be used for selection, thus reducing the occurrence of nonsensitized bacterial mutants that escaped these lytic phages. The set includes 27 png color illustrations, and 27 png blackline versions of.
An example of a bacteriophage known to follow the lysogenic cycle and the lytic cycle is the phage lambda of e. Phages follow two patterns of life cycle as lytic and lysogenic cycle. Lytic cycle lysogenic cycle or prophage bacterial chromosome phage phage dna this is a temperate phage classes of animal viruses dsrna no tick fever dna n a rvo ius rhinovirus sars no yes ss rna. Bacteriophage questions and study guide quizlet flashcards. Difference between lytic and lysogenic cycle of bacteriophage. To infect bacteria a phage injects its dna into the bacteria. Bacterial virus phage bacteriophage general life cycles lytic vs lysogenic ii. Lytic cycle life cycle of viruses that result in the lysis of the host bacterium.
Induction of the vt phage lytic cycle is reca dependent. Attachment the phage attaches itself to the surface of the host cell in order to inject its dna into the cell. Bacteriophage the bacteriophage injects its nucleic acid into the bacterial cell. The cro protein turns off the synthesis of the repressor and thus prevents the establishment of lysogeny. During the process of phage maturation, lysins accumulate in the cytoplasm of infected bacterial cells. As it is clear that some phage infections create lysogens and do not result in a lytic infection, plaque assays may not necessarily detect all infectious phage particles. In the lysogenic cycle, the viral dna circularizes and integrates into the host dna.
Production of phage proteins, dna early replication vs late replication 5. Some phage are also capable of maintaining their chromosome in a stable, silent state within the bacteria. Bacteriophages or phages are viruses that infect bacteria. Comparison of multiplication cycles of bacteriophage and animal viruses. Lytic cycleviruses immediately infect the host cell. Teven phage is a good example of a wellcharacterized class of.
The events of lytic cycle, starting with adsorption, at 37c occurs as below. The lytic cycle is a simple replication cycle comprised of five stepsattachment, penetration, replication, packaging, and burst out. Bacteriophage lytic and lysogenic cycle biology exams 4 u. The effect of multiplicity of infection on the temperateness of. Please use one of the following formats to cite this article in your essay, paper or report. Bacteriophage, also called phage or bacterial virus, any of a group of viruses that infect bacteria. We isolated lytic bacteriophages from fujian and mexico and retained 3 lytic podoviridae bacteriophages which were effective in vitro against 91. In the lytic cycle, l phages replicate rapidly and eventually cause lysis of the host cell. Lyticlysogenic options the process of a phage infecting a bacterium and producing progeny is referred to as a lyticinfection. Entry virus enzyme weakens cell membrane genetic material dna or rna enters host cell. They then destroy, or lyse, the cell, releasing new phage particles.
Soon after the nucleic acid is injected, the phage cycle is said to be in eclipse period. A bacteriophage is of tadpole shape with a head and a tail. Antimicrobial activity of bacteriophage endolysin produced in. Phages that follow lytic cycle are known to be virulent or lytic phages. Attachment sites are plasma membrane proteins and glycoproteins. As the lysogenic cycle allows the host cell to continue to survive and reproduce, the virus is replicated in all offspring of the. Lytic phages take over the machinery of the cell to. The lytic cycle, which is also commonly referred to as the reproductive cycle of the bacteriaphage, is a sixstage cycle.
Lytic cycle causes killing of the bacteria and this property is utilized for the phage therapy. The effect of multiplicity of infection on the temperateness. The bacteriophage lambda is a virus that is parasitic in bacteria, attaching by its tail to the surface to the surface of an li cell and injecting its chromosome into the bacterium to multiply. Reca plays a central role in the sos response of e. At this point they initiate the reproductive cycle, resulting in lysis of the host cell. Jul 01, 2016 the lytic life cycle of a bacteriophage kat movies. Head consists of tightly packed dna covered by a protein coat, while tail is hollow core surrounded by contractile protein sheath. In lysogenic cycle, the lytic vegetative phage becomes integrated with the host cell chromosomes and is converted into prophage without lysis of bacterial cell. The lytic cycle is a simple replication cycle comprised of five stepsattachment, penetration. Reports in the literature have described varied results with the application of lytic bacteriophages on tomatoes. The main difference of these cycles is that in the lytic cycle, bursting or destruction of. The lytic life cycle of a bacteriophage kat movies.
During the lytic cycle of virulent phage, the bacteriophage takes over the cell, reproduces new phages, and destroys the cell. After injecting its nucleic acid into a bacterium, a phage will. Under the right conditions, the prophage can become active. T4 bacteriophage is an appropriate model system for our study because it has been shown to produce consistent plating results and its molecular biology is understood very well. Virulent bacteriophages lyse host cells as a result of expression of the phage genome a. During the eclipse phase, no infectious phage particles can be found either inside or outside the bacterial cell. Teven phage is a good example of a wellcharacterized class of virulent phages. In the lytic cycle, bacteriophage will replicate and cause the bacterial cell to burst, or lyse, to release newly assembled phage. Also, t4 bacteriophage is easy to work with and has a rapid lytic cycle, thus establishing it as a good tool for studying t. Viruses are species specific, but almost every species on earth can be affected by some form of virus. Mar 12, 2001 as it is clear that some phage infections create lysogens and do not result in a lytic infection, plaque assays may not necessarily detect all infectious phage particles. These cycles are the lysogenic life cycle and the lytic life cycle.
Bacteriophage, lytic cycle, viral replication duration. Phage lysozyme opens cell wall, tail sheath contracts to force tail core and dna into cell. Both the lytic and the lysogenic cycle are means in which a virus reproduce. The lytic life cycle of bacteriophages biology libretexts. The lysogenic cycle is less flashy and less gory than the lytic cycle, but at the end of the day, its just another way for the phage to reproduce. Bacteriophage or phage for short is a virus that infects bacteria. Lytic phages take over the machinery of the cell to make phage components. In the lysogenic cycle, bacteriophages reproduce without killing the host. Nucleic acid bacterial dna bacterial host cell bb figure 18. These include an attachment attachment of the bacteriophage to the bacterial cell surface, penetration release of bacteriophage. The prophage may be converted into a virulent vegetative lytic phase spontaneously or by physical and chemical agents uv rays, h 2 0 2, nitrogen mustard. Phage overlay assay for quantification of infectious. The hosts metabolic machinery makes viral nucleic acid and proteins. The mechanism and the evolution of lysogenic cycle are much more complicated than that of the lytic cycle.
Endolysins are bacteriophageencoded peptidoglycan hydrolases, which are synthesized in phageinfected cells at the end of the phage lytic cycle 36. Lysogenic phages incorporate their nucleic acid into the chromosome of the host cell and. Endolysins are bacteriophage encoded peptidoglycan hydrolases, which are synthesized in phageinfected cells at the end of the phage lytic cycle 36. The decision for lambda to enter the lytic or lysogenic cycle when it first enters a cell is determined by the concentration of the repressor and another phage protein called cro in the cell. Lytic cycle replication of new viruses is fast however, the host is also immediately killed preventing the viral genome from passing onto the next generation of host cells lysogenic cycle many more viruses can be made because the viral genome is passed onto future generation of host cells however, replication is. Some phage, like t4, are only capable of lytic growth. Jul 21, 2017 this video will teach you all about the lytic cycle of bacteriophage in hindi. Attachment virus lands on cell membrane virus attaches to a cell receptor no attachment no infection virus acts as a key to the receptor 8. The following article is a discussion of the steps to help you understand this process. Virulent bacteriophages lyse host cells as a result of expression of the. This dissociation is called induction and lytic cycle is followed releasing mature lysogenic phages. The potential of the lytic bacteriophage to disrupt a. This dissociation is called induction and lytic cycle is followed releasing mature lysogenic. Occasionally, integrated viral genome detaches and released into the bacterial cytoplasm.
Apr 04, 2008 in the lytic cycle, l phages replicate rapidly and eventually cause lysis of the host cell. A bacteriophage reproduces by one of two types of life cycles. Bacteriophage life cycle overview lytic steps 1, 2, 5, 6 step 1 step. Lwoff 1953 discovered this type of cycle in lambda w phages that attack e. Also includes forms of influenza transmission airborne and direct. Transcriptional regulation in bacteriophage lambda b m b 400 part four. Lambda consists of two types of life cycles, the lytic and lysogenic. The specificity of every step varies between different types of phages.
1516 1329 514 1017 702 805 536 603 1199 1369 1007 1589 792 972 1366 1043 327 861 245 803 144 796 1032 1556 1063 768 823 41 62 159 1369 749 414 1203 1015 1253 1414 136