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. Bacteriophage questions and study guide quizlet flashcards. Bacteriophages or phages are viruses that infect bacteria. Specific strains of bacteriophages can only adsorb to specific strain of host bacteria viral specificity. Temperate phage reside in the host genome and do not kill the host, whereas lytic phage cause lysis of their hosts. 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. This dissociation is called induction and lytic cycle is followed releasing mature lysogenic phages. The lytic cycle is composed of six different stages. Transcriptional regulation in bacteriophage lambda b m b 400 part four. Also includes forms of influenza transmission airborne and direct.
Bacteriophage or phage for short is a virus that infects bacteria. The cro protein turns off the synthesis of the repressor and thus prevents the establishment of lysogeny. 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. 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 lytic cycle, which is also commonly referred to as the reproductive cycle of the bacteriaphage, is a sixstage cycle. Phages follow two patterns of life cycle as lytic and lysogenic cycle. 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. To infect bacteria a phage injects its dna into the bacteria. The lytic cycle is a replication process carried out by a virus within a bacterial cell.
Some phage, like t4, are only capable of lytic growth. Comparison of multiplication cycles of bacteriophage and animal viruses. Bacteriophage lytic and lysogenic cycle biology exams 4 u. Most of the tailed phages possess a holinendolysin system to achieve the release of their. Temperate and lytic bacteriophages programmed to sensitize. Genetic recombination occurs between the viral dna and the bacterial genome as the viral dna is inserted into the bacterial chromosome. T4 bacteriophage average burst size varies with escherichia. Teven phage is a good example of a wellcharacterized class of. 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.
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. This dissociation is called induction and lytic cycle is followed releasing mature lysogenic. The host cell breaks open and releases new virus particles. During the eclipse phase, no infectious phage particles can be found either inside or outside the bacterial cell. In the lytic cycle, bacteriophage will replicate and cause the bacterial cell to burst, or lyse, to release newly assembled phage. Attachment the phage attaches itself to the surface of the host cell in order to inject its dna into the cell. Two major cycles of multiplication of bacteriophages are. Bacteriophage, also called phage or bacterial virus, any of a group of viruses that infect bacteria.
Lytic and lysogenic infection of diverse escherichia coli and. The lytic life cycle of a bacteriophage kat movies. Files are available under licenses specified on their. Occasionally, integrated viral genome detaches and released into the bacterial cytoplasm. Under the lysogenic cycle, the cell can either undergo the lytic cycle with a probability of 1. 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. Jul 21, 2017 this video will teach you all about the lytic cycle of bacteriophage in hindi. As the lysogenic cycle allows the host cell to continue to survive and reproduce, the virus is replicated in all offspring of the. Virulent bacteriophages lyse host cells as a result of expression of the phage genome a. Attachment sites are plasma membrane proteins and glycoproteins. The lytic cycle involves the reproduction of viruses using a host cell to manufacture more viruses. Lwoff 1953 discovered this type of cycle in lambda w phages that attack e.
The following article is a discussion of the steps to help you understand this process. The effect of multiplicity of infection on the temperateness of. Pdf structure and morphogenesis of bacteriophage t4. Evolvement of resistance to lytic phages can likewise be minimized by using a mixture of lytic phages.
Nucleic acid bacterial dna bacterial host cell bb figure 18. Phages that follow lytic cycle are known to be virulent or lytic phages. Induction can be induced artificially using ultraviolet rays or heat treatment. Apr 04, 2008 in the lytic cycle, l phages replicate rapidly and eventually cause lysis of the host cell. In lysogenic cycle, the lytic vegetative phage becomes integrated with the host cell chromosomes and is converted into prophage without lysis of bacterial cell. A bacteriophage is of tadpole shape with a head and a tail. Lytic phages take over the machinery of the cell to. Jul 01, 2016 the lytic life cycle of a bacteriophage kat movies. At this point they initiate the reproductive cycle, resulting in lysis of the host 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.
Also, t4 bacteriophage is easy to work with and has a rapid lytic cycle, thus establishing it as a good tool for studying t. Reca plays a central role in the sos response of e. Phages as antibiotic alternatives and their use in humans. Bacteriophage, lytic cycle, viral replication duration. In the lytic cycle, l phages replicate rapidly and eventually cause lysis of the host cell. Some phage are also capable of maintaining their chromosome in a stable, silent state within the bacteria. Head consists of tightly packed dna covered by a protein coat, while tail is hollow core surrounded by contractile protein sheath. The mechanism and the evolution of lysogenic cycle are much more complicated than that of the lytic cycle. During the process of phage maturation, lysins accumulate in the cytoplasm of infected bacterial cells. Pdf bacteriophages and their applications researchgate. Lytic cycle life cycle of viruses that result in the lysis of the host bacterium. Jan 11, 2012 07 lytic vs lysogenic cycle 41,476 views. Endolysins are bacteriophage encoded peptidoglycan hydrolases, which are synthesized in phageinfected cells at the end of the phage lytic cycle 36. Phage overlay assay for quantification of infectious.
Soon after the nucleic acid is injected, the phage cycle is said to be in eclipse period. As the lysogenic cycle allows the host cell to continue to survive and reproduce, the virus is replicated in all offspring of the cell. Pdf bacteriophages and their structural organisation. Lytic cycle causes killing of the bacteria and this property is utilized for the phage therapy. The specificity of every step varies between different types of phages.
The lytic cycle is a simple replication cycle comprised of five stepsattachment, penetration. These cycles are the lysogenic life cycle and the lytic life cycle. Bacteriophage the bacteriophage injects its nucleic acid into the bacterial cell. During the lytic cycle of virulent phage, the bacteriophage takes over the cell, reproduces new phages, and destroys the cell. The main difference of these cycles is that in the lytic cycle, bursting or destruction of. After injecting its nucleic acid into a bacterium, a phage will.
The events of lytic cycle, starting with adsorption, at 37c occurs as below. 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. 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. All known phages can be divided in two groups according to the type. They then destroy, or lyse, the cell, releasing new phage particles. Phage lysozyme opens cell wall, tail sheath contracts to force tail core and dna into cell. Lysis of bacterial cell envelope and release of progeny phage. Compare and contrast the lytic and lysogenic life cycles. Difference between lytic and lysogenic cycle of bacteriophage.
Lyticlysogenic options the process of a phage infecting a bacterium and producing progeny is referred to as a lyticinfection. The lytic life cycle of bacteriophages biology libretexts. Antimicrobial activity of bacteriophage endolysin produced in. Production of phage proteins, dna early replication vs late replication 5. 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. The effect of multiplicity of infection on the temperateness. In the lysogenic cycle, the viral dna circularizes and integrates into the host dna. 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.
Induction of the vt phage lytic cycle is reca dependent. The potential of the lytic bacteriophage to disrupt a. 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. Virulent bacteriophages lyse host cells as a result of expression of the. Teven phage is a good example of a wellcharacterized class of virulent phages. Endolysins are bacteriophageencoded peptidoglycan hydrolases, which are synthesized in phageinfected cells at the end of the phage lytic cycle 36. During infection a phage attaches to a bacterium and inserts its genetic material into the cell. 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.
An example of a bacteriophage known to follow the lysogenic cycle and the lytic cycle is the phage lambda of e. 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. Both the lytic and the lysogenic cycle are means in which a virus reproduce. Soon after the nucleic acid is injected, the phage cycle is said to be in eclipse. We isolated lytic bacteriophages from fujian and mexico and retained 3 lytic podoviridae bacteriophages which were effective in vitro against 91. Lysogenic phages incorporate their nucleic acid into the chromosome of the host cell and. There are five stages in the bacteriophage lytic cycle see figure 1. Bacteriophages, viruses that infect bacteria, may undergo a lytic or lysogenic cycle. Please use one of the following formats to cite this article in your essay, paper or report. Lambda consists of two types of life cycles, the lytic and lysogenic. 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. 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.
Gene regulation section iii chapter 17 transcriptional regulation in bacteriophage lambda not all bacteriophage. Under the right conditions, the prophage can become active. The hosts metabolic machinery makes viral nucleic acid and proteins. 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. Lytic phages take over the machinery of the cell to make phage components. A bacteriophage reproduces by one of two types of life cycles.
Gene regulation section iii chapter 17 transcriptional regulation in bacteriophage lambda not all bacteriophage lyse their host bacteria upon infection. Bacteriophage life cycle overview lytic steps 1, 2, 5, 6 step 1 step. Contemporary phage biology weizmann institute of science. Lytic cycleviruses immediately infect the host cell. The set includes 27 png color illustrations, and 27 png blackline versions of.
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. Also includes forms of influenza transmission airborne and. Create a serial dilution of the phage stock and titer the contents. This 54 piece set features bacteriophage replication cycle diagrams lytic and lysogenic, and virus types helical, spherical, polyhedral, complex. Entry virus enzyme weakens cell membrane genetic material dna or rna enters host cell. The action of most of viral genes is to enable the viruses to infect their respective host cells.
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