Multiple choice questions on bacteriophage mcq biology. Typically, viruses can undergo two types of dna replication. Lysogenic strains are also called as a temperate phages b avirulant phages c both a and b d none of these learn more. It is a bacterial virus, or bacteriophage, that infects the bacterial species escherichia coli. Lytic and lysogenic life cycle of a phage intra cellular multiplication of the phage ends in the lysis of the host bacterium and the release of progeny virions. However, in both cases the virus phage replicates using the host dna machinery. Similar to the lytic cycle, it begins with the attachment and penetration of the virus. Lysogenic cycle wikimili, the best wikipedia reader. Clipping is a handy way to collect important slides you want to go back to later. Now customize the name of a clipboard to store your clips. After injection, the linear phage dna is circularized. Both the lytic and the lysogenic cycle are means in which a virus reproduce. There are two types of life cycles as far as viruses are concenrned. The cro protein turns off the synthesis of the repressor and thus prevents the establishment of lysogeny.
In the case of cloning, the lysogenic cycle is most important, because, the phage dna can carry a specific gene that is further incorporated in the host genome. Lysogenic phages incorporate their nucleic acid into the chromosome of the host cell and. 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. Virus reproduction that destroys its host cell to release virion. The lysogenic cycle figure 3, sometimes referred to as temperate or nonvirulent infection, does not kill the host cell, instead using it as a refuge where it exists in a dormant state.
Soon after the nucleic acid is injected, the phage cycle is said to be in eclipse period. Alternatively, they may enter a dormant state, known as the lysogenic cycle, within the host cell if conditions are favorable. Fish, a method to visualize intracellular and free. The four different phages carried by the respective lysogenic strains were inactivated to a greater or lesser extent by phagolessin a58, but there was no correlation between such sensitivity on the part of the carried phage and inducibility of the particular lysogenic strain. Lytic vs lysogenic cycle 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. Lambda phage study guide by emgent includes 37 questions covering vocabulary, terms and more. History of lambda phagein 1950, esther lederberg, an american microbiologist, was performing experiments on e. In the lytic cycle, phage genes are expressed and dna is replicated resulting in production of several phage particles. Jul 14, 2014 lambda phage is a temperate bacteriophage that infects escherichia coliit have alternative replication pathways. Lytic cycle or lytic phages called as virulent phages multiplies inside the host bacterium and new viral particles comes out by lysing or by rupturing the host bacterial cell wall. At upper left, a bacteriophage lambda virion has attached to the bacterial cell wall. During the eclipse phase, no infectious phage particles can be found either inside or outside the bacterial cell. Coli is called lambda phage and has a great potential as a cloning vector.
Lytic and lysogenic cycles of lambda phage when lambda phage infects a bacterium, eg e. She happened to observe streaks of mixtures of two types of e. In general the life cycle of most phages at 37c varies between 22 and 60 minutes. This dissociation is called induction and lytic cycle is followed releasing mature lysogenic phages.
Once the viral dna has been inserted into the cell, the host is. A phage that only has a lytic cycle t4 temperate phage. Following the injection of the phage dna into the host cell, it integrates itself into the host genome. At least one of these results, in 2015, refers, however, to a lytic or lysogenic phage life cycle emphasis added. Bacteriophage lambda can reproduce in two alternative modes of growth. Our mission is to provide a free, worldclass education to anyone, anywhere. Lytic cycle is the process where the virulent phages multiply in bacteria and then cause the death of the bacteria by lysis at the end of the cycle. In the lysogenic mode, the phage infects a bacterial cell, incorporates its dna into the chromosome of the host cell, and remains. Escherichia coli, bacteriophage lambda, lysis lysogeny, gene. Usually, a lytic cycle ensues, where the lambda dna is replicated and new phage particles are produced within the cell. Quizlet flashcards, activities and games help you improve your grades.
During the lysogenic cycle, instead of killing the host, the phage genome integrates into the bacterial chromosome and becomes part of the host. Pdf the lysislysogeny decision of bacteriophage lambda lambda is a paradigm for developmental genetic networks. The wild type of this virus has a temperate life cycle that allows it to either reside within the genome of its host through lysogeny or enter into a lytic phase, during. Lysogenic phages incorporate their nucleic acid into the chromosome of the host cell. Lysis of bacterial cell envelope and release of progeny phage. Lytic and lysogenic cycles are two different methods of viral replication. Temperate phages are basically bacteriophages which can choose between a lytic.
During infection, the phage particle recognizes and binds to its host, e. Lytic vs lysogenic understanding bacteriophage life cycles. The lysogenic cycle is a method by which a virus can replicate its dna using a host cell. Phages that replicate only via the lytic cycle are known as virulent phages. Nov 30, 20 contents introduction how genome is transferred lytic cycle and lysogenic cycle life cycle lytic or lysogenic. The lambda infected bacterium then exhibits either a lytic cycle or a lysogenic cycle. In the lytic cycle, the viral dna exists as a separate free floating molecule within the bacterial cell, and replicates separately from the host bacterial dna, whereas in the lysogenic cycle, the viral dna is located within the host dna. The lambda phage will remain in the lysogenic state if ci proteins predominate, but will be transformed into the lytic cycle if cro proteins predominate. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Progeny assembles in phage particle and gets released. Contents introduction how genome is transferred lytic cycle and lysogenic cycle life cycle lytic or lysogenic.
Temperate phages such as lambda phage can reproduce using both the lytic and the lysogenic cycle. Explain the regulation of gene expression in the lytic and. Sep 25, 2018 the creation of multiple copies of the virus is done as the host cell divides itself and the phage dna is passed on to the daughter cells. Since jacob and monod proposed the idea of operon control for phages, the genetic system of the. The phage dna finally released from the host cell by entering into the lytic cycle. The lytic cycle produces progeny phage particles, and is thus the more common cycle that comes after. The lysogenic bacteria bear the two key features, immunity to superinfection by other phage. Bacteriophage lytic and lysogenic cycles from clep biology. While the lytic cycle is common to both animal viruses and bacterial phages, the lysogenic cycle is more commonly found in animal viruses. The word lytic literally means disintegration or breakdown.
In lytic cycle the subsequent steps are synthesis of phage components, assembly, maturation and release. A discussion of the properties of the phage in the lysogenic condition will follow, based on published data and on some unpublished results. Lytic and lysogenic life cycle of a phage brainkart. Lambda phage is a temperate bacteriophage that infects escherichia coli it have alternative replication pathways. Diversity of phage infection types and associated terminology. Lytic vs lysogenic cycle two modes of multiplication cycle in bacteriophages namely lytic cycle and lysogenic cycle.
The phage infects a bacterium and inserts its dna into the bacterial. All except one gene present in the phage is turned off, hence causing one phage chromosome, the prophage, to become as part of the host chromosomes, hence making a. Attachment the phage attaches itself to the surface of the host cell in order to inject its dna into the cell. Bacteriophages are viruses that infect and replicate within a bacterium. View lytic and lysogenic cycle ppts online, safely and virus free. A phage with both lytic and lysogenic stages lambda immunity.
Lytic or virulent phages are phages, which multiply in bacteria and kill the cell by lysis at the end of the life cycle. A cell with a lysogenic phage cannot be superinfected with additional phage of the same type. Lysogeny is characterized by integration of the bacteriophage nucleic acid into the host bacteriums genome or formation of a circular replicon in the bacterial cytoplasm. Lytic or lysogenic oxford academic journals oxford university. Lysogeny, or the lysogenic cycle, is one of two cycles of viral reproduction lysogeny is. Lytic phages take over the machinery of the cell to make phage components. Finally, the process of phage multiplication in lysogenic bacteria will be compared with the process of phage. The lytic cycle results in the destruction of the infected cell and its membrane. The phage then injects its dna red rope like object into the bacterium. Virus infection changes from a lysogenic cycle to a productive cycle. The lytic cycle ends with lysis of li cells and liberation of phage particles. Apr 20, 2014 this lamda phage lecture explains the lysogenic cycle of lamda bacteriophage.
Insertion and excision of bacteriophage into its host genome. Lysogenic phages incorporate their nucleic acid into the chromosome of the host cell and replicate with it as a read more. What two genes dictate if lambda goes into lytic cycle or lysogenic cycle. The viral dna arriving in the cell is linear but the free ends soon join up to make a circle which then supercoils into a bundle. Phages that replicate only via the lytic cycle are known as virulent phages while phages that replicate using both lytic and lysogenic cycles are known as temperate phages. Escherichia coli, bacteriophage lambda, lysislysogeny, gene. In the lytic mode, the phage infects a bacterial cell, reproduces many copies of itself, lyses the host cell, and circulates through the environment to infect another host cell. This bacteriophage lecture explains the structure and properties of bacteriophage lamda.
Soon after the discovery of bacterial viruses bacteriophage, it was observed that certain phage were purely lytic, resulting in clear plaques of complete host cell lysis, while others caused cloudy or turbid plaques of incomplete lysis. The following are the steps of the lysogenic cycle. Though most temperate phages during productive cycles release virions via lysisthat is, during lytic cycles nonetheless in all likelihood the intended use of lytic in lytic or lysogenic as descriptions of phage types is as shorthand for the v b f i phages, that is, lytic, nontemperate phages. In the lytic phase, the phage genes for reproduction are active induced. 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. In the lytic cycle figure 2, sometimes referred to as virulent infection, the infecting phage ultimately kill the host cell to produce many of their own progeny. Occasionally, integrated viral genome detaches and released into the bacterial cytoplasm. Persistence describes the prophage stage during the lysogenic cycle, replication describes the phage genome state during productive cycles and release refers not just to the means by which progeny phage virions transition from the intracellular to extracellular state but also the impact of productive cycles on the phage infected bacterium i. Induction can be induced artificially using ultraviolet rays or heat treatment.
Enterobacteria phage lambda an overview sciencedirect. They then destroy, or lyse, the cell, releasing new phage particles. An example of a bacteriophage known to follow the lysogenic cycle and the lytic cycle is the phage lambda of e. The ci dimer may bind to any of three operators, o r 1, o r 2, and o r 3, in the order o r 1 o r 2 o r 3. Here, the virus integrates its genetic information with that of the host and then becomes dormant, letting the host multiply and continue its normal activities. Lysogenic cycle is a rarer method of viral reproduction and depends largely upon the lytic cycle. The main difference of these cycles is that in the lytic cycle, bursting or destruction of the host cell inevitably occurs whereas in the lysogenic cycle, the phage can replicate without harming their host. Via the lysogenic cycle, the bacteriophages genome is not expressed and is instead integrated into the bacterias genome to form the prophage. In the lysogenic cycle, phage nucleic acid will integrate into the bacterial.
Depending on the life cycle, phages can either by lytic virulent or lysogenic temperate. At this point they initiate the reproductive cycle, resulting in lysis of the host cell. Some of the spontaneously induced cells enter the lytic cycle abortively, lose the prophage curing, and. Lysogenic cycle definition and steps biology dictionary. In the lysogenic cycle, the dna is only replicated, not translated into proteins. In lysogenic cycle the host dna is not hydrolysed but in lytic cycle the host dna is hydrolysed in the lytic phase. While they are different, they can be interchangeable or the replication can involve both methods in separate phases. Lytic and lysogenic cycles of lambda phage term paper. The lytic cycle, which is also commonly referred to as the reproductive cycle of the bacteriaphage, is a sixstage cycle. In this condition the bacterium continues to live and reproduce normally. While lytic phages kill the cells they infect, temperate phages establish a persistent infection of the cell without killing it. Lytic phage that is able to display lysogenic cycles. The life cycle of bacteriophage lambda serves as a simplified paradigm for. Lysogeny, or the lysogenic cycle, is one of two cycles of viral reproduction the lytic cycle being the other.
The lytic cycle is known as the active cycle, whereas the lysogenic cycle is the dormant phase of the virus. The immunity to superinfection and establishment of lysogeny in lysogens is conferred in the presence of. A prime example of a phage with this type of life cycle is the lambda phage. The infection cycle of lambda phage is an excellent example of a lysogenic cycle. Phage which displays only lytic cycles no chronic or lysogenic cycles. Bacteriophage lytic and lysogenic cycle biology exams 4 u. Doc lysogenic vs lytic cycle of lambda phage akbar. However, the viral dna has the mechanism to convert from a lysogenic life cycle to a lytic cycle at any given point a process known as induction. In the lytic cycle, a phage acts like a typical virus. In 1950, esther lederberg, an american microbiologist, was performing experiments on e. As the lysogenic cycle allows the host cell to continue to survive and reproduce, the virus is reproduced in all of the cells offspring.
The major difference between the two is the fact that in lytic cycle the v. Meanwhile, the lysogenic cycle is where the temperate phages the virus in which can either multiply through lytic cycle or enter a dormant state in the cell. The induction of the lytic cycle in lysogenic bacteria by. Nov 19, 2019 at this point they initiate the reproductive cycle, resulting in lysis of the host cell. In a lysogenic cycle, the phage genome also enters the cell through attachment and penetration. Start studying lytic and lysogenic cycle bacteriophage. Binding of a ci dimer to o r 1 enhances binding of a second ci dimer to o r 2, an. In the lysogenic state, the prophage genome is inactive repressed. The life cycle of lambda phages is controlled by ci and cro proteins. The life cycle of upon infection, the phage can pursue lytic growth or lysogeny. Lamda phage replication cycle hd animation youtube. Both cycles undergo a similar initial infection, when the phage binds to the host bacteriums surface. In this model, the cell surface is divided into receptorrich and receptorfree regions.
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