Here, the virus integrates its genetic information with that of the host and then becomes . If you are redistributing all or part of this book in a print format, In the lysogenic cycle, phage DNA is incorporated into the host genome, where it is passed on to subsequent generations. It is not clear why the virus stops replicating within the nerve cells and expresses few viral proteins but, in some cases, typically after many years of dormancy, the virus is reactivated and causes a new disease called shingles (Figure 6.13). However, once an infected individual begins exhibiting symptoms, the disease becomes very contagious. There are viruses that are capable of remaining hidden or dormant inside the cell in a process called latency. A prime example of a phage with this type of life cycle is the lambda phage. Specialized transduction occurs at the end of the lysogenic cycle, when the prophage is excised and the bacteriophage enters the lytic cycle. Causes of Ebola. In a lysogenic cycle, the phage genome also enters the cell through attachment and penetration. His condition had deteriorated and additional blood tests confirmed that he has been infected with the Ebola virus. Lytic animal viruses follow similar infection stages to bacteriophages: attachment, penetration, biosynthesis, maturation, and release (see Figure \(\PageIndex{4}\)). A prime example of a phage with this type of life cycle is the lambda phage. Figure 21.2 B. The lytic pathway kills the host cell when newly made bacteriophages are released. In eukaryotic cells, most DNA viruses can replicate inside the nucleus, with an exception observed in the large DNA viruses, such as the poxviruses, that can replicate in the cytoplasm. This occurs through contraction of the tail sheath, which acts like a hypodermic needle to inject the viral genome through the cell wall and membrane. To liberate free phages, the bacterial cell wall is disrupted by phage proteins such as holin or lysozyme. then you must include on every physical page the following attribution: If you are redistributing all or part of this book in a digital format, Microbiology Lecture Outline Chapter 13 Viruses I: Acellular Plant viruses may have a narrow or broad host range. Ebola - spread by blood and body fluids, reservoir unknown; . Viral contents are released into the cell, where viral enzymes convert the single-stranded RNA genome into DNA and incorporate it into the host genome. The growth curve of bacteriophage populations is a, Bacteriophages transfer genetic information between hosts using either. It is a one-dose shot that protects against the variant of the Ebola virus that has caused the most serious outbreak so far. The DNA can then recombine with host chromosome, giving the latter new characteristics. Additionally, Ebola can also be contracted through exposure to contaminated surfaces, needles or medical equipment. Once inserted, the viral genome is known as a prophage. It serves as the template for the new viral particles. This corresponds, in part, to the eclipse period in the growth of the virus population. During the lytic cycle of virulent phage, the bacteriophage takes over the cell, reproduces new phages, and destroys the cell. Many viruses are host specific, meaning they only infect a certain type of host; and most viruses only infect certain types of cells within tissues. New nucleocapsids accumulate near or around the nucleus and begin moving to the host cell membrane, where they can "bud off." For additional information about Ebola, please visit the CDC website. Once new virus particles are replicated, the increase in the number of viral proteins signals the change from translation to replication. During the maturation phase, new virions are created. Ebola, also known as Ebola virus disease (EVD), is a severe and often deadly illness caused by the Ebola virus. There are occasional outbreaks of Ebola, and they mostly occur in Africa. Environmental stressors such as starvation or exposure to toxic chemicals may cause the prophage to be excised and enter the lytic cycle. Generalized transduction occurs when a random piece of bacterial chromosomal DNA is transferred by the phage during the lytic cycle. In the lysogenic cycle, the DNA is only replicated, not translated into proteins. The Zaire ebolavirus, more commonly known as the Ebola virus, was linked to severe EVD outbreaks such as the 1976 viral hemorrhagic fever outbreak in Sudan and Congo. After replication and assembly of new virus particles, viruses are released from host cells. As the bacterium replicates its chromosome, it also replicates the phages DNA and passes it on to new daughter cells during reproduction. Despite its virulence, Ebola has not spread in Europe and the United States. No approved treatments or vaccines for Ebola are available. If a virus has a +ssRNA genome, it can be translated directly to make viral proteins. Plant viruses may be enveloped or non-enveloped. The Ebola virus begins. Though both pose large threats to human health, one of the viruses that encompass both the lytic cycle as well as the lysogenic cycle is HIV/AIDS. This specificity is called a tissue tropism. Some viruses reproduce using both methods, while others only use the lytic cycle. Transduction occurs when a bacteriophage transfers bacterial DNA from one bacterium to another during sequential infections. As the cell becomes overcrowded with viruses, the original virus releases enzymes to break the cell wall, causing the cell to burst and release new viruses. The lysogenic cycle is a method by which a virus can replicate its DNA using a host cell. The efficacy of the drugs was evaluated during the 2018-2020 Ebola outbreak in the Democratic Republic of Congo. Once a hospital realizes a patient like Duncan is infected with Ebola virus, the patient is immediately quarantined, and public health officials initiate a back trace to identify everyone with whom a patient like Duncan might have interacted during the period in which he was showing symptoms. The burst size is the maximum number of virions produced per bacterium. - Definition, Structure & Function, Shapes of a Virus: Helical, Icosahedral, Prolate, Complex & Enveloped, Classification of Viruses: Viral Genome and Replication Scheme, The Life Cycle of a Virus: How Viruses Live, Attack & Replicate, Lytic Cycle of a Virus: Definition & Steps, Lysogenic Cycle of a Virus: Definition & Steps, Ebola Virus Life Cycle: Definition & Stages, How Viruses Mutate: Antigenic Drift and Antigenic Shift, Prentice Hall Biology: Online Textbook Help, Praxis Family and Consumer Sciences (5122) Prep, College Chemistry: Homework Help Resource, SAT Subject Test Chemistry: Practice and Study Guide, ILTS Science - Environmental Science (112): Test Practice and Study Guide, Human Anatomy & Physiology: Help and Review, FTCE Middle Grades General Science 5-9 (004) Prep, Environmental Science 101: Environment and Humanity, Potassium Bromide: Formula & Side Effects, What is a Benign Tumor? Symptoms of Ebola. Given the great suffering and high mortality rates, it is fair to ask whether unregistered and untested medications are better than none at all. Ebola is incurable and deadly. Ebola undergoes a lytic cycle a mechanism of virus replication that uses the host cell to produce new copies of viral particles and destroy the host cell's DNA. An alternative mechanism for viral nucleic acid synthesis is observed in the retroviruses, which are +ssRNA viruses (see Figure 6.12). The ssDNA is then made into dsDNA, which can integrate into the host chromosome and become a permanent part of the host. The integrated viral genome is called a provirus. The genus Ebolavirus consists of six species, but only four have been known to cause human disease: Zaire ebolavirus, Sudan ebolavirus, Tai Forest ebolavirus, and Bundibugyo ebolavirus. However, most plant viruses do not have a DNA genome; the majority have a +ssRNA genome, which acts like messenger RNA (mRNA). As an Amazon Associate we earn from qualifying purchases. The virus now can remain in the host for a long time to establish a chronic infection. Some kinds of bacteriophages even go through both cycles. This, along with Duncans initial misdiagnosis, made it clear that US hospitals needed to provide additional training to medical personnel to prevent a possible Ebola outbreak in the US. This page titled 6.2: The Viral Life Cycle is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by OpenStax via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request. During the lysogenic cycle, instead of killing the host, the phage genome integrates into the bacterial chromosome and becomes part of the host. The hospital continued to treat Duncan, but he died several days after being admitted. I feel like its a lifeline. The first proposed treatment focuses on inhibiting the Ebola replication process using small fragments of genetic material called small-interfering RNAs (siRNAs), designed to match a particular piece of the virus' RNA. During the process of excision from the host chromosome, a phage may occasionally remove some bacterial DNA near the site of viral integration. On September 15, nine days before he showed up at the hospital in Dallas, Duncan had helped transport an Ebola-stricken neighbor to a hospital in Liberia. The RdRP is brought in by the virus and can be used to make +ssRNA from the original ssRNA genome. are licensed under a, Unique Characteristics of Prokaryotic Cells, Unique Characteristics of Eukaryotic Cells, Prokaryote Habitats, Relationships, and Microbiomes, Nonproteobacteria Gram-Negative Bacteria and Phototrophic Bacteria, Isolation, Culture, and Identification of Viruses, Using Biochemistry to Identify Microorganisms, Other Environmental Conditions that Affect Growth, Using Microbiology to Discover the Secrets of Life, Structure and Function of Cellular Genomes, How Asexual Prokaryotes Achieve Genetic Diversity, Modern Applications of Microbial Genetics, Microbes and the Tools of Genetic Engineering, Visualizing and Characterizing DNA, RNA, and Protein, Whole Genome Methods and Pharmaceutical Applications of Genetic Engineering, Using Physical Methods to Control Microorganisms, Using Chemicals to Control Microorganisms, Testing the Effectiveness of Antiseptics and Disinfectants, History of Chemotherapy and Antimicrobial Discovery, Fundamentals of Antimicrobial Chemotherapy, Testing the Effectiveness of Antimicrobials, Current Strategies for Antimicrobial Discovery, Virulence Factors of Bacterial and Viral Pathogens, Virulence Factors of Eukaryotic Pathogens, Major Histocompatibility Complexes and Antigen-Presenting Cells, Laboratory Analysis of the Immune Response, Polyclonal and Monoclonal Antibody Production, Anatomy and Normal Microbiota of the Skin and Eyes, Bacterial Infections of the Skin and Eyes, Protozoan and Helminthic Infections of the Skin and Eyes, Anatomy and Normal Microbiota of the Respiratory Tract, Bacterial Infections of the Respiratory Tract, Viral Infections of the Respiratory Tract, Anatomy and Normal Microbiota of the Urogenital Tract, Bacterial Infections of the Urinary System, Bacterial Infections of the Reproductive System, Viral Infections of the Reproductive System, Fungal Infections of the Reproductive System, Protozoan Infections of the Urogenital System, Anatomy and Normal Microbiota of the Digestive System, Microbial Diseases of the Mouth and Oral Cavity, Bacterial Infections of the Gastrointestinal Tract, Viral Infections of the Gastrointestinal Tract, Protozoan Infections of the Gastrointestinal Tract, Helminthic Infections of the Gastrointestinal Tract, Circulatory and Lymphatic System Infections, Anatomy of the Circulatory and Lymphatic Systems, Bacterial Infections of the Circulatory and Lymphatic Systems, Viral Infections of the Circulatory and Lymphatic Systems, Parasitic Infections of the Circulatory and Lymphatic Systems, Fungal and Parasitic Diseases of the Nervous System, Fundamentals of Physics and Chemistry Important to Microbiology, Taxonomy of Clinically Relevant Microorganisms. Retrovirus: Definition, Life Cycle & Example, Psychological Research & Experimental Design, All Teacher Certification Test Prep Courses, The Central Dogma of Biology & Protein Synthesis, What Are Viruses? Several viruses in the filovirus classification are lytic, including: Filovirus Strains: Marburg Ebola: Reston ebolavirus Tai Forest ebolavirus Bundibugyo ebolavirus Sudan ebolavirus Zaire ebolavirus. After induction has occurred the temperate phage can proceed through a lytic cycle and then undergo lysogeny in a newly infected cell (see Figure 6.8). The one-step multiplication curve for a bacteriophage population follows three steps: 1) inoculation, during which the virions attach to host cells; 2) eclipse, during which entry of the viral genome occurs; and 3) burst, when sufficient numbers of new virions are produced and emerge from the host cell. Capable of remaining hidden or dormant inside the cell, reproduces new phages, destroys. 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