Multiplication of Bacteriophages (Lytic Cycle)Amy Warenda Czura, Ph.D.1SCCC BIO244 Chapter 13 HandoutThe Lysogenic CycleAmy Warenda Czura, Ph.D.2SCCC BIO244 Chapter 13 Handout2. Penetration / Entry:A. Non-enveloped viruses are endocytosed into a vesicleB. Enveloped viruses enter by fusion3. Uncoating: enzymesdegrade capsid releasingnucleic acid5. Maturation and Release:capsule and nucleic acidassemble into virionA. Enveloped: buds out ofcell taking membrane, cellsurvivesB. Non-enveloped: rupturesout of cell membrane, celldies.1. Attachment: virusattachment sites bindhost receptor proteinson plasma membrane 2A2B135A5B4AMultiplication Of Animal Viruses4B4. BiosynthesisA. DNA viruses: DNAreplicated in nucleus, proteinmade in cytoplasm, virionassembly in nucleusB. RNA viruses: RNA andprotein made in cytoplasm,virions assemble in cytoplasmC. Retroviruses: reversetranscribe dsRNA genome todsDNA, DNA integrated intohost genome as provirus,provirus remains latent or isexpressed to create virions in thecytoplasm4CA. Non-enveloped:viral enzymes forescape from vesicleB. Enveloped: hostcytoplasm enzymesAmy Warenda Czura, Ph.D.3SCCC BIO244 Chapter 13 HandoutComparison of Bacteriophage and Animal Virus Life CyclesStage Phage Animal Virus Attachment Tail fibers attach to cell wall proteins Pentons, spikes or capsid proteins attach to plasma membrane proteins or glycoproteins Penetration / Entry Viral DNA is injected into the host cell Capsid enters intact by endocytosis or fusion Uncoating Not required Host or viral enzymes digest capsid Biosynthesis & Maturation In cytoplasm DNA viruses: in nucleus RNA viruses: in cytoplasm Chronic infection? Lysogeny (prophage) Latency or cancer (provirus) Release Host cell lysed by lysozyme Enveloped: bud out through membrane and host cell remains intact Nonenveloped: rupture cell membrane and host cell dies Amy Warenda Czura, Ph.D.4SCCC BIO244 Chapter 13
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