Viruses: Morphology and Bacteriophage Life CycleVirusesHelical VirusesPolyhedral (Isometric) VirusesSome Viruses Have a Phospholipid EnvelopeComplex VirusesViral TaxonomySlide 8Growing VirusesSlide 10Virus IdentificationSlide 12PowerPoint PresentationSlide 14Slide 15The Lytic and Lysogenic CyclesSlide 17Viruses: Morphology and Bacteriophage Life CycleFigure 13.1What is a Virus and How is it Built?•Obligate intracellular parasites•Morphology of a Virion•Size (1/1000 to 1/4 size of bacterium)•Composition•RNA vs DNA•Capsid, envelope, spikes •Shapes•helical, polyhedral (isometric) , complex•Host ranges and grouping of viruses•Bacterial, plant, animal viruses•Propagation and study of viruses•Bacteriophage plaques on a lawn•Animal virus propagation•Identifying virusesBacterial Virus Life Cycles (DNA viruses)•Lytic Cycle (e.g. T4 bacteriophage)•Attachment•Penetration/Entry•Biosynthesis•Assembly•Lysis/Release•Lysogenic Life CycleViruses cannot reproduce outside of a cell. They are extremely small and come in three different shapes. They are very specific for their hosts. In the lytic cycle of bacteriophages, they enter, reproduce, and leave.VirusesFigure 13.1Helical VirusesFigure 13.4a, bPolyhedral (Isometric) VirusesFigure 13.2a, bSome Viruses Have a Phospholipid EnvelopeMembrane proteinsform “spikes” that stick out from membraneComplex VirusesFigure 13.5aViral Taxonomy•“Family” names end in -viridae•“Genus” names end in -virus •Viral species: A group of viruses sharing the same genetic information and ecological niche (host). Common names are used for species•Subspecies are designated by a number•Herpesviridae•Herpesvirus•Human herpes virus 1, HHV 2, HHV 3•Retroviridae•Lentivirus•Human Immunodeficiency Virus 1, HIV 2Viruses: Morphology and Bacteriophage Life CycleFigure 13.1What is a Virus and How is it Built?•Obligate intracellular parasites•Morphology of a Virion•Size (1/1000 to 1/4 size of bacterium)•Composition•RNA vs DNA•Capsid, envelope, spikes •Shapes•helical, polyhedral, complex•Host ranges and grouping of viruses•Bacterial, plant, animal viruses•Propagation and study of viruses•Bacteriophage plaques on a lawn•Animal virus propagation•Identifying virusesBacterial Virus Life Cycles (DNA viruses)•Lytic Cycle (e.g. T4 bacteriophage)•Attachment•Penetration/Entry•Biosynthesis•Assembly•Lysis/ReleaseViruses cannot reproduce outside of a cell. They are extremely small and come in three different shapes. They are very specific for their hosts. In the lytic cycle of bacteriophages, they enter, reproduce, and leave.Growing Viruses•Viruses must be grown in living cells.•Bacteriophages form plaques on a lawn of bacteria.Figure 13.6•Animal viruses may be grown in living animals, or in embryonated eggs, or in tissue cultureGrowing Viruses•Animal and plants viruses may be grown in cell culture.•Continuous cell lines may be maintained indefinitely.Figure 13.8•Cytopathic effects•Serological tests•Detect antibodies against viruses in a patient•Use antibodies to identify viruses in neutralization tests, viral hemagglutination, and Western blot•Nucleic acids•RFLPs (DNA fingerprint)•PCR (selectively amplifying and detecting key sequences)Virus IdentificationViruses: Morphology and Bacteriophage Life CycleFigure 13.1What is a Virus and How is it Built?•Obligate intracellular parasites•Morphology of a Virion•Size (1/1000 to 1/4 size of bacterium)•Composition•RNA vs DNA•Capsid, envelope, spikes •Shapes•helical, polyhedral, complex•Host ranges and grouping of viruses•Bacterial, plant, animal viruses•Propagation and study of viruses•Bacteriophage plaques on a lawn•Animal virus propagation•Identifying virusesBacterial Virus Life Cycles (DNA viruses)•Lytic Cycle (e.g. T4 bacteriophage)•Attachment•Penetration/Entry•Biosynthesis•Assembly•Lysis/ReleaseViruses cannot reproduce outside of a cell. They are extremely small and come in three different shapes. They are very specific for their hosts. In the lytic cycle of bacteriophages, they enter, reproduce, and leave.Figure 13.10.1Attachment:Phage attaches to host cell.Penetration:Phage pnetrates host cell and injects its DNA.Biosynthesis: Transcription/Translation andViral chromosome replication123Bacterial cell wallBacterial chromosomeCapsidDNACapsidSheathTail fiberBase platePinCell wallTailPlasma membraneSheath contractedTail coreLytic Lifecycle of a Bacteriophage IFigure 13.10.24Maturation/Assembly:Viral components are assembled into virions.Tail5Release:Host cell lyses and new virions are released.DNACapsidTail fibersLytic Lifecycle of a Bacteriophage IILytic Life Cycle OverallThe Lytic and Lysogenic CyclesFigure 13.12Viruses: Morphology and Bacteriophage Life CycleFigure 13.1What is a Virus and How is it Built?•Obligate intracellular parasites•Morphology of a Virion•Size (1/1000 to 1/4 size of bacterium)•Composition•RNA vs DNA•Capsid, envelope, spikes •Shapes•helical, polyhedral, complex•Host ranges and grouping of viruses•Bacterial, plant, animal viruses•Propagation and study of viruses•Bacteriophage plaques on a lawn•Animal virus propagation•Identifying virusesBacterial Virus Life Cycles (DNA viruses)•Lytic Cycle (e.g. T4 bacteriophage)•Attachment•Penetration/Entry•Biosynthesis•Assembly•Lysis/Release•Lysogenic Life CycleViruses cannot reproduce outside of a cell. They are extremely small and come in three different shapes. They are very specific for their hosts. In the lytic cycle of bacteriophages, they enter, reproduce, and