北京大学：《微生物学》课程PPT教学课件（英文版）Chapter 6 Viruses

Chapter 6 Viruses Virus: a noncellular genetic element that enlists a cell for its own replication, it has an extracellular state a virus particle containing nucleic acid surrounded by protein and other macromolecular components is called virion Viruses have a heavy dependence on host-cell structural and metabolic components Viruses can confer important new properties on their host cell

Chapter 6 Viruses Virus : a noncellular genetic element that enlists a cell for its own replication, it has an extracellular state. A virus particle containing nucleic acid surrounded by protein and other macromolecular components is called virion. Viruses have a heavy dependence on host-cell structural and metabolic components. Viruses can confer important new properties on their host cell

Classification of viruses Viruses can have either DNA or RNA as genetic material According to hosts viruses infect Bacterial viruses( Bacteriophage or噬菌体) Animal viruses(well studied) Plant viruses (less studied) According to nucleic acid structures DNA viruses(ss dna, ds dna) RNA viruses(ss rna, ds rna) RNA DNA VIruses(ss rna, ds dna)

Classification of Viruses Viruses can have either DNA or RNA as genetic material According to hosts viruses infect: – Bacterial viruses (Bacteriophage or 噬菌体） – Animal viruses (well studied) – Plant viruses (less studied) According to nucleic acid structures: – DNA viruses (ss DNA, ds DNA) – RNA viruses (ss RNA, ds RNA) – RNA DNA viruses (ss RNA, ds DNA)

Nature of the virion Virus size: 20 nm to 300 nm argest virus: Smallpox(天花病毒)is200nm Smallest virus;: Polio virus(脊髓灰质炎病毒)is28nm Virus genome: Smaller than those of cells, the largest known viral genome: vaccinIa(牛痘) is only 190 KB Bacterial genomes: 1000-9000 KB

Nature of the virion Virus Size: 20 nm to 300 nm Largest virus: Smallpox (天花病毒) is 200 nm Smallest virus: Polio virus (脊髄灰质炎病毒) is 28 nm Virus genome: Smaller than those of cells, the largest known viral genome: vaccinia (牛痘) is only 190 KB. Bacterial genomes: 1000-9000 KB

Virus structure Nucleo Envelope apsIa Capsomeres Capsid Nucleic Nucleic acid Capsid (composed of capso meres) Naked virus Enveloped virus Viruses consist of nucleic acids, capsid, and/or envelope

Virus Structure Viruses consist of nucleic acids, capsid, and/or envelope

Virus Symmetry Helical symmetry: Tobacco mosaic virus(TMv) Icosahedron: The most efficient arrangement for subunits in a closed shell Enveloped viruses: envelope consists of lipid bilayer with glycoproteins embedded in it. Its symmetry refers to its nucleocapside. Complex viruses: T4 bacteriophage

Virus Symmetry Helical symmetry: Tobacco mosaic virus (TMV). Icosahedron: The most efficient arrangement for subunits in a closed shell. Enveloped viruses: envelope consists of lipid bilayer with glycoproteins embedded in it. Its symmetry refers to its nucleocapside. Complex viruses: T4 bacteriophage

Virus Morphology 新

Virus Morphology

Enzymes in viruses Some viruses contain their own enzymes for their own purposes, such as Reverse transcriptase in retroviruses Neuraminadase: break down glycoprotein aiding liberation of the virus Lysozyme: bacteriophage

Enzymes in viruses Some viruses contain their own enzymes for their own purposes, such as – Reverse transcriptase in retroviruses – Neuraminadase: break down glycoprotein, aiding liberation of the virus – Lysozyme: bacteriophage

Cultivating Viruses Bacteriophage: bacterial Cultures Animal viruses: Tissue or cell cultures

Cultivating Viruses Bacteriophage: bacterial Cultures Animal viruses: Tissue or cell cultures

Quantification of viruses Plaque assay technique for quantification of awn of host cel bacterial viruses

Quantification of viruses Plaque assay technique for quantification of bacterial viruses

Quantification of animal viruses Tumor viruses may bot destroy cells but cause cells to grow faster than uninfected cells Confluent monolayer of tissue culture ceds a phenomenon calle transformation Transformed cells can be recognized as a small focus of growth

Quantification of animal viruses Tumor viruses may bot destroy cells but cause cells to grow faster than uninfected cells, a phenomenon called transformation. Transformed cells can be recognized as a small focus of growth