华中农业大学：《食品微生物学》课程PPT教学课件（Food Microorganism）Chapter 5 Viruses

Chapter 5 Viruses

Chapter 5 Viruses

5.1 General Properties of Viruses 5.2 General Features of Virus Reproduction 5.3 Overview of Bacterial Viruses 5.4 Temperate Bacteriophages: Lysogeny and Lambda 5.5 Overview of Animal Viruses 5.6 Pox Viruses 5.7 Adcnoviruses 5.8 Retroviruses 5.9 Viroids and Prions Chapter outline

5.1 General Properties of Viruses 5.2 General Features of Virus Reproduction 5.3 Overview of Bacterial Viruses 5.4 Temperate Bacteriophages: Lysogeny and Lambda 5.5 Overview of Animal Viruses 5.6 Pox Viruses 5.7 Adcnoviruses 5.8 Retroviruses 5.9 Viroids and Prions Chapter outline

(1) their simple, acellular organization (2) the absence of both DNA and RNA in the same virion, (3) their inability to reproduce independently of cells and carry out cell division as prokaryotes and eukaryotes do. viruses differ from living cells in at least three ways: 5.1 General Properties of Viruses

(1) their simple, acellular organization (2) the absence of both DNA and RNA in the same virion, (3) their inability to reproduce independently of cells and carry out cell division as prokaryotes and eukaryotes do. viruses differ from living cells in at least three ways: 5.1 General Properties of Viruses

Virion, the extracellular phase, posses few if any enzymes and can not reproduce independently of living cells. In the intracellular phase, viruses exist primarily as replicating nucleic acids that induce host metabolism to synthesize virion components; eventually complete virus particles or virions are released. extracellular and intracellular Viruses can exist in two phases

Virion, the extracellular phase, posses few if any enzymes and can not reproduce independently of living cells. In the intracellular phase, viruses exist primarily as replicating nucleic acids that induce host metabolism to synthesize virion components; eventually complete virus particles or virions are released. extracellular and intracellular Viruses can exist in two phases

Hosts and size Three main classes - animal viruses, bacterial viruses (bacteriophages), and plant viruses. The particular host range of a virus is determined by the virus's requirements for its specific attachment to the host cell and the availability within the potential host of cellular factors required for viral multiplication

Hosts and size Three main classes - animal viruses, bacterial viruses (bacteriophages), and plant viruses. The particular host range of a virus is determined by the virus's requirements for its specific attachment to the host cell and the availability within the potential host of cellular factors required for viral multiplication

Virus particles (virions) vary widely in size and shape. Viruses are smaller than cells, ranging in size from 0.02 to 0.3 μm. A common unit of measure for viruses is the nanometer, which is 1000 times smaller than 1 um and 1 million times smaller than 1 mm. Smallpox virus, one of the largest viruses, is about 200 nm in diameter (a bit smaller than the size of the smallest bacteria); poliovirus, one of the smallest, is only 28 nm in diameter (about the size of a ribosome)

Virus particles (virions) vary widely in size and shape. Viruses are smaller than cells, ranging in size from 0.02 to 0.3 μm. A common unit of measure for viruses is the nanometer, which is 1000 times smaller than 1 um and 1 million times smaller than 1 mm. Smallpox virus, one of the largest viruses, is about 200 nm in diameter (a bit smaller than the size of the smallest bacteria); poliovirus, one of the smallest, is only 28 nm in diameter (about the size of a ribosome)

Viruses vary considerably in size. Although most are quite a bit smaller than bacteria, some of the larger viruses (such as the smallpox virus) are about the same size as some very small bacteria (such as the mycoplasmas, rickettsias, and chlamydias). Size Viruses range from 20 to 300 nm in diameter

Viruses vary considerably in size. Although most are quite a bit smaller than bacteria, some of the larger viruses (such as the smallpox virus) are about the same size as some very small bacteria (such as the mycoplasmas, rickettsias, and chlamydias). Size Viruses range from 20 to 300 nm in diameter

Genome in virion Viral genomes. The genomes of viruses can be composed of either DNA or RNA, and some use both as their genomic material at different stages in their life cycle. However , only one type of nucleic acid is found in the virion of any particular type of virus. This can be single￾stranded (ss), double-stranded (ds), or in the case of the hepadnaviruses, partially double-stranded

Genome in virion Viral genomes. The genomes of viruses can be composed of either DNA or RNA, and some use both as their genomic material at different stages in their life cycle. However , only one type of nucleic acid is found in the virion of any particular type of virus. This can be single￾stranded (ss), double-stranded (ds), or in the case of the hepadnaviruses, partially double-stranded

The comparative sizes of several viruses and bacteria:

The comparative sizes of several viruses and bacteria:

• Most viruses are too small to be seen under light microscope. • All viruses consists of an RNA or DNA core genome surrounded by a protein coat capsid. • The combined viral genome and capsid is called the nucleocapsid. Structure of viruses

• Most viruses are too small to be seen under light microscope. • All viruses consists of an RNA or DNA core genome surrounded by a protein coat capsid. • The combined viral genome and capsid is called the nucleocapsid. Structure of viruses