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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation prepared by Christine L. Case Microbiology.

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Presentation on theme: "Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation prepared by Christine L. Case Microbiology."— Presentation transcript:

1 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation prepared by Christine L. Case Microbiology B.E Pruitt & Jane J. Stein AN INTRODUCTION EIGHTH EDITION TORTORA FUNKE CASE Chapter 13 Viruses, Viroids, and Prions

2 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Differentiate between a virus and a bacterium. Viruses may be regarded as exceptionally complex aggregations of nonliving chemicals OR exceptionally simple living microbes.

3 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Viruses Viruses contain DNA or RNA And a protein coat Some are enclosed by an envelope (lipids, proteins, and carbohydrates) Some viruses have spikes Most viruses infect only specific types of cells in one host Host range is determined by specific host attachment sites and cellular factors Obligatory intracellular parasites, causing synthesis of specialized elements that transfer viral nucleic acid to other cells.

4 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Viruses (range from 20 to 1000 nm) Figure 13.1 nm = m

5 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Nonenveloped Polyhedral Viruses Figure 13.2a, b Describe the chemical composition and physical structure of an enveloped and a nonenveloped virus. Virion = complete, fully developed viral particle of nucleic acid surrounded by a coat

6 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Enveloped Helical Virus Viruses contain either DNA or RNA, but never both. Nucleic acid may be single or double stranded, linear or circular, or divided into several separate molecules.

7 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Helical Viruses Figure 13.4a, b Helical viruses look like long or coiled threads. Their capsids are hollow cylinders surrounding the DNA/RNA.

8 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Complex Viruses Figure 13.5a Capsid – protein coat surrounding nucleic acid Composed of capsomeres, single or multiple proteins

9 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Viral Taxonomy Classification based on type of nucleic acid, replication, and morphology. 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 Define viral species.

10 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Viral Taxonomy Herpesviridae Herpesvirus Human herpes virus 1, HHV 2, HHV 3 Retroviridae Lentivirus Human Immunodeficiency Virus 1, HIV 2 Give an example of a family, genus, and common name for a virus.

11 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

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15 Growing Viruses Viruses must be grown in living cells. Bacteriophages form plaques (clearings) on a lawn of bacteria. Easiest to grow Figure 13.6 Describe how bacteriophages are cultured.

16 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Growing Viruses Viruses must be grown in living host cells. Animal viruses may be grown in living animals or in embryonated eggs. Figure 13.7 Describe how animal viruses are cultured.

17 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Growing Viruses Animal and plants viruses may be grown in cell culture. Continuous cell lines may be maintained indefinitely. Cytopathic effects due to viral growth Figure 13.8

18 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cytopathic effect of viruses Figure 13.9 Uninfected mouse cells form monolayer (left). Infected cells 24 hours later pile up and round up (right).

19 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 – restriction fragment length polymorphisms PCR – polymerase chain reaction (used to identify West Nile virus in U.S. in 1999) Virus Identification List three techniques that are used to identify viruses.

20 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings AttachmentPhage attaches by tail fibers to host cell PenetrationPhage lysozyme opens cell wall, tail sheath contracts to force tail core and DNA into cell BiosynthesisProduction of phage DNA and proteins MaturationAssembly of phage particles ReleasePhage lysozyme breaks cell wall Multiplication of Bacteriophages (Lytic Cycle)

21 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Attachment: Phage attaches to host cell. Penetration: Phage penetrates host cell and injects its DNA. Merozoites released into bloodstream from liver may infect new red blood cells Bacterial cell wall Bacterial chromosome Capsid DNA Capsid Sheath Tail fiber Base plate Pin Cell wall Tail Plasma membrane Sheath contracted Tail core Lytic cycle of T-even bacteriophage Describe the lytic cycle of T-even bacteriophages.

22 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Maturation: Viral components are assembled into virions. Tail 5 Release: Host cell lyses and new virions are released. DNA Capsid Tail fibers Lytic cycle of T-even bacteriophage Burst time is generally about 20 – 40 minutes after phage absorption. Burst size ranges from 50 to 200 new phage cells.

23 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings One-step Growth Curve for bacteriophage Figure During biosynthesis and maturation, separate components of DNA and protein may be detected in the host cell.

24 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Lytic cyclePhage causes lysis and death of host cell Lysogenic cycleProphage DNA incorporated in host DNA

25 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The Lysogenic Cycle – bacteriophage lambda in E.coli Figure Describe the lysogenic cycle of bacteriophage lambda.

26 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Specialized Transduction Figure Prophage exists in galactose-using host (containing the gal gene). Phage genome excises, carrying with it the adjacent gal gene from the host. Phage matures and cell lyses, releasing phage carrying gal gene Prophage gal gene Bacterial DNA Galactose-positive donor cell gal gene Phage infects a cell that cannot utilize galactose (lacking gal gene). 4 Galactose-negative recipient cell Along with the prophage, the bacterial gal gene becomes integrated into the new host’s DNA. 5 Lysogenic cell can now metabolize galactose. 6 Galactose-positive recombinant cell

27 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

28 AttachmentViruses attaches to cell membrane PenetrationBy endocytosis or fusion UncoatingBy viral or host enzymes BiosynthesisProduction of nucleic acid and proteins MaturationNucleic acid and capsid proteins assemble ReleaseBy budding (enveloped viruses) or rupture Multiplication of Animal viruses

29 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Attachment, Penetration, and Uncoating Figure Entry of herpes simplex virus into an animal cell.

30 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Compare and contrast the multiplication cycle of DNA- and RNA-containing animal viruses.

31 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Multiplication of Papovarius, a DNA-containing Virus Figure Virion attaches to host cell Virion penetrates cell and its DNA is uncoated Early transcription and translation; enzymes are synthesized DNA Late transcription; DNA is replicated 4 Late translation; capsid proteins are synthesized 5 Virions mature 6 Capsid Papovavirus Host cell DNA Cytoplasm Virions are released 7 Capsid proteins mRNA

32 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings DNA-containing animal viruses: individual capsomeres visible

33 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings DNA-containing animal viruses: envelop around this herpes simplex virus broken (fried egg appearance)

34 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Pathways of Multiplication for RNA-Containing Viruses Figure 13.17

35 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings RNA-containing animal viruses: rubella (left), mouse mammary tumor virus (right).

36 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Multiplication & Inheritance in a Retrovirus Figure Retrovirus penetrates host cell. Virion penetrates cell and its DNA is uncoated The new viral DNA is transported into the host cell’s nucleus and integrated as a provirus. The provirus may divide indefinitely with the host cell DNA DNA Transcription of the provirus may also occur, producing RNA for new retrovirus genomes and RNA that codes for the retrovirus capsid and envelope proteins. 4 Mature retrovirus leaves host cell, acquiring an envelope as it buds out. 5 Capsid Reverse transcriptase Virus Two identical + stands of RNA DNA of one of the host cell’s chromosomes Provirus Host cell Reverse transcriptase Viral RNA RNA Viral proteins Identical strands of RNA

37 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Release of an enveloped virus by budding Figure Most enveloped viruses take part of host’s plasma membrane for their envelope.

38 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Activated oncogenes transform normal cells into cancerous cells. (malignant transformation) Transformed cells have increased growth, loss of contact inhibition, tumor specific transplant and T antigens, chromosome abnormalities, can produce tumors when injected into susceptible animals. Several DNA viruses and retroviruses are oncogenic. The genetic material of oncogenic viruses becomes integrated into the host cell's DNA. Cancer Define oncogene and transformed cell.

39 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Oncogenic DNA Viruses Adenoviridae Heresviridae Poxviridae Papovaviridae Hepadnaviridae Oncogenic Viruses Oncogenic RNA viruses Retroviridae Viral RNA is transcribed to DNA which can integrate into host DNA HTLV 1 HTLV 2 Discuss the relationship of DNA- and RNA-containing viruses to cancer. Retroviruses carry reverse transcriptase which allows RNA to DNA, permitting oncogenic properties

40 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Latent Viral Infections Virus remains in asymptomatic host cell for long periods Cold sores, shingles Persistent Viral Infections Disease processes occurs over a long period, generally fatal Subacute sclerosing panencephalitis (measles virus) Provide an example of a latent viral infection.

41 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Differentiate between persistant viral infections and latent viral infections. Persistent viral infections are caused by conventional viruses, occur over a long period, generally fatal.

42 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Infectious proteins first discovered in 1980’s Inherited and transmissible by ingestion, transplant, & surgical instruments Spongiform encephalopathies: Sheep scrapie, Creutzfeldt-Jakob disease, Gerstmann-Sträussler- Scheinker syndrome, fatal familial insomnia, mad cow disease PrP C, normal cellular prion protein, on cell surface PrP Sc, scrapie protein, accumulate in brain cells forming plaques Prions Discuss how a protein can be infectious.

43 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Prions Figure PrP c PrP Sc Endosome Lysosome How a protein can be infectious: if an abnormal prion protein enters cell, it changes a normal prion to PrP Sc, which changes another normal PrP (accumulation of abnormal PrP Sc )

44 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Some Plant Viruses Table 13.6 Name a virus that causes a plant disease.

45 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Plant Viruses Plant viruses enter through wounds or via insects Viroids Viroids are infectious RNA; potato spindle tuber disease Prion = infectious protein Linear and circular potato spindle tuber viroid Differentiate between virus, viroid, and prion.

46 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Virus Families Single-stranded DNA, nonenveloped viruses Parvoviridae Human parvovirus Fifth disease Anemia in immunocompromised patients

47 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Double-stranded DNA, nonenveloped viruses Mastadenovirus Respiratory infections in humans Tumors in animals

48 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Double-stranded DNA, nonenveloped viruses Papillomavirus (human wart virus) Polyomavirus Cause tumors, some cause cancer

49 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Double-stranded DNA, nonenveloped viruses Orthopoxvirus (vaccinia and smallpox viruses) Molluscipoxvirus Smallpox, molluscum contagiosum, cowpox

50 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Simplexvirus (HHV1 and HHV 2) Varicellavirus (HHV 3) Lymphocryptovirus (HHV 4) Cytomegalovirus (HHV 5) Roseolovirus (HHV 6) HHV 7 Kaposi's sarcoma (HHV 8) Some herpesviruses can remain latent in host cells Double-stranded DNA, nonenveloped viruses

51 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Double-stranded DNA, nonenveloped viruses Hepadnavirus (Hepatitis B virus) Use reverse transcriptase to produce DNA from mRNA

52 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Single-stranded RNA, + strand, nonenveloped Enterovirus Enteroviruses include poliovirus and coxsackievirus Rhinovirus Hepatitis A virus

53 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Single-stranded RNA, + strand, nonenveloped Hepatitis E virus Norovirus (Norwalk agent) causes gastroenteritis

54 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Single-stranded RNA, + strand, nonenveloped Alphavirus Alphaviruses are transmitted by arthropods; include EEE, WEE Rubivirus (rubella virus)

55 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Single-stranded RNA, + strand, nonenveloped Arboviruses can replicate in arthropods; include yellow fever, dengue, SLE, and West Nile viruses Hepatitis C virus

56 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Single-stranded RNA, + strand, nonenveloped Coronavirus Upper respiratory infections

57 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Single-stranded RNA, – strand, one RNA strand Vesiculovirus Lyssavirus (rabies virus) Cause numerous animal diseases

58 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Single-stranded RNA, – strand, one RNA strand Filovirus Enveloped, helical viruses Ebola and Marburg viruses

59 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Single-stranded RNA, – strand, one RNA strand Paramyxovirus Morbillivirus Paramyxovirus causes parainfluenza, mumps and Newcastle disease

60 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Single-stranded RNA, – strand, one RNA strand Hepatitis D virus Depends on coinfection with Hepadnavirus

61 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Influenzavirus (Influenza viruses A and B) Influenza C virus Envelope spikes can agglutinate RBCs Single-stranded RNA, – strand, multiple RNA strands

62 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Bunyavirus (CE virus) Hantavirus Single-stranded RNA, – strand, multiple RNA strands

63 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Arenavirus Helical capsids contain RNA- containing granules Lymphocytic choriomeningitis VEE and Lassa Fever Single-stranded RNA, – strand, multiple RNA strands

64 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Lentivirus (HIV) Oncogenic viruses Use reverse transcriptase to produce DNA from viral genome Includes all RNA tumor viruses Single-stranded RNA, two RNA strands, produce DNA

65 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Double-stranded RNA, nonenveloped Reovirus (Respiratory Enteric Orphan) Rotavirus Mild respiratory infections and gastroenteritis Colorado tick fever


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