1. Copyright © 2010 Pearson Education, Inc. General Characteristics of Viruses Differentiate a virus from a bacterium.  Obligatory intracellular parasites  Contain DNA or RNA simultaneously in the virion  Contain a protein coat (capsid)  Some are enclosed by an envelope  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 1

2. Copyright © 2010 Pearson Education, Inc. Virion Structure Figure 13.2a  Nucleic acid  DNA or RNA  Capsid  Capsomeres  Envelope  Spikes 2

3. Copyright © 2010 Pearson Education, Inc. Figure 13.3 Morphology of an Enveloped Virus 3

4. Copyright © 2010 Pearson Education, Inc. Figure 13.16b Enveloped Viruses 4

5. Copyright © 2010 Pearson Education, Inc. Figure 13.4 Morphology of a Helical Virus 5

6. Copyright © 2010 Pearson Education, Inc. Figure 13.5 Morphology of a Complex Virus 6

7. Copyright © 2010 Pearson Education, Inc. Figure 13.6 Growing Viruses  Viruses must be grown in living cells  Bacteriophages form plaques on a lawn of bacteria 7

8. Copyright © 2010 Pearson Education, Inc. Figure 13.7 Growing Viruses  Animal viruses may be grown in living animals or in embryonated eggs 8

9. Copyright © 2010 Pearson Education, Inc. Virus Identification  Cytopathic effects: Detectable c hanges in the host cell due to viral infection (p. 441)  Blood serum (serology) tests  Detect antibodies against viruses in a patient  Use antibodies to identify viruses in neutralization tests, viral hemagglutination, and Western blot  Nucleic acids: Studies of the DNA/RNA 9

10. Copyright © 2010 Pearson Education, Inc. Figure 13.9 Virus Identification: Cytopathic Effect 10

11. Copyright © 2010 Pearson Education, Inc. Lytic Cycle of a T-Even Bacteriophage 1 2 3 Figure 13.11 11

12. Copyright © 2010 Pearson Education, Inc. 4 Figure 13.11 Lytic Cycle of a T-Even Bacteriophage 12

13. Copyright © 2010 Pearson Education, Inc. Figure 13.12 The Lysogenic Cycle 13

14. Copyright © 2010 Pearson Education, Inc. Figure 13.14a Attachment, Entry, Uncoating  By pinocytosis 14

15. Copyright © 2010 Pearson Education, Inc. Figure 13.14b Attachment, Entry, Uncoating  By fusion 15

16. Copyright © 2010 Pearson Education, Inc. Figure 13.15 Multiplication of DNA Virus 16

17. Copyright © 2010 Pearson Education, Inc. Figure 13.17a Sense Strand (+ Strand) RNA Virus 17

18. Copyright © 2010 Pearson Education, Inc. Figure 13.17b Antisense Strand (– Strand) RNA Virus 18

19. Copyright © 2010 Pearson Education, Inc. Figure 13.17c Double-Stranded RNA Virus 19

20. Copyright © 2010 Pearson Education, Inc. Figure 13.19 Multiplication of a Retrovirus 20

21. Copyright © 2010 Pearson Education, Inc. Figure 13.20 Release of an enveloped virus through ‘budding’ 21

22. Copyright © 2010 Pearson Education, Inc. 22

23. Copyright © 2010 Pearson Education, Inc. 23