1. Viruses Biology: Kingdoms Research Project Mr. Jones EM of Enveloped Virus with receptor molecules

2. Viruses: Overview & Concepts Structure Adaptations Reproduction & Development Diversity Phylogeny Importance TEM: Ebola Virus

3. Definition: Virus Sub microscopic entity consisting of a single nucleic acid (N.A) surrounded by a protein coat, or capsid, capable of replication only within a living host. Obligate Intracellular Parasite

4. Are Viruses Alive? Characteristics of life What Viruses Don’t... –Respire (produce energy) –Metabolize (make biological molecules) –Grow & Develop What Viruses Do... –Reproduce- obligate to a host –Adapt/Evolve- change through time

5. Viral Morphology (Structure) Basic Structure: 2 principle structures –Protein Capsid Outer covering protecting core & giving shape –Inner Nucleic Acid Core (RNA or DNA) Used in viral classification –*Envelope or Lipoprotein Coat Enveloped viruses- similar to their eukaryotic host cell’s plasma membrane Not present in all viruses

6. Basic Enveloped Viral Structure Influenza Virus following lytic cycle

7. Structure: Capsid Protein Arrangement Protein Arrangement Determines: –1. Viral shape- images on next slide Polyhedral (HPV, Polio, Adenovirus) Helical (Tabacco Mosiac Virus) Enveloped (Influenza, HIV) Binal (baceriophages) –2. What host a virus can infect –3. Method virus will infect host

8. Typical Viral Shapes

9. Viral Size Extremely Small... –most range 5nm-300nm –as small as ribosomes –between 4-900 genes Yet Complex... –Icosahedrals like polio & adenoviruses can have up to 20 symmetrical sides Learn more in the Class Project DYK?- 1 drop of blood can contain as many as 6 billion viruses! Bacteriophages infect bacteria

10. Virus Classification Classified by Shape & Nucleic Acid Class DNA viruses – stable, do not mutate as rapidly –Single-stranded or double-stranded –Smallpox, Hepatitis B RNA viruses – mutate rapidly, unstable –Single-stranded or double-stranded –HIV, Rhinovirus (common cold)

11. Viral Classification Chart

12. Naming Viruses Once named by... –Common names such as... Diseased they cause (rabies, poliovirus) Organ or tissue they infect (adenovirus: from adenoid tissue where common cold is found) Universal System(s) –Families with Genus name + “virus” & species name + “viridae” (herpesviridae)

13. Viral Adaptations Viruses evolve quickly Have several methods of infecting a host Viruses can survive for long periods of time both inside & outside of a host Recognition & Attachment –Virus receptor molecule to cell receptor site –Viral species are specific to host Smallpox- affects only humans Polio- affects only certain human nerve cells Bacteriophases invading E.coli

14. Viral Adaptations Transmission –Air, fluids (blood, fecal, sexual), animal vectors (insects, mice, monkeys) Methods of entering & leaving host –Direct attachment to receptor molecule (Polyhedral viruses) –Endocytosis with cell membrane (Enveloped viruses) –Attachment by tail fibers (Binal viruses)

15. Viral Reproduction Reproductive Overview: A Virus... –infects a host through a reception mechanism –alters host ribosomes, DNA, or RNA –uses host metabolism to replicate N.A. Host cell makes & assemble new viruses Host cell lyses (burst) leading to cell death –All host cell’s eventually enter a Lytic Cycle

16. Viral Reproduction Diagram

17. Viral Diversity There are 22 classes of bacteria. 400 identified plant viruses causing up to 1,000 identified diseases Eastimated: –1000’s of animal viruses causing as many as 10,000 diseases –10 31 bacteriophages on Earth alone

18. Viral Diversity Reproductive Cycles –Lytic & Lysogenic Cycles Provirus –viral DNA integrated into host DNA –remains dormant or inactive Retroviruses –contain enzyme reverse transcriptase RNA is transcribed into DNA (ex. HIV)

19. Lytic Cycle Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell. The viral nucleic acid takes over protein synthesis, creating new viruses. The host cell lyses releasing the newly formed viruses. Cycle repeats exponentially

20. Cell lyses Before attachment Attachment/Reception Penetration of N.A. Replication of viral proteins Viral assembly

21. Lysogenic Cycle Viral N.A. are integrated into host’s DNA becoming a provirus Provirus is replicated with host cell replication (mitosis) Infect cell’s turn lytic, killing host cells Lysogenic Cycle Video –http://www.youtube.com/watch?v=_J9- xKitsd0

22. Lysogenic Cycle

23. Adaptations- Comparing Cycles Lytic –Kills host cells –Mutates quickly & ramdomly Often without benefit to the virus –Rapid Typical lytic cycle- 30 minutes to produce 200 viruses Lysogenic, Provirus, & Retrovirus –Uses cell’s reproduction & lysis –NA integration into cell DNA –remain dormant for periods of time –Slower High transmission rate Slower but more effective mutation

24. Viral Phylogeny Viruses likely evolved from the host themselves Some may have evolved in protists such as amoebas HIV phylogeny & evolution –Emergent Viruses- host to human

25. HIV Phylogeny- SIV to HIV

26. Importance Viruses drive evolution –Adapted organisms survive –Controls populations –Mutate genetics of host Both for the good & bad Gene Therapy & Viral Vectors –Using viruses to transmit healthy genes to people with genetic disorders & diseases

27. Importance No Cure- most drugs affect enzymes, cell membranes, or reproductive cycle; virus have almost none of these traits Vaccines & immunization –Cowpox & Smallpox (eradicated) HIV can infect 10 billion cells per day, the body can only replace 1.8 AIDS Prevalence –http://www.avert.org/worldstats.htmhttp://www.avert.org/worldstats.htm –http://kwanzaakeepers.com/africa-aids-death- count/africa-aids-death-count.htmhttp://kwanzaakeepers.com/africa-aids-death- count/africa-aids-death-count.htm One sub-Saharan African is infected with HIV every 9 seconds. One person dies from AIDS every 13 seconds.