1. The Genetics of Viruses and Bacteria Microbial Models

2. Viruses come in many shapes and sizes

3. Compare the size of a Eukaoryotic cell, Bacterial Cell and a Virus

5. Herpes Virus

6. Measles

7. Polio

8. Ebola Virus

9. Discovery of the Virus  Adolph Meyer a German Scientist studied the Tobacco Mosaic Virus.  Thought it was caused by a very small bacteria because it could not be viewed through the microscope.

10. Tobacco Mosaic Virus

12. Dimitri Ivanosky a Russian Scientist  Filtered the sap to get rid of the bacteria.  The plants still received the infection when sprayed with the filtered sap.  Still thought the pathogen were very small bacteria.

13. Martinus Beijerink a Dutch Botanist  Discovered that this infectious particle could reproduce.  Sprayed plants with filtered sap and their sap infected other plants.  Infection was not diluted on subsequent infections.  Could not grow outside the host in culture medium.  Could not be inactivated with alcohol like bacteria

14. Wendell Stanley an American Scientist  Finally crystallized this infectious particle and viewed it under the electron microscope.

15. Viral Composition  Capsid – protein coat  Sometimes an envelope – glycoproteins  Nucleic acid – DNA or RNA. Never both. Can be single or double stranded.  Some have tail fibers – Bacteriophage T4

16. Viruses Are Obligate Intracellular Parasites  They lack their own enzymes to perform metabolism and reproduction.  They utilize the host’s enzymatic machinery to accomplish these tasks.  Viruses have a host range or are host specific. Rabies infects more than one host Rabies infects more than one host Eukaryotic viruses are usually tissue specific. Eukaryotic viruses are usually tissue specific. Rhinoviruses, Adenoviruses, Herpes, HIVRhinoviruses, Adenoviruses, Herpes, HIV

18. Reproductive Cycles of Virus  Lytic Cycle – destroys the host cell  Viral proteins are translated by host enzymes and new viral particles are produced.  Viral particles are assembled and the host cell is lysed. Host cell death occurs.  Bacterial cells possess restriction endonucleases that destroy foreign DNA.  The bacterial DNA is methylated to protect from destruction.

19. Lytic Cycle

20. Lysogenic Cycle Can Be Used For Cloning  Viruses can infect without destroying the host cell.  They integrate their DNA into the host cell and turn off their own genes.  These types of viruses are called temperate viruses.  Bacterial cells that possess these viral genes are celled prophages.  Viral DNA can be replicated along with the host cell’s DNA.

21. Lysogenic Cycle

22. Transduction

23. Lysogenic Viruses can be Triggered to Become Lytic Viruses  Radiation, chemicals or any host cell stress can cause the virus to enter the lytic cycle and destroy the host cell.  Some prophages express prophage genes that alter the phenotype of the host cell. Bacteria produce endotoxins that originate from viral genes.(Diptheria, Scarlet Fever and Botulism) Bacteria produce endotoxins that originate from viral genes.(Diptheria, Scarlet Fever and Botulism) Genes can be inserted into bacterial cells using viruses in a process called Transduction. Genes can be inserted into bacterial cells using viruses in a process called Transduction.

24. Transduction

25. HIV Infection

26. HIV Life Cycle

27. RNA as Viral Genetic Material  Messenger RNA serves as the template for new genetic material.  Reverse transcriptase produces DNA from mRNA.  Newly made DNA integrates into the host chromosome.  Unlike prophages, proviruses never leave.  The virus now is referred to as a provirus.  Viruses that do this are called retroviruses.

28. HIV Infection

29.  The host’s RNA polymerase transcribes viral RNA from the DNA. RNA serves as both a template and mRNA. mRNA. RNA viruses mutate more rapidly because replication of RNA does not have to undergo the same proofreading steps as replicating DNA.

30. Viroids  Viroids are tiny molecules of naked circular RNA that infect plants. - only several hundred nucleotides long. - a molecule can be an infectious agent. - disrupt metabolism by interferring with the host genome.

31. Prions Prions are infectious proteins. - cause degenerative brain diseases like scrapes and Creutzfeldt-Jakob disease. - abnormal shaped brain proteins induce normal proteins to assume an abnormal shape propagating itself. - abnormal shaped brain proteins induce normal proteins to assume an abnormal shape propagating itself.

32. Prions