Viruses

1. Viruses Latin: Poison – slippery toxin

2. What are Viruses? • Smaller and simpler than bacteria • NOT made up of cells • Lack most metabolic machinery, so must hijacka cell to reproduce • Are little more than a combination of nucleic acid and protein –“genes” in a protein coat • *Viruses are NOT considered ‘living things’

3. Viral Structure 2 parts: • Capsid– protein “coat” • Nucleic Acid---DNA or RNA

4. ClassificationViral Genomes = Classification • 4 Types • 1. Double Strand DNA • 2. Single Strand DNA • 3. Double Strand RNA • 4. Single Strand RNA • Classified “DNA-like or RNA-like/Retrovirus” • Further naming is based on surface proteins • H1N1 – H proteins = hemoggluttin, N = neuraminidase

5. Common Viruses • Flu Virus • HIV: Retrovirus • Herpes Simplex I • Chicken pox virus (shingles) • West Nile Virus: most people infected never know they have it! • Fifths Disease • Cold Virus Flu Virus

6. Viral Reproduction (Infection) • Virus uses host’s machinery to replicate viral genome • Host’s machinery used to make capsid proteins • Use transcription and translation. • New viral genomes and capsids are assembled into new viruses

7. Lytic vs. Lysogenic Cycles • Lytic cycle -virus takes over the host cell immediately and reproduces quickly • Virulent infections – quick! • Infections you “get over” • Ex. Cold virus, influenza • Lysogenic cycle - virus “hides” in host’s DNA until optimal conditions for viral survival are present • Lifetime Infections • Ex. HIV, herpes

8. Lytic Cycle Lytic Cycle Virus infect and use host’s machinery to replicate many genomes and proteins “Lyses” host cell quickly after replication and assembly of new viruses

9. Lytic Virus Lytic Bacteriophage

10. Lysogenic Cycle Instead of Lysing the cell quickly, virus “hides out” in host Replicates and divides with host cells creating many new viruses Conditions right, virus enters Lytic Cycle, breaking the host cell, leaving to infect more

11. Lysogenic Virus Prophage infection

12. Ex: Lysogenic CycleHerpes Virus in Humans • Herpesviruses – genomes of double-stranded DNA • Reproduce within the cell nucleus • Hides in cell DNA – replicated during mitosis • Infections tend to recur throughout life in times of stress  viruses will emerge from thousands of cells then

13. RNA Viruses and Retroviruses • These viruses have a HIGH MUTATION RATE • There is no good PROOFREADING mechanism like there is when going from DNA to RNA • These means there are many different STRAINS of RNA viruses and Retroviruses • Makes VACCINES very difficult to develop • Example: HIV

14. But what about Bird Flu?? • Host range is specific – lock & key • Sometimes virus can mutate & be able to “change hosts” • Zoonotic Virus – from different animal host • Usually severe – immunity? • Ex: Ebola, Hendra, Swine Flu

15. Why not antibiotics? • Antibiotics only target bacteria • Nyquil? Robitussin? Tylenol Cold? • Immune System • Destroys viruses physically or rids body of them – antibodies • Antiviral medicines • Prevent HOST cells from life processes • DNA replication or Protein Synthesis • Ex: Abreva, AZT

16. Vaccines: the war against the virus • Prevention • Injecting WEAKENED or “HEAT KILLED” virus particles to cause your immune system to recognize the virus quickly • Create antibodies (Memory cells – B & T cells) • When in contact with the real virus, your IMMUNE SYSTEM should recognize the virus and come to the rescue

17. The Amazing World of Bacteria

18. Differences Between Bacteria and Viruses Virus • Non-Living • Cannot perform metabolic functions • Some - no DNA • Cannot move • Cannot reproduce without a host • Not classified Bacteria • Living • Prokaryotes • DNA • Metabolic functions: replication, protein synthesis, use and obtain own energy • Move • Reproduce • Classified

19. Differences between Prokaryotes and Eukaryotes • Prokaryotes • No nucleus or membrane-bound organelles • Unicellular only • Eukaryotes are not AS affected by most antibiotics • difference in cell wall • metabolism • Prokaryotes - extreme environments • most eukaryotes can’t tolerate • Fun Fact – there are more prokaryotes in a hand full of dirt (or cup full of sea water) than humans that have ever lived!!!

20. 2 Kingdoms of Bacteria • Eubacteria – • Peptidoglycan in cell wall • Affected by antibiotics • Archaebacteria – “Ancient Bacteria”; • Extreme Environments • No peptidoglycan in cell wall • Not affected by antibiotics We will focus on Bacteria (Eubacteria)

21. Typical Prokaryotic Structure

22. Movement • Flagella – help propel the cell • On outside of cell wall • Scattered all over surface or concentrated at the ends • Cilia – hair-like projections outside cell • Slime– oozes from cell • helps bacteria glide along

23. Cell Wall • 2 different types in Eubacteria • Peptidoglycan on outside layer • Lipid carbohydrate layer over peptidoglycan layer • Antibiotics target mainly peptidoglycan in cell wall • To determine cell wall structure, use Gram Stain: • Gram (+) means peptidoglycan in outer wall - purple • Gram (-) means outer layer of lipid/carb covers peptidoglycan layer- pink/red Antibiotics mainly kill Gram (+) bacteria

24. Mix of Gram(+) and (-) Bacteria

25. Endospore – Bacterial Protection Phase • If growth conditions are not suitable for bacteria: • It grows a thick wall of keratin protein around cell wall • Protects • Can remain dormantindefinitely • Can grow once conditions return to favorable • Why we must autoclave

26. Naming bacteria – shape and colony type • Unicellular • True colonies – *chains (strepto) *clusters (staphalo) • Differ in shape – 3 most common *spherical (coccus or cocci) *rod-like (bacillus or bacilli) *helical (spirillum or spirilla, spirochetes) • Diameter ranges between 1-5 um; largest is .75 mm in diameter

27. Label these shapes

28. Modes of Nutrition: Very Diverse • Nutrition of prokaryotes – how organim obtains energy 4 categories: • photoautotrophs – use light to make food • chemoautotrophs – need CO2 as carbon source, and get chemical energy from inorganic substances • photoheterotrophs – use light to make energy, but need a carbon source to start with • chemoheterotrophs– must “eat” other organisms to get food in chemical form Most bacteria are this type • Saprobes – decomposing bacteria • Parasites – infectious bacteria

29. Reproduction • Binary Fission: Asexual Reproduction • No recombination of genetic material! • Bacterial cell just splits in half and have two cells from the original • Conjugation : Sexual Reproduction • bacteria can swap plasmids (2nd genome)

30. Prokaryotes are not all bad… • Many do cause disease (pathogenic), but others are symbiotic (E. coli in intestines), help with cycling nutrients (decomposers and carbon cycle) • Many are important in food processing (yogurt, cheese, etc) • Are about 5,000 species known, could be as many as 4 million

31. Preventing bacterial infection • Sterilization of surfaces (with antiseptics, heat, or steam) • Cooling, freezing food • Dehydrating food (salt curing) • Use chemical preservatives • Radiation • Pasteurization (heating liquids) • Canning • Washing hands!!! *Antibiotics are used only AFTER have infection present

32. Antibiotics vs. Antibodies vs. Antiseptics • Antibodies – produced by white blood cells in the body (internal line of defense) - can use vaccines • Antibiotics – kill bacteria using chemicals that are specific to bacteria metabolism and structure *introduced IN TO body or *ON TO site of infection as surface medication • Antiseptics - Kill bacteria on OUTSIDE of body or on membranes that line areas leading to inside (ex. Mouth) • Disinfectants – destroy bacteria/viruses on non-living surfaces • Lysol wipes, clorox,