Viruses and Bacteria

1. Viruses and Bacteria Chapter 18

2. Pathogen Anything that causes a disease.

3. What is a virus? • Considered non-living particles by most biologists because they: • Do not carry out cellular respiration • Do not grow and develop • Cannot replicate on their own • Viruses are named after: • The disease they cause (poliovirus) • The organ they infect (adenovirus)

4. Viral Structure 1. Genetic Material in the form of: • DNA • RNA • Capsid: -outer protein coat

5. Viruses • Herpes virus • Adenovirus • Polio virus

6. Bacteriophages • “phage” • Is a virus that attacks bacteria

7. Viruses are Specific • Each virus is specialized • Most viruses are species-specific • Many viruses are also cell-specific

8. Viral Replication Cycles • Lytic Cycle (Fast and Furious) • Kills the host cell • Examples: Flu and Cold • Lysogenic Cycle (Lingers) • Similar to lytic cycle but does not immediately kill host cell • Viral genetic material recombines with host cell’s DNA • Examples: HIV, Herpes, and Chicken pox

9. AIMAR Lytic Cycle Step 1: A virus attaches to a host cell. Step 2: Virus injects its genetic material into the host cell. Step 3: The enzymes make parts for more new viruses. Step 4: The new parts assemble into new viruses. Step 5: The new particles lyse (burst) from the host

11. Lysogenic Cycle

13. Vaccines They can't cause an infection, but the immune system still sees them as an enemy and produces antibodies in response. An antigen is like a name tag on a pathogen The next time your immune system encounters that pathogen/antigen it triggers a response to fight the infection.

14. Prokaryotes • Unicellular organisms without membrane-bound organelles • 2 Kingdoms • Archaebacteria • Eubacteria

15. Archaebacteria • Live in harsh environments • 3 types • Methane-producers • “Methanogens” • Marshes • Lake sediments • Animal digestive tracts • Salt-dwellers • “Halophiles” • Dead Sea • Heat/Acid-dwellers • “Thermoacidophiles” • Deep ocean vents

16. Eubacteria: The Heterotrophs • Bacteria that obtain their nutrients from elsewhere • Some are parasites • Feed off of living organisms • Some are saprophytes • Feed on dead organisms • Feed on organic wastes (recyclers)

17. Eubacteria: Photosynthetic Autotrophs • Bacteria that convert solar energy into food • Cyanobacteria or blue-green algae • Found in aquatic environments • Composed of chains of independent cells

18. Eubacteria: Chemosythetic Autotrophs • Break down and release energy from inorganic compounds such as H2S • Important in converting atmospheric nitrogen into usable forms plants need • Nitrogen Fixation

19. Structure

20. Identifying Bacteria: Gram Stain • Gram staining reflects differences in cell wall composition • Gram-positive bacteria stain blue/violet • Gram-negative bacteria stain pink

21. Identifying Bacteria: Shapes

22. Bacterial Reproduction • Asexually by binary fission • Very rapid at optimal conditions • can double every 20 minutes

23. Bacterial Reproduction • Sexually by conjugation

24. Common Bacterial Diseases

25. Beneficial Bacteria • Nitrogen Fixation N2→ NO2- + NO3- Converts Nitrogen into a usable form for plants • Food • Yogurt • Cheese • Pickles • Sour cream • Sauerkraut

26. ATB 1, 2, 3, 4, and 5 are all antibiotic disks. The clear area around the disk after 24 hours represents the “zone of inhibition”, or the area in which the bacteria cannot grow. The larger the diameter of clear area, the more effective the antibiotic. 1) Which antibiotic disk is most effective? 2) Which antibiotic disk is least effective? 3) Antibiotics are chemicals used to control _____________. Read the bottom of pg. 161 and top of pg.162 1) Explain how antibiotics are used to kill bacteria. 2) Explain how antibiotic resistance can develop.