2. Viruses and Bacteria Chapter 18

3. What is a virus? Considered non-living particles by most biologists because they: 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: Viruses are named after: –The disease they cause (poliovirus) –The organ they infect (adenovirus)

4. Viral Structure Genetic Material in the form of: Genetic Material in the form of: –DNA –RNA Capsid: outer protein coat Capsid: outer protein coat –4 common shapes  Polyhedral  Helical  Enveloped  Bacteriophage or phage

5. Polyhedral Viruses Herpes virus Herpes virus Adenovirus Adenovirus Polio virus Polio virus

6. Helical Viruses Tobacco Mosaic Virus Tobacco Mosaic Virus

7. Enveloped Viruses Contain an envelope made of Contain an envelope made of –Lipids –Carbohydrates –Proteins Examples Examples –Influenza Virus –HIV

8. Bacteriophages “phage” “phage” Is a virus that attacks bacteria Is a virus that attacks bacteria

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

10. Viral Replication Cycles Lytic Cycle Lytic Cycle –Kills the host cell Lysogenic Cycle Lysogenic Cycle –Similar to lytic cycle but does not immediately kill host cell –Viral genetic material recombines with host cell’s DNA –Provirus: Viral DNA that is integrated into host cell’s chromosome  Examples: HSV I & II, hepatitis B, and chicken pox

12. Lytic Cycle Lytic Cycle A virus attaches to a host cell. A virus attaches to a host cell. Virus releases its genetic material into the host cell. Virus releases its genetic material into the host cell. The injected genetic material recruits the host cell's enzymes. The injected genetic material recruits the host cell's enzymes. The enzymes make parts for more new viruses. The enzymes make parts for more new viruses. The new parts assemble into new viruses. The new parts assemble into new viruses. The new particles lyse (burst) the host cell and exit. The new particles lyse (burst) the host cell and exit.

13. Lysogenic Cycle

15. Retroviruses Type of RNA virus that reverse transcribes itself into DNA Type of RNA virus that reverse transcribes itself into DNA The newly transcribed DNA inserts into host’s DNA The newly transcribed DNA inserts into host’s DNA Ex: HIV Ex: HIV

16. Prokaryotes Unicellular organisms without membrane- bound organelles Unicellular organisms without membrane- bound organelles 2 Kingdoms 2 Kingdoms –Archaebacteria –Eubacteria

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

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

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

20. Eubacteria: Chemosythetic Autotrophs Break down and release energy from inorganic compounds such as H 2 S Break down and release energy from inorganic compounds such as H 2 S Important in converting atmospheric nitrogen into usable forms plants need Important in converting atmospheric nitrogen into usable forms plants need –Nitrogen Fixation

21. Structure

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

23. Identifying Bacteria: Shapes

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

25. Bacterial Reproduction Sexually by conjugation Sexually by conjugation

26. Common Bacterial Diseases DiseaseAgentSymptomsTreatment Strep Throat Streptococcus pyogenes sore throat, fever antibiotic Tetanus C. tetani stiff jaw, muscle spasm, paralysis antibiotic, clean wound Tuberculosis M. tuberculosis chronic cough, chest pain, blood in sputum antibiotic Dental Caries S. mutans toothache remove decay Botulism C. botulinum blurred vision, paralysis, slurred speach antitoxins Cholera Vibrio cholera diarrhea, vomiting re-hydration, antibiotic Traveler's Diarrhea Escherichia coli stomach cramps, diarrhea re-hydration, antibiotic

27. Beneficial Bacteria Nitrogen Fixation Nitrogen Fixation N 2 → NO 2 - + NO 3 - N 2 → NO 2 - + NO 3 - Converts Nitrogen into a usable form for plants Food Food –Yogurt –Cheese –Pickles –Sour cream –Sauerkraut