1. The World of Microbes: Viruses & Bacteria AP Biology Chapter 23

2. Microbes are… Viruses Viruses Bacteria Bacteria Protists Protists Microbiology is the study of microbes! Microbiology is the study of microbes!

3. Small is Relative! 1µm1µm1µm1µm Eukaryotic Cells (10-100 µ m) Prokaryotic Cells (0.2-10 µ m) Staphylococcus Cyanobacterium Escheria coli Viruses (0.05-0.2 µ m)

4. Viruses

5. Viruses Viruses DNA or RNA surrounded by a protein coatDNA or RNA surrounded by a protein coat Parasitic - require a host cell (like cells of your body) to replicateParasitic - require a host cell (like cells of your body) to replicate Infect all kinds of organisms:Infect all kinds of organisms: Bacteria Bacteria Plant cells Plant cells Animal cells Animal cells Some viruses only affect certain parts of their hostsSome viruses only affect certain parts of their hosts ex. Rabies affects nervous system ex. Rabies affects nervous systemViruses

6. Are Viruses Alive? Viruses are not regarded as living organisms; lack some attributes of life. Viruses are not regarded as living organisms; lack some attributes of life. Are infectious particles, incapable of replicating independently.Are infectious particles, incapable of replicating independently. Lack cellular organization and metabolism.Lack cellular organization and metabolism.

7. Viruses Replication Replication Viruses reproduce only inside living cells.Viruses reproduce only inside living cells. Viruses replicate by infecting susceptible cells and using the cell to make more viruses.Viruses replicate by infecting susceptible cells and using the cell to make more viruses.

8. Viruses Various illnesses: Various illnesses: flu, AIDS, common cold flu, AIDS, common cold Some antiviral medicines Some antiviral medicines Evolve very, very, rapidly Evolve very, very, rapidly Makes effective treatment difficult Makes effective treatment difficult Each virus has a host range Each virus has a host range A limited number of host cells that it can infect A limited number of host cells that it can infect

9. Virus Shape Viral shape is determined by the nature of the virus’s protein coat. Viral shape is determined by the nature of the virus’s protein coat. Viruses such as the rabies and herpes viruses are surrounded by an extra envelope derived from membranes of the host cell. Viruses such as the rabies and herpes viruses are surrounded by an extra envelope derived from membranes of the host cell.

10. Viruses Come in Many Shapes Rabies Measles Bacteriophage Herpes Tobacco Mosaic

11. Viruses infect bacteria

12. Bacteriophages Viruses called bacteriophages Viruses called bacteriophages Can infect and set in motion a genetic takeover of bacteria, such as Escherichia coliCan infect and set in motion a genetic takeover of bacteria, such as Escherichia coli

13. Bacteriophages Infect Bacteria Bacterium Newly forming bacteriophages

14. In this electron micrograph, bacteriophages are seen attacking a bacterium. In this electron micrograph, bacteriophages are seen attacking a bacterium. They have injected their genetic material inside, leaving their protein coats clinging to the bacterial cell wall. They have injected their genetic material inside, leaving their protein coats clinging to the bacterial cell wall. The black objects inside the bacterium are newly forming viruses. The black objects inside the bacterium are newly forming viruses.

15. Viral Structure - Envelope (lipid bilayer) Envelope (lipid bilayer) Protein Coat Protein Coat Core Proteins Core Proteins Reverse Transcriptase Reverse Transcriptase Genetic Material 2 RNA molecules Genetic Material 2 RNA molecules Receptor Receptor HIVHIV

16. Cross section of the virus that causes AIDS Inside is genetic material surrounded by a protein coat and molecules of reverse transcriptase, an enzyme that catalyzes the transcription of DNA from the viral RNA template after the virus enters the host cell. Inside is genetic material surrounded by a protein coat and molecules of reverse transcriptase, an enzyme that catalyzes the transcription of DNA from the viral RNA template after the virus enters the host cell. HIV is among those that also have an outer envelope that is formed from the host cell’s plasma membrane. Spikes made of glycoprotein (protein and carbohydrate) project from the envelope and help the virus attach to its host cell. HIV is among those that also have an outer envelope that is formed from the host cell’s plasma membrane. Spikes made of glycoprotein (protein and carbohydrate) project from the envelope and help the virus attach to its host cell.

17. Herpes Virus Herpes Viruses Envelope (lipid bilayer) Envelope (lipid bilayer) Protein Coat Protein Coat Viral DNA in protein coat Viral DNA in protein coat

18. How Viruses Replicate: Herpes (cytoplasm) envelope coat DNA nucleus DNA mRNA 1.Virus enters cell by endocytosis 3.Viral DNA transcribed to mRNA, which moves to cytoplasm 2a.Viral envelope merges with nuclear membrane 2b.Protein coat disintegrates; viral DNA copied & enters nucleus

19. How Viruses Replicate: Herpes nucleus mRNA (cytoplasm) envelope coat DNA mRNA 4.MRNA makes proteins, which enter nucleus 5.New viruses assembled & bud from nucleus, get envelope from inner nuclear membrane 6.Newly formed viruses leave the cell by exocytosis

20. Herpes Virus Viruses such as the herpes virus can remain hidden in the cell for a long time without reproducing. Viruses such as the herpes virus can remain hidden in the cell for a long time without reproducing. Ex. Herpes virus that causes cold soresEx. Herpes virus that causes cold sores No symptoms appear until something causes the virus to be active, No symptoms appear until something causes the virus to be active, such as a fever or sunburn.such as a fever or sunburn. As long as the virus does not reproduce, there are no symptoms. As long as the virus does not reproduce, there are no symptoms. When the virus reproduces again, the cold sores reappear. When the virus reproduces again, the cold sores reappear.

21. Viruses Diseases caused by viruses are hard to treat or cure. Diseases caused by viruses are hard to treat or cure. There are no known drugs to destroy viruses, although some may be effective in temporarily treating them. There are no known drugs to destroy viruses, although some may be effective in temporarily treating them. The white blood cells of the Immune System may surround a destroy a virus. The white blood cells of the Immune System may surround a destroy a virus. Antibodies may help destroy viruses. Antibodies may help destroy viruses. Antibodies only act on one specific kind of virus.Antibodies only act on one specific kind of virus.

22. Viruses Vaccines Harmless substances made from weakened or dead viruses Stimulate the immune system to create defenses (antibodies) against the actual pathogen Can prevent certain viral illnesses Examples: chicken pox, flu, measles, mumps, rubella, hepatitis

24. Prokaryotes: Archaea & Bacteria

25. The Tree of Life All living things classified in three domains: All living things classified in three domains: BacteriaBacteria ArchaeaArchaea EukaryaEukarya

26. Amazing Living Things Microbes indispensable to life: Produce much of Earth’s: Oxygen Decomposition Over half of Earth’s biomass More bacterial cells than human cells in your body!

27. Prokaryotes Prokaryotes have: Prokaryotes have: Circular DNA, RNA, ribosomes, cytoplasm, plasma membraneCircular DNA, RNA, ribosomes, cytoplasm, plasma membrane Most prokaryotes have a cell wall, a capsule (around the cell wall) and a flagellumMost prokaryotes have a cell wall, a capsule (around the cell wall) and a flagellum Prokaryotes don’t have: Prokaryotes don’t have: Organelles such as nucleus, chloroplasts, mitochondria.Organelles such as nucleus, chloroplasts, mitochondria.

28. Generalized Prokaryote Capsule Cell Wall Plasma Membrane Cytosol Nucleoid DNA Flagellum Plasmid DNA

29. Prokaryotic DNA The area that contains the genetic material is referred to as the nucleoid. The area that contains the genetic material is referred to as the nucleoid. The genes are usually in one continuous circular loop of DNA. The genes are usually in one continuous circular loop of DNA. There may be other small circles of DNA outside the nulceoid called plasmids. There may be other small circles of DNA outside the nulceoid called plasmids.

30. Bacteria/Archaea Habitats (name a place, and they live there!) Habitats (name a place, and they live there!) They are specialistsThey are specialists human skin, mouth, respiratory tract, large intestine, urogenital tract, etc. human skin, mouth, respiratory tract, large intestine, urogenital tract, etc. salty Dead Sea salty Dead Sea extreme pH extreme pH archea in deep sea vents: 90-106 o C archea in deep sea vents: 90-106 o C Aerobes and anaerobesAerobes and anaerobes

31. Some Prokaryotes Thrive in Extreme Conditions Cyanobacteria in Yellowstone Hot Springs

32. Archaea Unique lipid membranes, cell walls, and rRNA Unique lipid membranes, cell walls, and rRNA Methanogens Methanogens Convert CO 2 to methaneConvert CO 2 to methane Swamps, hot springs, vent communities, cow stomachsSwamps, hot springs, vent communities, cow stomachs Halophiles - survive concentrated salt environment Halophiles - survive concentrated salt environment Thermoacidophiles - thrive in hot, acidic environment Thermoacidophiles - thrive in hot, acidic environment Generally in EXTREME environments Generally in EXTREME environments

33. Bacteria Evolve Rapidly Most of the time are asexual Classified by shape, locomotion, pigments, nutrients, colonies

34. Bacteria Shape: Cocci - round Bacilli - rod Spirilla - spirals

35. Three Common Bacterial Shapes (a) (b) (c) cocci spirillus bacillus

36. The Prokaryote Flagellum Bacterium Flagella

37. Bacteria Reproduction Reproduction is asexual, by simple splitting (binary fission) Daughter cells are genetic clones of the parent cell

38. Binary Fission DNA

39. Bacteria - Reproduction Binary fission: Binary fission: Very fast, up to once every 20 minutesVery fast, up to once every 20 minutes One bacterium-> 10 21 in 24 hours.One bacterium-> 10 21 in 24 hours. Conjugation : (sexual reproduction) Conjugation : (sexual reproduction) Used only occasionally.Used only occasionally.

40. Bacteria – Sexual Reproduction Conjugation: Genetic variation through pili (structures similar to flagella) and plasmid DNA DNA is exchanged between bacterial cells Occurs through a special large, hollow pilus One bacterium acts as a donor, transferring DNA to the recipient.

41. Conjugation Sex Pilus Donor Recipient

42. Benefits of Bacteria Symbiosis (mutualism) Symbiosis (mutualism) Ruminants’ digestive tractsRuminants’ digestive tracts Nitrogen fixing in soil, nodules on certain legumesNitrogen fixing in soil, nodules on certain legumes Bacteria on/in the human body: intestines and vitamin K and B12Bacteria on/in the human body: intestines and vitamin K and B12 Biodegradation - oil Biodegradation - oil Food production - cheese, yogurt, sauerkraut Food production - cheese, yogurt, sauerkraut Decomposers Decomposers

43. Our Relationship With Bacteria

44. Bacterial Pathogens Some cause disease = pathogenic In humans: Strep throat Toxins - tetanus, botulism Pneumonia "Flesh-eating" bacteria Plague Tuberculosis Cholera Lyme disease ANTIBIOTICS= anti bacterial!!!

45. The Causes of Tooth Decay

46. Transmission of Bacterial Pathogens Airborne Airborne Water Water Food Food Direct (skin contact, blood, and other body fluids) Direct (skin contact, blood, and other body fluids) Insect vectors and other hosts such as deer tick (Lyme) or mosquito. Insect vectors and other hosts such as deer tick (Lyme) or mosquito.

47. Germ Theory of Disease Theory that microorganisms are the cause of disease. Theory that microorganisms are the cause of disease. 1859 – Louis Pasteur 1859 – Louis Pasteur Credited with the idea that human diseases were caused by bacteria and viruses (germ theory)Credited with the idea that human diseases were caused by bacteria and viruses (germ theory) Very important discovery in the field of medicineVery important discovery in the field of medicine Also created vaccinations to prevent diseaseAlso created vaccinations to prevent disease

48. Infectious Diseases Average age of death, in first world countries, jumped 30+ years in last century due to antibiotics, and enhanced hygiene and nutrition. Average age of death, in first world countries, jumped 30+ years in last century due to antibiotics, and enhanced hygiene and nutrition. Antibiotic-resistant infections on the rise in hospitals in the U.S. Antibiotic-resistant infections on the rise in hospitals in the U.S. This is due to bacterial evolution in response to widespread use of antibiotics!This is due to bacterial evolution in response to widespread use of antibiotics!