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Prokaryotes Virus APBio
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Prokaryotes Virus APBio


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  • Transcript

    • 1. Prokaryotes and Viruses
    • 2. Prokaryotic Domains
      • Single-cell microbes
      • Lack most organelles (membrane bound)
      • Inhabit diverse environments
      • Differences between Bacteria and Archaea
        • Structural and biochemical features
          • Archaea have histones (just like Eukarya)
          • Differences in cell walls, plasma membrane composition, ribosomes, and RNA polymerases
    • 3. The Sizes of Microorganisms 1 µ m Eukaryotic Cells (10-100 µ m) Prokaryotic Cells (0.2-10 µ m) Staphylococcus Cyanobacterium Escherichia coli Viruses (0.05-0.2 µ m)
    • 4. Classifying Prokaryotes Is Difficult
      • Features used in prokaryotic classification:
        • Shape
        • Means of locomotion
        • Pigments
        • Nutrient requirements
        • Colony appearance
        • Gram staining characteristics
        • Nucleotide sequences
    • 5. Three Common Bacterial Shapes (a) (b) (c)
    • 6. Bacterial Characteristics
      • Shape - cocci, bacilli, spirilla
        • Cell wall - peptidoglycan
        • Capsules or slime layer - polysaccharide or protein chains
        • Pili - protein form of attachment
        • Flagella - used to propel by rotation
      • Endospores (some bacteria)
        • Contain nucleic acid surrounded by a protein coat
        • Form in inhospitable environments
        • Reside dormant until favorable environment; Can last for years
        • Great mechanism for continuing species
    • 7.  
    • 8. Diverse Metabolisms
      • Anaerobic Metabolism
        • Some bacteria live without oxygen (and are poisoned by it)
          • e.g. Tetanus bacteria
        • Some bacteria can switch between aerobic and anaerobic respiration
          • e.g. Escherichia coli in our large intestines
    • 9. Diverse Metabolisms
      • Where bacteria get their energy
        • Familiar organic compounds
          • Sugars, carbohydrates, fats, and proteins
        • Compounds poisonous to humans
          • Petroleum, methane, benzene, toluene
        • Inorganic molecules
          • Hydrogen, sulfur, ammonia, iron, nitrite
      • Some bacteria get energy from sunlight
        • Cyanobacteria perform photosynthesis
        • Sulfur bacteria use H 2 S instead of water in photosynthesis
    • 10. Binary Fission
      • Asexual cell division produces identical copies
      • Binary fission can occur every 20 minutes
      • Rapid reproductive rate allows for rapid evolution
        • Mutations in DNA replication are rapidly spread
    • 11.  
    • 12. Exchange of Genetic Material
      • Conjugation allows for DNA transfer between donor and recipient
      • Sex pilus connects donor to recipient cell forming a cytoplasmic bridge
      • Conjugation can occur between different species
      • Small circular DNA molecules ( plasmids ) carry genes from donor to recipient
    • 13. Conjugation: Prokayotic “Mating” Sex Pilus Donor Recipient
    • 14. Benefits of Bacteria
      • Cyanobacteria
        • Photosynthesis
        • Pioneers in primary succession
      • Chemosynthesis - nutrient cycles and plants
      • Symbiosis - living together
        • Ruminants’ digestive tracts
        • Nitrogen fixing in certain legumes
        • Bacteria on the human body
      • Biodegradation - oil
      • Food production - cheese, yogurt, sauerkraut
      • Decomposers
    • 15. Bacterial Pathogens
      • Small number of species cause disease
      • Survey of human bacterial diseases
        • Anaerobes - toxins (tetanus, botulism)
        • Allergic reactions - Streptococcus pneumoniae
          • Pneumonia
          • "Flesh-eating" bacteria
        • Black Death, tuberculosis
        • Sexually transmitted diseases
          • Gonorrhea
          • Syphilis
    • 16. The Prokaryote Flagellum (b)
    • 17. Bacterial Habits
      • Habitats
        • Bacteria inhabit nearly every habitat
        • Bacteria are specialists
    • 18. Archaea
      • Unique lipid membranes, cell walls, and rRNA
      • Methanogens
        • Convert CO 2 to methane
        • Swamps, hot springs, vent communities, cow stomachs
      • Halophiles - survive concentrated salt environment
      • Thermoacidophiles - thrive in hot, acidic environment
    • 19. Some Prokaryotes Thrive in Extreme Conditions
    • 20. Nitrogen-Fixing Bacteria on Root Nodules (a) (b)
    • 21. Nonliving Parasitic Molecules
      • Viruses
        • Nucleic acid molecule surrounded by a protein coat
        • Bacteriophages; viruses that infect bacteria
        • Survey of human viral diseases
      • Viroids
        • Short strands of RNA without a protein coat
        • Cause disease mostly in plants; affect some crops
      • Prions
        • Proteinaceous infectious particle
        • Human prion diseases
    • 22. Viruses
      • Two major components constitute a virus
        • Single or double-stranded DNA or RNA as hereditary material
        • Protein coat
          • May be surrounded by an envelope formed from the plasma membrane of the host cell
      • Cannot grow or reproduce on their own and are parasites of living cells
      • Have a specialized protein coat that enables entry into a host cell…
    • 23. Viruses
      • Viral genetic material “hijacks” host cell to produce new viral components
      • Viral components assemble rapidly into new viruses and burst from host cell
    • 24. Viral Structure and Replication (a) Glycoproteins Envelope (lipid bilayer) Protein Coat Core Proteins Reverse Transcriptase Viral RNA in protein coat Spikes Herpes Viruses HIV (b)
    • 25. Viruses Come in Many Shapes Rabies Measles Bacteriophage Herpes Tobacco Mosaic
    • 26. Viruses Are Host-Specific
      • Each viral type specialized to attack specific host cell
      • Bacteriophages can treat bacterial diseases
        • Rise in bacterial antibiotic resistance makes standard drugs less effective
        • Bacteriophages specifically target host bacteria
        • Bacteriophages are harmless to human body cells
    • 27. Viruses Are Host-Specific
      • In multicellular organisms viruses specialize in attacking particular cell types
      • Cold viruses attack membranes of respiratory tract
      • Measles viruses infect the skin
      • Rabies viruses attack nerve cells
    • 28. Viruses Are Host-Specific
      • Some viruses linked to cancer (e.g. T-cell leukemia, liver cancer, cervical cancer)
      • Herpes virus attacks mucous membranes of mouth and lips (causing cold sores)
        • Other herpes virus type causes genital sores
      • HIV virus attacks specific white blood cell type, causing AIDS
    • 29. Some Viruses Infect Bacteria Bacterium Newly forming bacteriophages
    • 30. How Viruses Replicate: HIV (a) cytoplasm nucleus DNA vRNA mRNA 1a. Virus attaches to receptor 2. Viral reverse transcriptase makes DNA using viral RNA 1b. Core disintegrates; viral RNA enters the cytoplasm 3a. DNA enters nucleus & chromosomes 3b. DNA transcribed into mRNA & viral RNA, which move to cytoplasm
    • 31. How Viruses Replicate: HIV (b) 4. Viral proteins made using mRNA 5. Viral proteins & RNA assembled 6. Viruses bud from plasma membrane
    • 32. How Viruses Replicate: Herpes (a) (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
    • 33. How Viruses Replicate: Herpes (b) nucleus mRNA (cytoplasm) envelope coat DNA 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
    • 34. Viral Infections Are Difficult to Treat
      • Antibiotics against bacteria are infective against viruses
      • Antiviral drugs may also kill host cells
      • Viruses “hide” within cells, are hard to detect
      • Viruses have high mutation rates
        • Mutations can confer resistance to antiviral drug
        • Resistant viruses spread and multiply, rendering drug ineffective
    • 35. Viroids
      • Viroids are infectious particles with only short RNA strands (no protein coat)
      • Able to enter host cell nucleus and direct new viroid synthesis
      • A number of crop diseases are caused by viroids
        • e.g. cucumber pale fruit disease, avocado sunblotch, potato spindle tuber disease
    • 36. Prions
      • A mutated protein that acts as an infectious agent
      • Fatal degenerative disease discovered in New Guinea tribe (Fore) in 1950
      • Kuru causes loss of coordination, dementia, death
      • Kuru in the Fore tribe was transmitted by ritual cannibalism of the dead
    • 37. Prions
      • Other diseases like kuru include:
        • Creutzfeldt-Jacob (CJD) disease in humans
        • Scrapie in sheep
        • Bovine spongiform encephalopathy (BSE or “Mad Cow Disease”) in cattle
      • These diseases create holes in brain tissue
    • 38. Prions: Puzzling Proteins
    • 39. The End