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Prokaryotes

Prokaryotes. 16.1-16.10. Phylogenic Tree of the Three Domains. Prokaryote: Bacteria & Archaea. Prokaryotes: Archaea. = Ancient Exist in harsh habitats; early Earth “Extremophiles” Thermophiles: hot springs/ volcanic vent Halophiles: salty bodies of water

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Prokaryotes

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  1. Prokaryotes 16.1-16.10

  2. Phylogenic Tree of the Three Domains Prokaryote: Bacteria & Archaea

  3. Prokaryotes: Archaea • = Ancient • Exist in harsh habitats; early Earth • “Extremophiles” • Thermophiles: hot springs/ volcanic vent • Halophiles: salty bodies of water • Methanogens” anaerobic mud; give off methane; “swamp gas” Similar to Bacteria: small size; lack most organelles; no true nucleus Similar to Eukaryotes: similar DNA sequences for ribosomes & enzymes; “junk” or intron DNA sequences (don’t code for protein); don’t respond to antibiotics (cell wall is different from proks)

  4. Prokaryotes: Early Bacteria Forms http://www.bbc.co.uk/science/earth/earth_timeline/first_life Stromatolites= cyanobacteria that grow in mats on rock-like mounds in shallow reefs; dominate oceans(3 bya) Cyanobacteria - Early aerobic bacteria; oxygenate Earth; cause mass extinction; game changer (oxygen atmosphere: ~2.5 bya)

  5. The Oxygen Revolution • ~2.4 bya • Evolution of photosynthetic cyanobacteria( ~3 bya) --> free oxygen in oceans, lakes & the atmosphere • O2 toxic to most existing organisms --> Mass Extinction • Stimulates evolution of aerobic organisms (requiring oxygen) • Some forms of anaerobic bacteria (no or low O2) still survive (muddy lake bottoms/swamps)

  6. Bacteria: Pathogens 2. Endotoxins = fragments of outer membrane act toxins; fever, aches, drop in blood pressure Meningitis - swelling of brain membranes Salmonella - food poisoning; typhoid List of bacterial infections; http://classes.midlandstech.edu/carterp/Courses/bio225/InfectiousDiseases_all_print.htm • Pathogens: disease causing bacteria How? • Secrete proteinexotoxins(poisons) Clostridium toxin --> muscle spasms/lockjaw(tetanus) S. Aureus --> multiple toxins (necrotizing tissue; vomiting, diarrhea, fever) E. Coli --> food poisons

  7. Bacteria: Pathogens (Bioweapons) • Anthrax: live in soil (farms); skin infection not harmful; inhaled = deadly • Y. pestis (Plague): bubonic (black death); pneumonic (disintegrates lungs) • Clostridium botulinum: 7 toxins; • Food poisoning • Deadliest: blocks nerve transmission; stops muscle contractions (breathing) • Diluted in botox - relax facial muscles

  8. MRSA = Methicillin-resistant Staph. AureusHard to treat staph infection;Resistant to most antibioticsCommonly starts as a skin infection (lesion/wound)Harmful in elderly; nursing home & hospitals (weakened immune systems) Superbugs: http://www.sosq.vcu.edu/videos.aspx NY Hostpitals & Superbugs: cbs news http://www.cbsnews.com/videos/cre-superbug-cases-found-in-at-least-43-states/ Antibiotics in animal feed: http://www.cbsnews.com/videos/fda-to-roll-back-use-of-antibiotics-in-beef-pork-and-poultry/

  9. Bacterial Meningitis http://www.huffingtonpost.com/2013/12/05/meningitis-princeton-uc-santa-barbara-infection-bacterial_n_4392509.html?utm_hp_ref=college&ir=College http://www.nbcnews.com/health/princeton-agrees-meningitis-vaccine-fight-outbreak-2D11616706

  10. Beneficial Uses of Bacteria • Medicine/Pharmaceutic: • Produce desired gene products (insulin) • Food: Cheese & Yogurt • Aid Digestion (probiotics) • Make vitamin K in intestines • Break down cellulose in termite guts

  11. Beneficial Uses of Bacteria • Chemical recycling: • Decomposers: replenish soil nutrients and release CO2 back to the atmosphere • N.-fixing bacteria: convert nitrogen gas in the atmosphere to an organic form usable by plants; grow on roots of beans, nuts, clover • Bioremediation: • Sewage treatment: decompose organic matter in sewage sludge • Oil spill clean-up: genetically modified digest oil • Clean old mining sites: detoxify by extracting lead & mercury,arsenic

  12. Bacteria: Shape • Cocci – spherical • Bacilli – rod-shaped • Spirilla – spiral shaped

  13. Structure & Function of Bacteria: Cell Wall • Gram + (stain): purple; thick layer of peptidoglycan retains dye • Gram( –) pink stain; thin layer of peptidglycan with outer membrane

  14. Structure & Function of Bacteria: Motility • Flagellum • Pilli • Slime secretion

  15. Bacterial Repro.: Binary Fission = DNA copied; moved to opposite ends of cell as the cell divides; occurs almost continuously; ASEXUAL • Rapid; 20 min. • Parents & Offspring genetically identical

  16. Plasmids: Loops of DNA found in some bacteria; can integrate into chromosome & be translated into proteins Can be shared b/w bacteria “R” plasmids – carry genes for antibiotic resistance

  17. Genetic Variation: Sharing Genes 1. Conjugation: 2 bacteria join thru. temporary bridge and exchange plasmids. • Can be b/w diff. species

  18. Genetic Variation: Sharing Genes • Transformation: incorporates DNA fragments (fr. dead bacteria) in surroundings into genome. 3. Transduction: Bacteriophage (virus that infects bacteria) inject fragment of DNA from previous host along w/ viral DNA

  19. Original Source of Variation: Mutation = any alteration of nucleotide sequence • Usually results in malfunction/cell death • Occasionally – translates into new beneficial trait! (antibiotic resistance)

  20. Endospores • Allow bacteria to survive harsh conditions; go into a dormant endospore form • DNA copied: one copy surrounded by a thick protective coat: outer cell disintegrates • When conditions are favorable, endospores absorb water & grow again. Ex: anthrax

  21. Modes of Nutrition

  22. Viruses & Bacteriophage: The Boundary of Life • All living things share 8 characteristics. Viruses do not meet all of these characteristics. • Attack eukaryotic cells; Bacteriophages attack prokaryotic cells. • Capable of reproducing at a very rapid rate, but only in host cell. • Responsible for many diseases • Found everywhere.

  23. Viral Structure Protein coat (capsid) surrounds viral DNA or RNA

  24. Viral Structure: Variations

  25. Viruses & Disease • Method of causing disease is very different from that of bacteria (…different treatment & prevention methods too) • Antibiotics will not work on viruses because they target specific enzymes not found in viruses or host cells • Some examples of viral diseases include: Influenza (RNA) Polio (RNA) Common cold(RNA) Hepatitis (DNA) Measles (RNA) Herpes (DNA) Mumps (RNA) Smallpox (DNA) AIDS (RNA) Rabies (RNA)

  26. Viral Infection • Invade cells; use the host cell's machinery to synthesize own macromolecules. • Reproduce in 2 ways: • 1. Lytic cycle: destroying the host cell during reproduction. • 2. Lysogenic Cycle – a parasitic type of partnership with the cell

  27. Lytic Cycle & Lysogenic Cycle

  28. Viruses are host specific – a protein on the surface of the virus has a shape that matches a molecule in the plasma membrane of its host, allowing the virus to lock onto the host cell.

  29. Proviruses DNA virus that has been inserted into a host cell chromosome.

  30. Retroviruses & HIV • Retroviruses reverse the normal DNA to RNA to protein flow • RNA viruses: RNA  DNA  protein • Reverse transcriptase catalyzes synthesis of DNA fr. RNA template • DNA intermingles w/ host DNA as a provirus making it difficult to detect

  31. Prions • Proteins that cause several diseases of the brain: Mad cow disease, Kuro, Creutzfeldt-Jacob disease (CJD) & Scrapie (in sheep) • Only infectious agent that do not contain genetic material • Normal form play important roles in helping brain function (nerve cells communication) • Abnormal prions destroy the brain • Three ways to acquire abnormal prions: • Infection with abnormal prions • Inherited genes that give rise to abnormal prions • Spontaneous genetic mutations that give rise to abnormal prions

  32. Viroids • Small strands of RNA rather than strands of protein. • Smaller than the strands of genetic info in viruses and contain no protein coat. • Replicated using host cell machinery, like viruses • Cause plant diseases: potato spindle tuber, avocado sunblotch, chrysanthemum stunt, and chrysanthemum chlorotic mottle

  33. Immune Response

  34. VACCINES: Defense Against Viral Diseases Vaccines = immunizations Made from weakened (attenuated) bacteria/viruses or parts (anitgens/ fragments) of bacteria/viruses Antigens of pathogen elicit immune response without you “getting” sick.

  35. HIV doesn’t target just any cell, it goes right for the cells that want to kill it. “Helper" T cells are HIV's primary target. These cells help direct the immune system's response to various pathogens. HIV is an RNA retro-virus that targets helper T cells. Helper T cells deplete & immune response is compromised. The virus can infect 10 billion cells a day, yet only about 1.8 billion can be replaced daily.

  36. From HIV to AIDS • During first few years (7-10) after HIV infection, person is usually asymptomatic. • During the symptomatic phase, the body has insufficient numbers of T-Cells (from normal 800-1200 /mm3 to 200/ mm3 ) to mount an immune response against infections. • Chronic diarrhea, minor mouth infections, night sweats, headache & fatigue are common • At the point when the body is unable to fight off infections, a person is said to have the disease AIDS. (Generally when count drops below 200 /mm3 ) • It is not the virus or the disease that ultimately kills a person; it is the inability to fight off something as minor as the common cold.

  37. AIDS: The Global Epidemic • Around 2.6 million people became infected with HIV in 2009. • Sub-Saharan Africa has been the hardest hit by the epidemic. In 2009 over two-thirds of AIDS deaths were in this region

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