prokaryotes
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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 - PowerPoint PPT PresentationTRANSCRIPT
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ProkaryotesProkaryotes16.1-16.10
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Phylogenic Tree of the Three Domains
Prokaryote: Bacteria & Archaea
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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)
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Prokaryotes: Early Bacteria Forms
• 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)
http://www.bbc.co.uk/science/earth/earth_timeline/first_life
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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)
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Bacteria: Pathogens
• Pathogens: disease causing bacteriaHow?1. Secrete protein exotoxins (poisons)
Clostridium toxin --> muscle spasms/lockjaw(tetanus)
S. Aureus --> multiple toxins (necrotizing tissue; vomiting, diarrhea, fever)
E. Coli --> food poisons
2. Endotoxins = fragments of outer membrane act toxins; fever, aches, drop in blood pressure
Meningitis - swelling of brain membranes
Salmonella - food poisoning; typhoidList of bacterial infections;
http://classes.midlandstech.edu/carterp/Courses/bio225/InfectiousDiseases_all_print.htm
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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
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MRSA = Methicillin-resistant
Staph. Aureus
Hard to treat staph infection;
Resistant to most antibiotics
Commonly starts as a skin infection (lesion/wound)
Harmful in elderly; nursing home & hospitals (weakened
immune systems)Superbugs: http://www.sosq.vcu.edu/videos.aspxNY 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/
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Bacterial Meningitis
http://www.huffingtonpost.com/2013/12/05/meningitis-princeton-uc-santa-barbara-infection-bacterial_n_4392509.html?utm_hp_ref=college&ir=Collegehttp://www.nbcnews.com/health/princeton-agrees-meningitis-vaccine-fight-outbreak-2D11616706
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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
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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
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Bacteria: Shape• Cocci – spherical • Bacilli – rod-shaped• Spirilla – spiral shaped
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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
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Structure & Function of Bacteria: Motility
• Flagellum• Pilli• Slime secretion
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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
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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
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Genetic Variation: Sharing Genes 1. Conjugation: 2 bacteria join thru. temporary bridge and exchange plasmids.•Can be b/w diff. species
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Genetic Variation: Sharing Genes
2. 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
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Original Source of Variation: Mutation
= any alteration of nucleotide sequence •Usually results in malfunction/cell death
•Occasionally – translates into new beneficial trait! (antibiotic resistance)
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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
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Modes of Nutrition
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• 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.
Viruses & Bacteriophage: The Boundary of Life
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Viral Structure
Protein coat (capsid) surrounds viral DNA or RNA
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Viral Structure: Variations
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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)
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Viral InfectionViral 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
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Lytic Cycle & Lysogenic CycleLytic Cycle & Lysogenic Cycle
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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.
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ProvirusesProvirusesDNA virus that has been inserted into a host cell chromosome.
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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
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Prions 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
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ViroidsViroids• 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
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Immune Response
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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.
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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.
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From HIV to AIDSFrom 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.
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AIDS: The Global EpidemicAIDS: 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