ch 23: bacteria are prokaryotes: – unicellular – no membrane-bound organelles (nucleus, er,...
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Ch 23: Bacteria
• Are prokaryotes:– Unicellular– No membrane-bound organelles
(nucleus, ER, lysosomes)
• Live nearly everywhere… in/on other organisms, in ice, in hot springs,
at the bottom of the ocean, in rocks, soil, air
• 2 main kinds: Eubacteria and Archaea
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Archaea
• Live in extreme environments (temperature, pressure, chemicals (methane, salt))
• Different:– Cell walls (more peptiodglycen (protein+
sugars))– Lipids in cell membranes– DNA and RNA
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Classifying Bacteria
• Shape: Colonies:– Round (coccus) Strepto (chains)– Rod (bacillus) Staphylo– Spiral (spirillum) (clusters)
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Classifying Bacteria
• Gram stain– Stains outer wall, depending on structure– Gram +: purple, simple cell wall– Gram - : red, complex cell walls
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Impact on humans:
• Proteobacteria: live in soil and make nitrogen usable by living things
• Gram +: cause disease (botulism, anthrax), make food (yogurt, sour cream), make antibiotics
• Cyanobacteria: makes oxygen, food for aquatic food chains
• Spirochetes: cause Lyme Disease andsyphilis
• Chlamydia: STD
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Structures and functions
• Outside:– Up to 3 layers:• Cell membrane: lets things in and out• Cell wall (different makeup than plants):
structure• Capsule (maybe): helps stick together
–Movement:• Flagella: long whip like tail, may have many• Cilia: small hairs-like structures
– Pili: small structures for reproduction
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Structures and functions
• Inside– Cytoplasm: where most cell functions take
place, since no organelles– Ribsomes: make proteins– DNA: in a loop
• Plasmid, small separate piece of DNA
• Getting oxygen:– Some bacteria have to have: (obligate
aerobes)– Some have to not have (obligate anaerobes)– Some can live with or without (facultative
anaerobes)
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Reproduction• Asexually: Binary fission– DNA ring copies (2 only replication forks)
and cell splits in two
• Sexually:– Conjugation: exchange DNA with
another bacterium through pili– Transformation: take in DNA in
environment (usu. from dead bacteria)
– Transduction: get new DNA from a virus
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Reproduction
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Bacteria and Health
• Sometimes it releases chemicals while it’s alive (exotoxins), sometimes after it’s dead (endotoxins)
• Antibiotics: medicines that fight bacterial diseases. Make cell wall stop growing so bacterium “pops”
• Population can become resistance to antibiotics by mutation or by not finishing whole course of medications
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Antibacterial Resistance
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Good or bad?
• Bad:– Anthrax Botulism Cholera– Tooth decay Gonorrhea Tetanus– Lyme disease Salmonella E. coli– Staph infectionStrep throat
• Good:– Food: sour cream, cheese, yogurt, pickles, – Copy DNA for medicines– Fight pests (Bt)– Decompose– Nitrogen cycle
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Ch 24: Viruses• Not considered alive:– Don’t reproduce on own– don’t metabolize– don’t grow/develop– don’t perform homeostasis– don’t respond to environment
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Structure/classification
• Vary greatly in structure/shape– DNA or RNA – Surrounded by capsid (protein coat)– Some surrounded by bilipid envelope
• Classified by:– DNA or RNA– Single or double strand– Linear or circular– Shape of capsid
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Replication
• Viruses injects DNA/RNA, takes over the cell, makes the cell make
more viruses, Kills cell when new viruses released infects more cells
• 2 cycles:– Lytic: happens fast, virus kills cells,
virulent phages– Lysogenic: happens slow…days, weeks,
months, years. Virus “hides” in the cell as part of cell’s genome, then enters lytic
cycle, temperate phages
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Lytic cycle• Virulent phage: happens quickly
– Viruses injects DNA/RNA– takes over the cell, makes the cell make more viruses– Kills the cell when viruses released to infect more cells
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Lysogenic cycle• Temperate phage: happens slowly…days, weeks,
months, years. – Virus “hides” in the cell as part of cell’s genome– then enters lytic cycle and kills cells
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Diseases & treatments
• Diseases:– Chicken pox/shingles AIDS– Hepatitis Warts– Flu Meningitis– Ebola SARS– Bird Flu
• Treatments:– Vaccines: give inactive virus or parts of virus,
helps immune system recognize and respond faster
– Control vector: if spread by animal, kill animal– Antiviral drugs (few available)