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Download Ch 23: Bacteria - Aurora City Schools
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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 Archaea • Live in extreme environments (temperature, pressure, chemicals (methane, salt)) • Different: – Cell walls (more peptiodglycen (protein+ sugars)) – Lipids in cell membranes – DNA and RNA Classifying Bacteria • Shape: – Round (coccus) – Rod (bacillus) – Spiral (spirillum) Colonies: Strepto (chains) Staphylo (clusters) Classifying Bacteria • Gram stain – Stains outer wall, depending on structure – Gram +: purple, simple cell wall – Gram - : red, complex cell walls 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 and syphilis • Chlamydia: STD 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 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) 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 Reproduction 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 Antibacterial Resistance Good or bad? • Bad: – – – – Anthrax Tooth decay Lyme disease Staph infection Botulism Gonorrhea Salmonella Strep throat Cholera Tetanus E. coli • Good: – – – – – Food: sour cream, cheese, yogurt, pickles, Copy DNA for medicines Fight pests (Bt) Decompose Nitrogen cycle 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 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 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 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 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 Diseases & treatments • Diseases: – – – – – Chicken pox/shingles Hepatitis Flu Ebola Bird Flu AIDS Warts Meningitis SARS • 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)
