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LECTURE NOTES – 2007, BLY 122, O’BRIEN I. Bacteria and Archaea (Chapter 27) A. Characteristics of Bacteria & Archaea compared to Eukaryotes (See Table 27.2) 1. Characteristics common to Bacteria & Archaea (Two together are known as “prokaryotes”) a) No membrane-bound organelles (1) No chloroplasts (2) No mitochondria (3) No nucleus b) One circular chromosome 2. Both Archaea & Eukaryotes have many complex RNA polymerases 3. Archaea have unique cell walls that lack peptidogylcan (= proteinsugar complexes) found in bacterial cell walls Picture Slide: Figure 27.12a 4. Eukaryotes a) Characteristics (1) Cell have organelles surrounded by membranes (2) Cells have nuclei b) Most multi-celled animals and plants are eukaryotes c) However, most eukaryotes are single-celled organisms known as . . . (1) Protists (2) Protistans (3) Protozoans 5. Fossil record a) Earth approximately 4.5 billion years old b) Bacteria were present 3.4 billion years ago c) Archaea & eukaryotes appeared about 1.7 billion years ago B. Bacterial Diseases 1. Koch’s postulates developed in late 1800s a) Pathogen must be present in sick organisms and absent from healthy ones b) Pathogen must be isolated and cultured from sick organism c) Symptoms of disease appear in healthy host following infection with cultured pathogen d) Pathogen must be isolated from experimentally infected host. 2. Significance of Koch’s postulates a) Established modern era of medicine b) Basis for germ theory of infectious diseases 3. Some alternative theories explaining illness a) Imbalance of body fluids (1) Humoral Theory of ancient Greeks 1 (a) Phlegm - Phlegmatic people are not easily aroused (b) Blood or sanguis - Sanguine people are cheerful and have sturdy temperaments (c) Yellow Bile or choler - Choleric people are hot-tempered (d) Black Bile or melancholia - Melancholy means sad. Picture Slide: Hippocratic Doctrine of 4 Fluids (Picture not in text) (2) Blood-letting removes “bad blood” Picture Slide: Blood-letting using a leech (Picture not in text) b) Imbalance of body energies (1) Acupuncture attempts to restore balanced of yinyang (2) Chiropractic medicine attempts to restore nerve activity c) Possession by evil spirits d) Punishment for transgressions 4. Indiscriminate use of antibiotics a) Resistance to antibiotics is increasing b) Antibiotics only affect bacteria, not viruses Word Slide: “ …The landmark pink hospital, Tripler Army Medical Center in Honolulu, bustles with modern medicine and coordinated public health, and if you want to find explosive evolution, you should look in a place like this. Here you will find tuberculosis that has resisted treatment, strep throats that have shrugged off erythromycin, and a chilling post-operative infection called methicillin-resistant Staphylococcus aureus that can slip into a recovery room and kill after surgery. AIDS patients arrive for checkups, each carrying with them a self-contained arms race between their immune system and HIV, a race that runs on evolutionary fuel, with a grim finish line. . . . No hospital in the world can ignore drug resistance, and drug resistance is evolution come to life.” From Stephen Palumbi, S.R. (2001) The Evolution Explosion: How Humans Cause Rapid Evolutionary Change, W.W. Norton & Co.; p. 5 C. D. E. Global Change 1. Cyanobacteria photosynthesis probably produced the first significant amounts of oxygen gas on earth Picture Slide: Fig. 27.3 2. Bacteria & Archaea carry out mineral nutrient recycling upon which all organisms depend a) Plant growth often limited by availability of nitrogen b) Bacteria and Archaea only known organisms that can fix nitrogen (= convert nitrogen gas to a form that can be used by eukaryotes) Picture Slide: Fig. 27.14 Phylogeny of bacteria, Archaea & eukaryotes 1. Morphological differences between prokaryotic cells are minimal 2. Phylogeny accepted today was determined by comparison of ribosomal RNA gene sequences Picture Slide: Compare Fig. 27.1 with Fig. 27.9 a) Bacteria diverged first b) Archaea more closely related to eukaryotes than to bacteria Morphological Diversity 2 1. Gram-positive bacteria have a cell wall with abundant peptidoglycan. Picture Slide: Fig. 27.12a 2. Gram-negative bacteria have thin, gelatinous cell wall with peptidoglycan surrounded by a phospholipid bilayer. Picture Slide Fig. 27.12b 3. These two can be distinguished by a Gram stain that reacts with the peptidoglycan. Picture Slide Fig. 27.12c a) The Gram stain colors the cell wall of Gram-positive bacteria purple. b) The Gram stain cannot reach the peptidoglycan in the Gram-negative cell wall, so it stains pink. F. Metabolic Diversity is Greatest in Prokaryotes 1. Eukaryotes a) Plants use one biochemical system to synthesize sugar from carbon dioxide b) Animals cannot convert CO2 to sugar c) Animals can only obtain carbon from other organisms 2. Bacteria and Archaea a) Obtain carbon from organic and inorganic sources b) Use many different electron donors and electron acceptors for ATP synthesis Picture Slides: Fig. 27.13 & Table 27.4) (1) Use light (2) Organic compounds (3) Inorganic compounds Picture Slides: Methane Seep Organisms in the Gulf of Mexico form symbiotic associations with methanotrophic bacteria; From McDonald & Fisher, National Geographic 1996, 190(4); 95 (Figures not in text) G. Key Lingeages 1. Spirochaeles Bacteria Picture Slide: Fig. 27.16 a. Corkscrew shape b. Syphilis and Lyme disease are caused by spirochetes 2. Chlamydiales Picture Slides Fig. 27.17 a. All species are endosymbionts and live in hosts b. Chlamydia trachomatis infections cause blindness and urogenital infections if passed via intercourse. 3. High-GC Gram positives Picture Slide: Fig. 27.18 a. DNA with a high guanine and cytosine content. b. Over 500 antibiotics have been isolated from species in genus Streptomyces. c. Tuberculosis and leprosy are caused by species from this group. d. Species in this group live in plant roots and fix nitrogen. 4. Cyanobacteria Picture Slide: Fig. 27.19 a. All perform oxygenic photosynthesis. b. Some can fix nitrogen. c. Produce much of the oxygen and nitrogen that other species need. d. A few species live with fungi, forming lichens. 3