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Unformatted text preview: Prokaryotes I. Taxonomy and Systematics systematics - the branch of science that deals with organizing organisms into groups according to evolutionary relatedness. Example: a domestic cat - Felis cattus a bobcat - Felis lynx The grouping progresses to broader categories of classification: family, orders, classes, subphyla, phyla (or divisions), kingdoms, domains Five kingdoms are recognized: Monera, Protista, Fungi, Plantae, Animaliae II. Domain Bacteria, Kingdom Monera A. Characteristics 1. Prokaryotes were the first type of cells to evolve. Fossils date back to 3.5 billion years ago. stromatolites - coulmn-like deposits of cyanobacteria that took in calcium carbonate and other minerals. Stromatolites are still forming in certain places such as Australia and Yellowstone National Park. Fig. 27-3 Carbohydrate portion of lipopolysaccharide Peptidoglycan Outer membrane Cell wall layer Cell wall Plasma membrane Protein Grampositive bacteria (a) Gram-positive: peptidoglycan traps crystal violet. Peptidoglycan layer Plasma membrane Protein Gramnegative bacteria 20 µm (b) Gram-negative: crystal violet is easily rinsed away, revealing red dye. Gram-positive bacteria have a thick layer of peptidoglycan. These bacteria retain the crystal violet stain of the Gram stain. Gram-negative bacteria have a thin layer of peptidoglycan. In addition, they have a protein-lipid outer membrane that Gram-positive bacteria do not have. These bacteria do not retain the crystal violoet dye of the Gram stain and instead appear red due to the final safranin stain. 4. capsule Gelatinous protective layer secreted outside of cell wall. Provides protection, including resistance of pathogenic prokaryotes to host defenses. Fig. 27-4 200 nm Capsule Fig. 27-5 Fimbriae
200 nm Fig. 27-6 Flagellum Filament
50 nm Cell wall Hook Basal apparatus Plasma membrane Fig. 27-9 Endospore 0.3 µm a. cocci (coccus, singular) - spherical Bacteria with this shape are the most varied in arrangement of cells. Arrangements: single pairs - diplococci chains - streptococci clusters - staphylococci octets - sarcina b. bacilli (bacillus, singular) - rodlike Endospore formation is more common in this group of bacteria. Arrangements: single chains (end-to-end) - streptobacilli c. spiral - 3 categories according to motility 1) helical filaments - move by gliding 2) spirochetes - flexible walls, axial filament 3) spirilla - spiral-shaped, rigid walls, flagella All of these bacteria have a single cell arrangement. Example: cholera e. other filamentous square (Arcula) star-shaped (Stella) Mycoplasma - smallest bacteria (< 0.16 um); no cell wall, thus lacks definite shape; parasitizes animals and some plants; in humans cuases walking pneumonia
Fig. 27-2 1 µm 2 µm 5 µm (a) Spherical (cocci) (b) Rod-shaped (bacilli) (c) Spiral C. Bacterial Reproduction transformation - DNA (released by dead cells) is taken up from the surrounding environment conjugation - DNA is transferred directly from one prokaryote to another transduction - DNA is transferred from one prokaryote to another by viruses D. Nutritional and Metabolic Diversity Great diversity of modes of nutrition and metabolism. Nutrition here refers to how an organism obtains two resources for synthesizing organic compounds energy and carbon. Another aspect of metabolic diversity is whether a prokaryote uses oxygen for respiration. o o o obligate anaerobes - unable to grow in O2 obligate aerobe - must have O2 facultative anaerobe - will grow with or without O2 Nutrition/Metabolism: Table 27-1 o Heterotrophs - need an outside source of organic molecules for carbon requirement; cannot make their own food. Some are photoheterotrophs - can use light to generate ATP, but must obtain their carbon in organic form. Most are chemoheterotrophs - must have organic molecules for both energy and carbon. Used in preparation of food: pickles, sauerkraut, yogurt, buttermilk, sour cream, cheese Other: used to generate enzymes (amylase), laundry detergents, pharmaceuticals, amino acids, hormones, vitamins, antibiotics 2. parasites (pathogens) Cause disease. Examples: Salmonella - food poisoning Clostridium botulinum Clostridium tetani Pseudomonas rickettsias Neisseria gonorrhea Clostridium perfringens Staphylococcus aureus Streptococcus pyogenes Treponema pallidum Chlamydias Plant pathogens: Usually fungal or viral, but some are bacterial All bacterial plant pathogens are bacilli, most are flagellated. blight - dead and dying tissue on flowers, leaves, and stems (Erwinia amylovora) wilts - dropping leaves and stems; bacteria invades vascular system (Corynebacterium) gall - plant tumor (Argobacterium tumefaciens)
o Autotrophs - self-feeders; nonorganic source of energy; make their own food a. primitive - evolved first green sulfur and purple sulfur bacteria - do not give off oxygen; don't use H2O as the electron donor, instead they use H2 gas or H2S as electron donors; usually anaerobic; have only PI b. advanced - evolved later cyanobacteria - similar to plants; PI and PII; give off O2 (use H2O as electron donor); have chlorophyll a and blue and red pigments called phycobilins. 2. chemoautotrophs - chemosynthetic; oxidize inorganic compounds for energy Fig. 27-14 Photosynthetic cells Heterocyte 20 µm III. Domain Archaea Bacteria that inhabit extreme environments on earth. Three main groups of archaea: 1. methanogens These bacteria use H2 as electron donors to reduce CO2 to methane (CH4). Methanogens are strict anaerobes. They live in swamps and marshes and in the guts of animals. They are important decomposers. Table 27-2 ...
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This note was uploaded on 11/29/2010 for the course BUSSINESS 221242 taught by Professor Michaeldouglas during the Spring '10 term at Georgia Perimeter.
- Spring '10