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Chapter 27 Prokaryotes Bugs • They’re (Almost) Everywhere! • Most are microscopic – But what they lack in size they more than make up for in numbers • The number of prokaryotes in a single handful of fertile soil – Is greater than the number of people who have ever lived Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Metabolically diverse • thrive almost everywhere – Includes too acidic, too salty, too cold, or too hot areas Figure 27.1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotes • Structural, functional, and genetic adaptations contribute to prokaryotic success • Most prokaryotes are unicellular – Although some species form colonies Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotes • Most unicellular, some in colonys – three most common shapes: spheres (cocci), rods (bacilli), and spirals (spirochetes) 1 m Figure 27.2a–c (a) Spherical (cocci) 2 m (b) Rod-shaped (bacilli) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 5 m (c) Spiral Cell-Surface Structures cell wall, • maintains cell shape, • provides physical protection, • prevents the cell from bursting in a hypotonic environment Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gram stain classifies many bacterial species into two groups based on cell wall composition, Gram-positive and Gram-negative Lipopolysaccharide Cell wall Peptidoglycan layer Cell wall Outer membrane Peptidoglycan layer Plasma membrane Plasma membrane Protein Protein Grampositive bacteria Gramnegative bacteria 20 m (a) Gram-positive. Gram-positive bacteria have a cell wall with a large amount of peptidoglycan that traps the violet dye in the cytoplasm. The alcohol rinse does not remove the violet dye, which masks the added red dye. Figure 27.3a, b Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) Gram-negative. Gram-negative bacteria have less peptidoglycan, and it is located in a layer between the plasma membrane and an outer membrane. The violet dye is easily rinsed from the cytoplasm, and the cell appears pink or red after the red dye is added. Cell wall • capsule, sticky layer of polysaccharide or protein – To avoid phagocytosis, attach to host cells 200 nm Capsule Figure 27.4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotes • fimbriae and pili – to stick to substrate or individuals in a colony Fimbriae 200 nm Figure 27.5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Motility • bacteria propel themselves by flagella – structurally and functionally different from eukaryotic flagella Flagellum Filament 50 nm Cell wall Hook Basal apparatus Figure 27.6 Plasma membrane Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic cells – Usually lack complex compartmentalization Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some…. – Do have specialized membranes that perform metabolic functions 0.2 m 1 m Respiratory membrane Thylakoid membranes Figure 27.7a, b (a) Aerobic prokaryote Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (b) Photosynthetic prokaryote Genome – ring of DNA not surrounded by membrane, located in a nucleoid region Chromosome Figure 27.8 1 m Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bacteria • Some species – have smaller rings of DNA called plasmids • Plasmids can carry toxin or antibiotic resistance genes – Prokaryotes reproduce by binary fission • And can divide every 1–3 hours (20 mins for E. coli, optimal conditions) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endospores – Found in many soil bacteria, act like seeds • Cause botulism in poorly cooked foods – can remain viable in harsh conditions for centuries Endospore 0.3 m Figure 27.9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bacillus anthracis (anthrax) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotic metabolism • great diversity of nutritional and metabolic adaptations, can metabolize almost anything you can think of! • Four models of nutrition – Photoautotrophy – Chemoautotrophy – Photoheterotrophy – Chemoheterotrophy Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nutrition Table 27.1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Metabolic Relationships to Oxygen • Prokaryotic metabolism – Also varies with respect to oxygen – Why? Evolution of course! Cyanobacteria Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Metabolic Relationships to Oxygen • Obligate aerobes – Require oxygen • Facultative anaerobes – Can survive with or without oxygen • Obligate anaerobes – Are poisoned by oxygen Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nitrogen Metabolism • Prokaryotes can metabolize nitrogen • Nitrogen fixation – Some prokaryotes convert atmospheric nitrogen to ammonia Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cooperation in bacteria • In the cyanobacterium Anabaena – Photosynthetic cells and nitrogen-fixing cells exchange metabolic products Photosynthetic cells Heterocyst 20 m Figure 27.10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cooperation • In some prokaryotic species 1 m – Metabolic cooperation occurs in surfacecoating colonies called biofilms Figure 27.11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Center for Biofilm Engineering, MSU A Friendly Guide to Biofilm Basics & the CBE 1. What is biofilm? You may not be familiar with the term "biofilm," but you have certainly encountered biofilm on a regular basis. The plaque that forms on your teeth and causes tooth decay is a type of bacterial biofilm. The "gunk" that clogs your drains is also biofilm. If you have ever walked in a stream or river, you may have slipped on the biofilm-coated rocks. Biofilm forms when bacteria adhere to surfaces in aqueous environments and begin to excrete a slimy, glue-like substance that can anchor them to all kinds of material – such as metals, plastics, soil particles, medical implant materials, and tissue. A biofilm can be formed by a single bacterial species, but more often biofilms consist of many species of bacteria, as well as fungi, algae, protozoa, debris and corrosion products. Essentially, biofilm may form on any surface exposed to bacteria and some amount of water. Once anchored to a surface, biofilm microorganisms carry out a variety of detrimental or beneficial reactions (by human standards), depending on the surrounding environmental conditions. What is the industrial significance of biofilm? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Archaea – can live in extreme environments • Eg. Extreme halophiles – Live in high saline environments Figure 27.14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotes • play a major role in chemical recycling • Chemoheterotrophic prokaryotes function as decomposers • Nitrogen-fixing prokaryotes – Add usable nitrogen to the environment Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbiotic Relationships – Many live with other organisms in symbiotic relationships (mutualism and commensalism) Figure 27.15 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pathogenic Prokaryotes • Prokaryotes cause about half of all human diseases – Eg. Lyme disease Figure 27.16 5 µm Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Diseases • Pathogenic prokaryotes typically cause disease – By releasing exotoxins or endotoxins • Many pathogenic bacteria – Are potential weapons of bioterrorism – Anthrax, plague, Tularemia (rabbit fever) – Toxins: botulism Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Caution About a Bioterror Attack on the U.S. Milk Supply June 2005 STANFORD GRADUATE SCHOOL OF BUSINESS — A mere 4 grams of botulinum toxin dropped into a milk production facility could cause serious illness and even death for 400,000 people in the United States. Investments that would cost the public only 1 cent more per half-gallon of milk could prevent this nightmare scenario, according to Lawrence M. Wein of the Stanford Graduate School of Business. Wein, the Paul E. Holden Professor of Management Science, has been conducting a series of studies on the effects of various potential terrorist activities in United States. Not only milk, but soft drinks, fruit and vegetable juices, processed tomato products, and even grains—anything that goes through large-scale storage and production and rapid distribution—could be at risk for such an attack, with catastrophic consequences for the American public, Wein says in his most recent study, conducted with Yifan Liu, a PhD candidate at the Institute for Computational and Mathematical Engineering at Stanford University. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bioremediation – The use of organisms to remove pollutants from the environment Figure 27.17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Also • major tools in: – Mining – The synthesis of vitamins – Production of antibiotics, hormones, and other products Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Antibiotics produced by Bacteria • Antibiotic Bacterial Species • Tetracycline Streptomyces remosus • Streptomycin Streptomyces griseus • Cyclohexamide Streptomyces griseus • Neomycin Streptomyces frodiae • Cycloserine Streptomyces orchidaceus • Erythromycin Streptomyces erythreus • Kanamycin Streptomyces kanamyceticus • Lincomycin Streptomyces lincolnensis • Nystatin Streptomyces noursei • Polymyxin B Bacillus polymyxa • Bacitracin Bacillus licheniformis • And streptokinase – clot busting drug from Streptococcus Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings