Chapter 27 Prokaryotes PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Overview: They’re (Almost) Everywhere! • Most prokaryotes 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 • Prokaryotes thrive almost everywhere – Including places too acidic, too salty, too cold, or too hot for most other organisms Figure 27.1 Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Biologists are discovering – That these organisms have an astonishing genetic diversity Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Concept 27.1: 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 • Prokaryotic cells have a variety of shapes – The three most common of which are spheres (cocci), rods (bacilli), and spirals µm Figure 27.2a–c (a) Spherical (cocci) µm (b) Rod-shaped (bacilli) Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings (c) Spiral µm Cell-Surface Structures • One of the most important features of nearly all prokaryotic cells – Is their cell wall, which maintains cell shape, provides physical protection, and prevents the cell from bursting in a hypotonic environment Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Using a technique called the Gram stain – Scientists can classify many bacterial species into two groups based on cell wall composition, Grampositive 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 µm (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 • The cell wall of many prokaryotes – Is covered by a capsule, a sticky layer of polysaccharide or protein 200 nm Capsule Figure 27.4 Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Some prokaryotes have fimbriae and pili – Which allow them to stick to their substrate or other individuals in a colony Fimbriae 200 nm Figure 27.5 Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings Archaea • Archaea share certaintraits with bacteria – And other traits with eukaryotes Table 27.2 Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Some archaea – Live in extreme environments • Extreme thermophiles – Thrive in very hot environments Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Extreme halophiles – Live in high saline environments Figure 27.14 Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Methanogens – Live in swamps and marshes – Produce methane as a waste product Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Concept 27.4: Prokaryotes play crucial roles in the biosphere • Prokaryotes are so important to the biosphere that if they were to disappear – The prospects for any other life surviving would be dim Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings Chemical Recycling • Prokaryotes play a major role – In the continual recycling of chemical elements between the living and nonliving components of the environment in ecosystems Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Chemoheterotrophic prokaryotes function as decomposers – Breaking down corpses, dead vegetation, and waste products • Nitrogen-fixing prokaryotes – Add usable nitrogen to the environment Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings Symbiotic Relationships • Many prokaryotes – Live with other organisms in symbiotic relationships such as mutualism and commensalism Figure 27.15 Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Other types of prokaryotes – Live inside hosts as parasites Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Concept 27.5: Prokaryotes have both harmful and beneficial impacts on humans • Some prokaryotes are human pathogens – But many others have positive interactions with humans Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings Pathogenic Prokaryotes • Prokaryotes cause about half of all human diseases – Lyme disease is an example Figure 27.16 µm Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Pathogenic prokaryotes typically cause disease – By releasing exotoxins or endotoxins • Many pathogenic bacteria – Are potential weapons of bioterrorism Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings Prokaryotes in Research and Technology • Experiments using prokaryotes – Have led to important advances in DNA technology Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Prokaryotes are the principal agents in bioremediation – The use of organisms to remove pollutants from the environment Figure 27.17 Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Prokaryotes are 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 [...]... reproduction and horizontal gene transfer – Facilitate the evolution of prokaryotes to changing environments Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Concept 27.2: A great diversity of nutritional and metabolic adaptations have evolved in prokaryotes • Examples of all four models of nutrition are found among prokaryotes – Photoautotrophy – Chemoautotrophy – Photoheterotrophy... Education, Inc publishing as Benjamin Cummings Nitrogen Metabolism • Prokaryotes can metabolize nitrogen – In a variety of ways • In a process called nitrogen fixation – Some prokaryotes convert atmospheric nitrogen to ammonia Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings Metabolic Cooperation • Cooperation between prokaryotes – Allows them to use environmental resources they could... DNA called plasmids Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings Reproduction and Adaptation • Prokaryotes reproduce quickly by binary fission – And can divide every 1–3 hours Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Many prokaryotes form endospores – Which can remain viable in harsh conditions for centuries Endospore Figure 27.9 Copyright ©... Lessons from Molecular Systematics • Molecular systematics – Is leading to a phylogenetic classification of prokaryotes – Is allowing systematists to identify major new clades Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • A tentative phylogeny of some of the major taxa of prokaryotes based on molecular systematics Figure 27.12 Copyright © 2005 Pearson Education, Inc publishing... publishing as Benjamin Cummings Internal and Genomic Organization • Prokaryotic cells – Usually lack complex compartmentalization Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Some prokaryotes – Do have specialized membranes that perform metabolic functions 0.2 µm 1 µm Respiratory membrane Thylakoid membranes Figure 27.7a, b (a) Aerobic prokaryote Copyright © 2005 Pearson Education,... found among prokaryotes – Photoautotrophy – Chemoautotrophy – Photoheterotrophy – Chemoheterotrophy Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Major nutritional modes in prokaryotes Table 27.1 Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings Metabolic Relationships to Oxygen • Prokaryotic metabolism – Also varies with respect to oxygen Copyright ... Some prokaryotes are human pathogens – But many others have positive interactions with humans Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings Pathogenic Prokaryotes • Prokaryotes. .. many prokaryotes – Is covered by a capsule, a sticky layer of polysaccharide or protein 200 nm Capsule Figure 27.4 Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Some prokaryotes. .. and Adaptation • Prokaryotes reproduce quickly by binary fission – And can divide every 1–3 hours Copyright © 2005 Pearson Education, Inc publishing as Benjamin Cummings • Many prokaryotes form