INSTRUCTOR'S MANUAL/TEST BANK. Microbiology. With Diseases by Taxonomy. Robert W. Bauman Amarillo College. Contributors:

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1 INSTRUCTOR'S MANUAL/TEST BANK Microbiology With Diseases by Taxonomy Second Edition Robert W. Bauman Amarillo College Contributors: Lori Smith American River College Randall Harris William Carey College San Francisco Boston New York Cape Town Hong Kong London Madrid Mexico City Montreal Munich Paris Singapore Sydney Tokyo Toronto

2 Executive Editor: Leslie Berriman Senior Project Editor: Barbara Yien Editorial Assistant: Jon Duke Managing Editor: Wendy Earl Production Editor: Leslie Austin Proofreader: Martha Ghent Compositor: Cecelia G. Morales Senior Manufacturing Buyer: Stacey Weinberger Executive Marketing Manager: Lauren Harp Cover Designer: Yvo Riezebos Copyright 2007 by Pearson Education, Inc., publishing as Pearson Benjamin Cummings, San Francisco, CA All rights reserved. Printed in the United States of America. This publication is protected by Copyright and permission should be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permission(s), write to: Pearson Education, Inc., Rights and Permissions Department. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed in initial caps or all caps. ISBN : TCS

3 Contents Preface v INSTRUCTOR S MANUAL Chapter Synopses Chapter 1 A Brief History of Microbiology 1 Chapter 2 The Chemistry of Microbiology 6 Chapter 3 Cell Structure and Function 11 Chapter 4 Microscopy, Staining, and Classification 17 Chapter 5 Microbial Metabolism 22 Chapter 6 Microbial Nutrition and Growth 27 Chapter 7 Microbial Genetics 33 Chapter 8 Recombinant DNA Technology 38 Chapter 9 Controlling Microbial Growth in the Environment 42 Chapter 10 Controlling Microbial Growth in the Body: Antimicrobial Drugs 47 Chapter 11 Characterizing and Classifying Prokaryotes 51 Chapter 12 Characterizing and Classifying Eukaryotes 56 Chapter 13 Characterizing and Classifying Viruses, Viroids, and Prions 63 Chapter 14 Infection, Infectious Diseases, and Epidemiology 68 Chapter 15 Innate Immunity 73 Chapter 16 Specific Defense: Adaptive Immunity 77 Chapter 17 Immunization and Immune Testing 82 Chapter 18 Hypersensitivities, Autoimmune Diseases, and Immune Deficiencies 86 Chapter 19 Pathogenic Gram-Positive Cocci and Bacilli 91 Chapter 20 Pathogenic Gram-Negative Cocci and Bacilli 99 Chapter 21 Mycoplasmas, Rickettsias, Chlamydias, Spirochetes, and Vibrios 104 Chapter 22 Pathogenic Fungi 110 Chapter 23 Parasitic Protozoa, Helminths, and Arthropod Vectors 116 Chapter 24 Pathogenic DNA Viruses 122 Chapter 25 Pathogenic RNA Viruses 127 Chapter 26 Applied and Environmental Microbiology 134 Answers to End-of-Chapter Questions for Review 140 Answers to Critical Thinking Questions 168 Answers to Case Studies 241 iii

4 iv Instructor s Manual for Microbiology TEST BANK Chapter 1 A Brief History of Microbiology T-1 Chapter 2 The Chemistry of Microbiology T-16 Chapter 3 Cell Structure and Function T-30 Chapter 4 Microscopy, Staining, and Classification T-46 Chapter 5 Microbial Metabolism T-61 Chapter 6 Microbial Nutrition and Growth T-76 Chapter 7 Microbial Genetics T-91 Chapter 8 Recombinant DNA Technology T-106 Chapter 9 Controlling Microbial Growth in the Environment T-121 Chapter 10 Controlling Microbial Growth in the Body: Antimicrobial Drugs T-137 Chapter 11 Characterizing and Classifying Prokaryotes T-152 Chapter 12 Characterizing and Classifying Eukaryotes T-167 Chapter 13 Characterizing and Classifying Viruses, Viroids, and Prions T-181 Chapter 14 Infection, Infectious Diseases, and Epidemiology T-196 Chapter 15 Innate Immunity T-211 Chapter 16 Specific Defense: Adaptive Immunity T-225 Chapter 17 Immunization and Immune Testing T-239 Chapter 18 Hypersensitivities, Autoimmune Diseases, and Immune Deficiencies T-253 Chapter 19 Pathogenic Gram-Positive Cocci and Bacilli T-267 Chapter 20 Pathogenic Gram-Negative Cocci and Bacilli T-282 Chapter 21 Mycoplasmas, Rickettsias, Chlamydias, Spirochetes, and Vibrios T-296 Chapter 22 Pathogenic Fungi T-310 Chapter 23 Parasitic Protozoa, Helminths, and Arthropod Vectors T-324 Chapter 24 Pathogenic DNA Viruses T-338 Chapter 25 Pathogenic RNA Viruses T-352 Chapter 26 Applied and Environmental Microbiology T-366

5 Preface This volume contains the Instructor s Manual and Test Bank accompanying Microbiology, 2nd ed. by Robert Bauman. The Instructor s Manual consists of the following resources: Detailed chapter synopsis for each chapter of the text Answers to end-of-chapter Questions for Review Answers to in-text and end-of-chapter Critical Thinking Questions Answers to in-text Case Studies The Test Bank consists of approximately 1800 multiple-choice, matching, true/false, fill-in-the-blank, short-answer, and essay questions. Below is a list of additional print and media resources available to you as an adopter of Microbiology. Contact your local Benjamin Cummings representative if you would like to order any additional supplements. To locate the representative nearest you, visit or call ADDITIONAL INSTRUCTOR RESOURCES Media Manager Instructor CD-ROMs This powerful set of CD-ROMs includes a powerful, extensive suite of resources for classroom presentation, including: JPEG and PowerPoint files of every illustration, photograph, and table from the text. Figures are shown in two formats: (1) with labels and leaders and (2) without labels and leaders. Prepared PowerPoint lecture outlines for each chapter Layered, step-by-step, customizable PowerPoint slides for selected key figures The ability to edit labels and leaders 30 robust, interactive Flash animations on selected key topics in microbiology 25 QuickTime live-action videos of microorganisms Active Lecture Questions designed for use with personal response clicker systems An editable electronic Word file of the Test Bank A link to the online E-book for Microbiology, 2nd ed. Instructor s Visual Guide This printed supplement contains quick-reference thumbnail views of all of the assets on the Media Manager Instructor CD-ROMs. v

6 vi Instructor s Manual for Microbiology Full-Color Transparency Acetates Contains over 650 full-color transparency acetates, including every illustration and table from the text. Biological Agents of Disease/HIV Slide Set for Microbiology Contains 100 clinical photos of microorganisms and pathologies, all from sources other than the text. Computerized Test Bank This cross-platform, easy-to-use testing program allows instructors to view and edit electronic questions from the Test Bank, create multiple tests, and print them in a variety of formats. Course Management Options CourseCompass (Student Access Kit ) CourseCompass is a nationally hosted online course management system that offers pre-loaded, book-specific content including testing and assessment, weblinks, illustrations, and photos. Visit for a demonstration and more information about CourseCompass. Blackboard and WebCT Pre-loaded book-specific content and test items files accompanying the text are available in open-access Blackboard and open-access WebCT formats. Contact your local Benjamin Cummings sales representative for more information. UPDATES TO THE SECOND EDITION The second edition of Microbiology has been extensively revised to present the most up-to-date coverage possible. Below is a list of new and updated content, boxes, figures, and photos you ll find in this edition. Chapter 1 New New Frontiers box: The Challenge of Emerging and Re-Emerging Diseases Chapter 2 Coverage of newly discovered 21st and 22nd amino acids has been added. New Highlight box: Architecture-Preserving Bacteria Chapter 3 Coverage of endospores has been added. Discussion of eukaryotic flagella and cilia has been reorganized to emphasize that these structures are internal to the cytoplasmic membrane. Coverage has been added of new discoveries concerning cell structure and function. Two examples follow: 1. Some prokaryotic cytoskeletons are contractile, allowing nonflagellated cells that possess them to be motile. 2. The cytoplasmic membrane is not uniform and fluid, but rather contains regions with unique lipid and protein molecules called lipid rafts.

7 Preface vii Chapter 4 New Applying Molecular Techniques box: Studying Biofilms on Stromatolites Chapter 6 Presents new hyperthermophile record holder, Geogemma, formerly called strain 121 New Applying Molecular Techniques box: Hydrogen-Loving Microbes in Yellowstone s Hot Springs New New Frontiers box: A Nuclear-Waste-Eating Microbe? Chapter 7 Text has been updated and rewritten to better distinguish bacterial genetics and eukaryotic genetics. Includes new research indicating that sigma factor of RNA polymerase does not necessarily disengage during transcription Covers newly discovered codons for 21st and 22nd amino acids Covers actions of topoisomerase and gyrase Artwork has been updated to reflect changes in our understanding of molecular biology. For example, where possible, enzyme shapes are based upon actual 3D profiles as revealed by X-ray crystallography. Coverage has been added of quorum sensing as it relates to genetic control in infection. Coverage has been added of regulation of genetic expression antisense RNA, RNA interference (RNAi), riboswitches. The overwhelming nature of horizontal gene transfer among prokaryotes is discussed. New Applying Molecular Techniques box: Could Studying a Bacterial Genome Result in New Treatments for Acne? New Applying Molecular Techniques box: RNA Interference Chapter 8 Added coverage of using recombinant DNA technology to produce antisense nucleic acid molecules Added coverage of DNA microarrays Added coverage of new recombinant crops, including potato-blight resistant potatoes Three new figures New Applying Molecular Techniques box: Unlocking the Secrets of Candida albicans New Applying Molecular Techniques box: Could Bacteria Help Decaffeinate Coffee? Chapter 10 Added discussion of use of RNA interference (RNAi) and antisense nucleic acid as antimicrobial therapy Figure 10.3 has been revised Updated and revised tables of antimicrobials New Applying Molecular Techniques box: Monoclonal Antibodies to the Rescue?

8 viii Instructor s Manual for Microbiology Chapter 11 New photos of bacteria and Archaea Coverage of new hyperthermophile record holder Geogemma ( strain 121 ) New Highlight box: From Cyanobacteria to Bats to Brain Disease? New Highlight box: Streptomyces and the European Beewolf Chapter 12 Updated algal, fungal, protozoan, water mold, and slime mold taxonomy New photos for fungal hyphae and for dimorphic fungi New fungal life cycle artwork to more clearly delineate nuclear states Clarified cyst-trophozoite conversion for intestinal protozoa Chapter 13 Updated viral nomenclature to correspond to changes approved by the International Committee on Taxonomy of Viruses; for example, herpes simplex viruses are officially known as human herpesvirus 1 and 2 New TEMs of viruses New New Frontiers box: The Threat of Avian Influenza Chapter 14 Incidence and prevalence figure redrawn to reflect actual AIDS data in the U.S. Chapter 15 Revised to clarify the structures and processes of innate immunity, including coverage of toll-like receptors, antimicrobial peptides, neutrophil extracellular traps (NETs) Includes latest discoveries in iron usage among pathogenic bacteria Clarified artwork and discussion of pathways of complement activation Clarified that cells and fluid move from venules during dilation and inflammation Chapter 16 Updated coverage of adaptive immunity to reflect new discoveries and enhance accuracy and clarity; for example, added coverage of direct killing of bacteria by antibodies via ozone production New Applying Molecular Techniques box: How do Viruses Thwart the Immune System? Chapter 17 Updated vaccination schedules and incidence of preventable diseases in U.S. Chapter 19 New Highlight box: Botulism in Alaska New Microbe-at-a-Glance features on Staphylococcus aureus and Clostridium botulinum Chapter 20 Added coverage of Burkholderia, which is a major pathogen in cystic fibrosis patients and can be an important agent in the bioremediation of many long-lived organic contaminants

9 Preface ix New Highlight box: The Mystery of Tularemia on Martha s Vineyard New Microbe-at-a-Glance features on Neisseria gonorrhoea and Escherichia coli Chapter 21 New Microbe-at-a-Glance features on Treponema pallidum pallidum and Helicobacter pylori Chapter 22 New Microbe-at-a-Glance features on Aspergillus and Giardia intestinalis Chapter 23 Updated treatment and prevention of parasitic diseases, including use of the antimalarial drug artemisinin Vectors in life cycle drawings are now life size. Updated the malaria map New Highlight box: Baghdad Boil New Highlight box: Snail Fever Returns to China New Microbe-at-a-Glance features on Giardia intestinalis and Plasmodium falciparum Chapter 24 Updated incidence, treatment, and prevention for DNA viral diseases New Highlight box: Monkeypox New Microbe-at-a-Glance features on smallpox and adenovirus Chapter 25 Updated coverage of SARS, West Nile encephalitis, rotaviral diarrhea, AIDS, and Marburg hemorrhagic fever Updated incidence, treatment, and prevention for RNA viral diseases New Applying Molecular Techniques box: Sequencing the SARS Virus New Highlight box: AIDS and Tuberculosis New Microbe-at-a-Glance features on HIV and influenzavirus Chapter 26 Added anammox reactions to nitrogen cycle FIVE TIPS FOR MAXIMIZING RESOURCES AVAILABLE WITH YOUR TEXTBOOK 1. Assign animations to your students. Thirty interactive animations are available to your students on both the website at and on The Microbiology Place CD-ROM included with each new copy of the textbook. You will find in-text references to the animations in the summaries that appear at the end of each chapter, as well as throughout the text. Assess your students understanding of the animations by having them work through the animation quizzes on the website. A list of animation topics follows, along with their corresponding chapter references:

10 x Instructor s Manual for Microbiology Animation Chapter Bacterial Motility 3 Membrane Transport 3 Microscopy 4 Dichotomous Keys 4 Metabolic Pathways (Overview) 5 Enzyme-Substrate Interactions 5 Glycolysis 5 Krebs Cycle 5 Electron Transport Chains and Chemiosmosis 5 Photosynthesis 5 DNA Replication 7 Transcription 7 Translation 7 Operons 7 Mutations and DNA Repair 7 Horizontal Gene Transfer 7 Bacterial Conjugation 7 Transposons 7 Polymerase Chain Reaction 8 Bacterial Growth 11 Viral Replication 13 Prion Reproduction 13 Epidemiology 14 Host Defenses 15 Phagocytosis 15 The Complement System 115 Inflammation 15 Humoral Immunity 16 Cell-Mediated Immunity 16 Antigen Processing and Presentation Assign MicroPrep Pre-Tests to your students. On the first page of each chapter in the textbook, there is a note that directs students to a multiple-choice Pre-Test for that chapter. The Pre-Tests are available both online at as well as on The Microbiology Place CD-ROM included with each new copy of the textbook. The Pre-Tests are designed to be taken before the student reads the chapter in order to (1) test the students knowledge of material covered in previous chapters, and (2) test the students preconceptions of the topics covered in the chapters on hand. By taking the Pre- Tests, students are alerted to topics that they may wish to review prior to reading the assigned chapter. 3. Encourage your students to use The Microbiology Place website and CD-ROM. They ll find extensive study aids on The Microbiology Place, including: Objectives to help them focus on the most important concepts and topics to master in each chapter Pre-Tests to assess prior knowledge and/or pre-conceptions of topics relevant to the chapter at hand Practice Tests to assess mastery of chapter topics Microbe Reviews feature full-color micrographs from the textbook and allow you to review the characteristics of individual microbes (website only)

11 Preface xi Web Links consisting of recommended links to microbiology information, micrographs, and video clips for further exploration of topics in each chapter Animations to master the toughest topics in microbiology, via interactive, animated tutorials (Quizzes on the animations can be found on the website.) Flashcards to help students review key terms and concepts from the text Videos featuring live-action videos of microorganisms, illustrating microbial structures and motility Careers providing useful information about working in a microbiologyrelated field; basic research, applied research, and health professions are covered Research News pointing students to resources on the web focusing on new and/or ongoing research in microbiology-related fields Research Navigator provides access to a powerful online database of trusted, reliable science publications (website only) E-Book provides the complete text of Microbiology, 2nd ed. in online electronic format (website only) 4. Order your textbooks packaged with access to The Tutor Center. Microbiology, 2nd edition is supported by The Tutor Center, which offers high quality, oneon-one tutoring to students. Contact your local Benjamin Cummings representative for more information, or visit: 5. Make use of the Appendix included at the back of the text. You ll find many additional resources in the Appendix, which contains: Appendix A: Metabolic Pathways Five detailed color illustrations of Glycolysis (Embden-Meyerhof pathway); Pentose-Phosphate pathway; Entner-Doudoroff pathway; Krebs Cycle; and the Calvin-Benson cycle Appendix B: Some Mathematical Considerations in Microbiology Covering scientific notation, logarithms, and generation time Appendix C: An abridged version of Bergey s Manual of Systematic Bacteriology (Springer: New York) includes updates through May 2005 Appendix D: Major Microbial Agents of Disease by Body System Affected Appendix E: Answers to End-of-Chapter Questions You ll also find a pronunciation key of selected microorganisms on the front and back covers of the textbook. SEND US YOUR FEEDBACK We hope that you find the Instructor s Manual and Test Bank useful, and we welcome your comments and feedback! Please write to us at the following address: Robert Bauman c/o Applied Sciences, Benjamin Cummings 1301 Sansome St. San Francisco, CA 94111

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15 A Brief History of Microbiology 1 SYNOPSIS The Early Years of Microbiology (pp. 2 7) The early years of microbiology brought the first observations of microbial life and the initial efforts to organize them into logical classifications. What Does Life Really Look Like? Antoni van Leeuwenhoek ( ), a Dutch tailor, made the first simple microscope in order to examine the quality of cloth. The device was little more than a magnifying glass with screws for manipulating the specimen, but it allowed him to begin the first rigorous examination and documentation of the microbial world. He reported the existence of protozoa in 1674 and of bacteria in By the end of the 19th century, Leeuwenhoek s beasties were called microorganisms. Today they are also known as microbes. How Can Microbes Be Classified? During the 18th century, Carolus Linnaeus ( ), a Swedish botanist, developed a taxonomic system for naming plants and animals and grouping similar organisms together. Biologists still use a modification of Linnaeus taxonomy today. All living organisms can be classified as either eukaryotic or prokaryotic. Eukaryotes are organisms whose cells contain a nucleus composed of genetic material surrounded by a distinct membrane. Prokaryotes are unicellular microbes that lack a true nucleus. Within these categories, microorganisms are further classified as follows: Fungi are relatively large microscopic eukaryotes and include molds and yeasts. These organisms obtain their food from other organisms and have cell walls. Protozoa are single-celled eukaryotes that are similar to animals in their nutritional needs and cellular structure. Most are capable of locomotion, and some cause disease. Algae are plant-like eukaryotes that are photosynthetic; that is, they make their own food from carbon dioxide and water using energy from sunlight. Bacteria are unicellular prokaryotes whose cell walls are composed of peptidoglycan (though some bacteria lack cell walls). Most are beneficial, but some cause disease. Archaea are single-celled prokaryotes whose cell walls lack peptidoglycan and instead are composed of other polymers. Viruses are microorganisms so small that they were hidden from microbiologists until the invention of the electron microscope in All are acellular obligatory parasites. Microbiologists also study parasitic worms, which range in size from microscopic forms to adult tapeworms several meters in length. 1

16 2 Instructor s Manual for Microbiology The Golden Age of Microbiology (pp. 7 18) During what is now sometimes called the Golden Age of Microbiology, from the late 19th to the early 20th century, microbiologists competed to be the first to answer several questions about the nature of microbial life. Is Spontaneous Generation of Microbial Life Possible? The theory of spontaneous generation (or abiogenesis) proposes that living organisms can arise from nonliving matter. It was proposed by Aristotle ( BC) and was widely accepted for almost 2000 years, until experiments by Francesco Redi ( ) challenged it. In the 18th century, British scientist John T. Needham ( ) conducted experiments suggesting that perhaps spontaneous generation of microscopic life was indeed possible, but in 1799, experiments by Italian scientist Lazzaro Spallanzani ( ) reported results that contradicted Needham s findings. The debate continued until experiments by French scientist Louis Pasteur ( ) using swan-necked flasks that remained free of microbes disproved the theory definitively. The debate over spontaneous generation led in part to the development of a generalized scientific method by which questions are answered through observations of the outcomes of carefully controlled experiments. It consists of four steps: 1. A group of observations leads a scientist to ask a question about some phenomenon. 2. The scientist generates a hypothesis a potential answer to the question. 3. The scientist designs and conducts an experiment to test the hypothesis. 4. Based on the observed results of the experiment, the scientist either accepts, rejects, or modifies the hypothesis. What Causes Fermentation? The mid-19th century also saw the birth of the field of industrial microbiology (or biotechnology), in which microbes are intentionally manipulated to manufacture products. Pasteur s investigations into the cause of fermentation led to the discovery that yeast can grow with or without oxygen, and that bacteria ferment grape juice to produce acids, whereas yeast cells ferment grape juice to produce alcohol. These discoveries suggested a method to prevent the spoilage of wine by heating the grape juice just enough to kill contaminating bacteria, so that it could then be inoculated with yeast. Pasteurization, the use of heat to kill pathogens and reduce the number of spoilage microorganisms in food and beverages, is an industrial application widely used today. In 1897, experiments by the German scientist Eduard Buchner ( ) demonstrated the presence of enzymes, cell-produced proteins that promote chemical reactions such as fermentation. His work began the field of biochemistry and the study of metabolism, a term that refers to the sum of all chemical reactions in an organism. What Causes Disease? Prior to the 1800s, disease was attributed to various factors such as evil spirits, sin, imbalances in body fluids, and foul vapors. Pasteur s discovery that bacteria are responsible for spoiling wine led to his hypothesis in 1857 that microorganisms are also responsible for diseases, an idea that came to be known as the germ theory of disease. Microorganisms that cause specific diseases are caused pathogens. Today we know that diseases are also caused by genetics, environmental toxins, and allergic reactions; thus, the germ theory applies only to infectious disease.

17 Chapter 1 A Brief History of Microbiology 3 Investigations into etiology, the study of the causation of disease, were dominated by German physician Robert Koch ( ). Koch initiated careful microbiological laboratory techniques in his search for disease agents, such as the bacterium responsible for anthrax. He and his colleagues were responsible for developing techniques to isolate bacteria, stain cells, estimate population size, sterilize growth media, and transfer bacteria between media. They also achieved the first photomicrograph of bacteria. But one of Koch s greatest achievements was the elaboration, in his publications on tuberculosis, of a set of steps that must be taken to prove the cause of any infectious disease. These four steps are now known as Koch s postulates: 1. The suspected causative agent must be found in every case of the disease and be absent from healthy hosts. 2. The agent must be isolated and grown outside the host. 3. When the agent is introduced to a healthy, susceptible host, the host must get the disease. 4. The same agent must be reisolated from the diseased experimental host. In 1884, Danish scientist Christian Gram ( ) developed a staining technique involving application of a series of dyes that leave some microbes purple and others pink. The Gram stain is still the most widely used staining technique; it distinguishes Gram-positive from Gram-negative bacteria and reflects differences in composition of the bacterial cell wall. How Can We Prevent Infection and Disease? In the mid-19th century, modern principles of hygiene, such as those involving sewage and water treatment, personal cleanliness, and pest control, were not widely practiced. Medical facilities and personnel lacked adequate cleanliness, and nosocomial infections, those acquired in a health care facility, were rampant. In approximately 1848, Viennese physician Ignaz Semmelweis ( ) noticed that women whose births were attended by medical students died at a rate 20 times higher than those whose births were attended by midwives in an adjoining wing of the same hospital. He hypothesized that cadaver particles from the hands of the medical students caused puerperal fever, and required medical students to wash their hands in chlorinated lime water before attending births. Mortality from puerperal fever in the subsequent year dropped precipitously. A few years later, English physician Joseph Lister ( ) advanced the idea of antisepsis in health care settings, reducing deaths among his patients by two-thirds with the use of phenol. Florence Nightingale ( ), the founder of modern nursing, introduced antiseptic techniques that saved the lives of innumerable soldiers during the Crimean War of In 1854, observations by the English physician John Snow ( ) mapping the occurrence of cholera cases in London led to the foundation of two branches of microbiology: infection control and epidemiology, the study of the occurrence, distribution, and spread of disease in humans. The field of immunology, the study of the body s specific defenses against pathogens, began with the experiments of English physician Edward Jenner ( ), who showed that vaccination with pus collected from cowpox lesions prevented smallpox. Pasteur later capitalized on Jenner s work to develop successful vaccines against fowl cholera, anthrax, and rabies. The field of chemotherapy, a branch of medical microbiology in which chemicals are studied for their potential to destroy pathogenic microorganisms, began when German microbiologist Paul Ehrlich ( ) began to search for a magic

18 4 Instructor s Manual for Microbiology bullet that could kill microorganisms but remain nontoxic to humans. By 1908, he had discovered chemicals effective against the agents that cause sleeping sickness and syphilis. The Modern Age of Microbiology (pp ) Since the early 20th century, microbiologists have worked to answer new questions in new fields of science. What Are the Basic Chemical Reactions of Life? Biochemistry is the study of metabolism. It began with Pasteur s work on fermentation and Buchner s discovery of enzymes, but was greatly advanced by the proposition of microbiologists Albert Kluyver ( ) and C. B. van Niel ( ) that biochemical reactions are shared by all living things, are few in number, and involve the transfer of electrons and hydrogen ions. In adopting this view, scientists could begin to use microbes as model systems to answer questions about metabolism in other organisms. Today, biochemical research has many practical applications, including: the design of herbicides and pesticides; the diagnosis of illness; the treatment of metabolic diseases; and the design of drugs to treat various disorders. How Do Genes Work? Microbial genetics is the study of inheritance in microorganisms. Throughout the 20th century, researchers working with microbes made significant advances in our understanding of how genes work. For example, they established that a gene s activity is related to the function of the specific protein coded by that gene, and they determined the exact way in which genetic information is translated into a protein. Molecular biology combines aspects of biochemistry, cell biology, and genetics to explain cell function at the molecular level. It is particularly concerned with genome sequencing. Genetic engineering involves the manipulation of genes in microbes, plants, and animals for practical applications, such as the development of pest-resistant crops and the treatment of disease. Gene therapy is the use of recombinant DNA (DNA composed of genes from more than one organism) to insert a missing gene or repair a defective gene in human cells. What Roles Do Microorganisms Play in the Environment? Environmental microbiology studies the role microorganisms play in their natural environment. Microbial communities play an essential role, for example, in the decay of dead organisms and the recycling of chemicals such as carbon, nitrogen, and sulfur. Environmental microbiologists study the microbes and chemical reactions involved in such biodegradation, as well as the effects of community-based measures to limit the abundance of pathogenic microbes in the environment, such as sewage treatment, water purification, and sanitation measures. How Do We Defend Against Disease? Although the work of Jenner and Pasteur marked the birth of the field of immunology, the discovery of chemicals in the blood that are active against specific pathogens advanced the field considerably. Serology is the study of blood serum, the liquid that remains after blood coagulates, and that carries disease-fighting chemicals. Serologic studies showed that the body can defend itself against a remarkable range

19 Chapter 1 A Brief History of Microbiology 5 of diseases. Nevertheless, medical intervention is often necessary, and the 20th century saw tremendous advances in chemotherapy, including the discovery of penicillin in 1929 and sulfa drugs in 1935, both of which are still first-line antimicrobial drugs today. What Will the Future Hold? Among the questions microbiologists are working to answer today are the following: What prevents certain life forms from being grown in the laboratory? Can microorganisms be used in ultraminiature technologies such as computer circuit boards? How can an understanding of microbial communities help us understand communities of larger organisms? What can we do at a genetic level to defend against pathogenic microorganisms? How can we reduce the threat of new and re-emerging infectious diseases?