Prescott's Microbiology Eleventh Edition PDF

eleventh edition Prescott’s Microbiology Joanne M. Willey HOFSTRA UNIVERSITY Kathleen M. Sandman Dorothy H. Wood...

eleventh edition Prescott’s Microbiology Joanne M. Willey HOFSTRA UNIVERSITY Kathleen M. Sandman Dorothy H. Wood DURHAM TECHNICAL COMMUNITY COLLEGE wil11886_fm_i-xxiv.indd 1 23/10/18 2:12 pm  PRESCOTT’S MICROBIOLOGY, ELEVENTH EDITION Published by McGraw-Hill Education, 2 Penn Plaza, New York, NY 10121. Copyright © 2020 by McGraw-Hill Education. All rights reserved. Printed in the United States of America. Previous editions © 2017, 2014, and 2011. No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written consent of McGraw-Hill Education, including, but not limited to, in any network or other electronic storage or transmission, or broadcast for distance learning. Some ancillaries, including electronic and print components, may not be available to customers outside the United States. This book is printed on acid-free paper. 1 2 3 4 5 6 7 8 9 LWI 22 21 20 19 ISBN 978-1-260-21188-7 MHID 1-260-21188-6 Portfolio Manager: Marija Magner Product Developer: Darlene M. Schueller Marketing Manager: Valerie L. Kramer Content Project Managers: Laura Bies, Tammy Juran & Sandra Schnee Buyer: Sandy Ludovissy Design: Matt Backhaus Content Licensing Specialists: Shawntel Schmitt & Beth Cray Cover Image: Source: Photo by De Wood, digital colorization by Chris Pooley, USDA-ARS Compositor: MPS Limited All credits appearing on page or at the end of the book are considered to be an extension of the copyright page. Library of Congress Cataloging-in-Publication Data Willey, Joanne M., author. Prescott’s microbiology / Joanne M. Willey, Hofstra University, Kathleen M. Sandman, Dorothy H. Wood, Durham Technical Community College. Microbiology Eleventh edition. | New York, NY : McGraw-Hill Education, | Includes bibliographical references and index. LCCN 2018026319 | ISBN 9781260211887 (student edition) LCSH: Microbiology—Textbooks. LCC QR41.2.P74 2020 | DDC 579—dc23 The Internet addresses listed in the text were accurate at the time of publication. The inclusion of a website does not indicate an endorsement by the authors or McGraw-Hill Education, and McGraw-Hill Education does not guarantee the accuracy of the information presented at these sites. mheducation.com/highered wil11886_fm_i-xxiv.indd 2 23/10/18 2:12 pm  Brief Contents About the Authors iv 25 Fungi 579 26 Viruses 594 Part One Introduction to Microbiology 1 The Evolution of Microorganisms and Part Six Ecology and Symbiosis Microbiology 1 27 Microbial Interactions 619 2 Microscopy 20 28 Biogeochemical Cycling and Global Climate 3 Bacterial Cell Structure 40 Change 632 4 Archaeal Cell Structure 77 29 Methods in Microbial Ecology 646 5 Eukaryotic Cell Structure 87 30 Microorganisms in Marine and Freshwater 6 Viruses and Other Acellular Infectious Agents 106 Ecosystems 658 31 Microorganisms in Terrestrial Ecosystems 675 Part Two Microbial Nutrition, Growth, and Control Part Seven Pathogenicity and Host Response 7 Bacterial and Archaeal Growth 128 32 Innate Host Resistance 693 8 Control of Microorganisms in the Environment 170 33 Adaptive Immunity 719 9 Antimicrobial Chemotherapy 187 34 The Microbe-Human Ecosystem 752 35 Infection and Pathogenicity 770 Part Three Microbial Metabolism 10 Introduction to Metabolism 209 Part Eight Microbial Diseases, Detection, and 11 Catabolism: Energy Release and Conservation 228 Their Control 12 Anabolism: The Use of Energy in Biosynthesis 265 36 Epidemiology and Public Health Microbiology 786 37 Clinical Microbiology and Immunology 806 38 Human Diseases Caused by Viruses and Prions 825 Part Four Microbial Molecular Biology and Genetics 39 Human Diseases Caused by Bacteria 857 13 Bacterial Genome Replication and Expression 288 40 Human Diseases Caused by Fungi and Protists 900 14 Regulation of Bacterial Cellular Processes 326 15 Eukaryotic and Archaeal Genome Replication and Expression 355 Part Nine Applied Microbiology 16 Mechanisms of Genetic Variation 375 41 Microbiology of Food 925 17 Microbial DNA Technologies 405 42 Biotechnology and Industrial Microbiology 944 18 Microbial Genomics 425 43 Applied Environmental Microbiology 960 Appendix 1 A Review of the Chemistry of Biological Molecules A-1 Part Five The Diversity of the Microbial World Appendix 2 Common Metabolic Pathways A-9 19 Microbial Taxonomy and the Evolution of Diversity 447 20 Archaea 466 Appendix 3 Microorganism Pronunciation Guide A-17 21 Nonproteobacterial Gram-Negative Bacteria 484 Glossary G-1 22 Proteobacteria 504 Index I-1 23 Gram-Positive Bacteria 537 24 Protists 559 iii wil11886_fm_i-xxiv.indd 3 23/10/18 2:12 pm  About the Authors Courtesy of Joanne Willey Courtesy of Adele Anderson Courtesy of Dorothy Wood Joanne M. Willey has been a Kathleen M. Sandman received her Dorothy H. Wood has taught professor at Hofstra University on Long B.A. in Biology from La Salle University microbiology and general biology at Island, New York, since 1993, where she is and her Ph.D. in Cellular and Developmental Durham Technical Community College in the Leo A. Guthart Professor of Biology from Harvard University. She was North Carolina since 2004. Dr. Wood Biomedical Science and Chair of the inspired to a career in science by her older received her B.A. in Biology from Rhode Department of Science Education at the brother’s experience as an organic chemist Island College where her love of microbes Donald and Barbara Zucker School of and by the developing technology in began, nurtured by Dr. Charles Owens. Medicine at Hofstra/Northwell. Dr. Willey recombinant DNA in the 1970s. Her She earned her Ph.D. in Cell and received her B.A. in Biology from the graduate work used a transposable element Molecular Pathology from the University University of Pennsylvania, where her as a mutagen in Bacillus subtilis to study of North Carolina at Chapel Hill, focusing interest in microbiology began with work gene expression during endospore formation. on pancreatic damage caused by on cyanobacterial growth in eutrophic She continued in the genetics of Gram- antimicrobial drugs, and investigated streams. She earned her Ph.D. in positive bacteria with a postdoctoral year alternative therapies based on receptor biological oceanography (specializing studying Bacillus thuringiensis at the binding by novel compounds. After three in marine microbiology) from the University of Cambridge in the United years as Assistant Professor at NC Central Massachusetts Institute of Technology– Kingdom. Another postdoctoral opportunity University, Dr. Wood made the move to Woods Hole Oceanographic Institution at The Ohio State University provided an the NC Community College System to Joint Program in 1987. She then went to introduction to the emerging field of focus her attention on her primary interest Harvard University, where she spent her archaeal molecular biology, where of teaching. Throughout her career she has postdoctoral fellowship studying the Dr. Sandman discovered archaeal histones developed several courses, including filamentous soil bacterium Streptomyces and continued research in the structural graduate bacteriology, pathophysiology, coelicolor. Dr. Willey has coauthored a biology of archaeal chromatin for about and biotechnology. She serves as a visiting number of publications that focus on its 20 years. She served the National Science scholar at Duke University where she is a complex developmental cycle. She is an Foundation as a research grant reviewer mentor for the Preparing Future Faculty active member of the American Society and panelist for the Life in Extreme program. Dr. Wood is a member of the for Microbiology (ASM), and served on Environments program, and has organized American Society for Microbiology and the editorial board of the journal Applied conference sessions on archaeal molecular the Association of College and University and Environmental Microbiology for nine biology and proteins from extremophiles. Biology Educators, as well as several local years and as Chair of the Division of Dr. Sandman has taught microbiology to organizations that foster pedagogy. She is General Microbiology. Dr. Willey taught hundreds of students, at both the a digital faculty consultant for McGraw- microbiology to biology majors for 20 years introductory level and in an advanced Hill and has worked on several textbooks and now teaches microbiology and molecular microbiology laboratory. in a variety of disciplines, developing and infectious disease to medical students. She Dr. Sandman has worked as a consultant editing digital content to accompany the has taught courses in cell biology, marine in a variety of industries, including texts. Outside of the classroom, Dr. Wood microbiology, and laboratory techniques in industrial microbiology, environmental is a fitness professional, leads health and molecular genetics. Dr. Willey lives on the geomicrobiology, and technical publishing. wellness seminars, and has been the north shore of Long Island and has two She lives with her husband in Columbus, treasurer of a nonprofit organization for grown sons. She is an avid runner and Ohio, and has two grown daughters. She the past 10 years. She enjoys life in enjoys skiing, hiking, sailing, and reading. enjoys biking, fabric arts, reading, and North Carolina with her husband and two She can be reached at joanne.m.willey@ genealogy, and can be reached at grown children and can be reached at hofstra.edu. [email protected]. [email protected]. iv wil11886_fm_i-xxiv.indd 4 23/10/18 2:12 pm  Digital Tools for Your Success Save time with auto-graded assessments. Gather powerful performance data. McGraw-Hill Connect for Prescott’s Microbiology provides online presentation, assignment, and assessment solutions, connecting your students with the tools and resources they’ll need to achieve success. Homework and Assessment With Connect for Prescott’s Microbiology, you can deliver auto-graded assignments, quizzes, and tests online. 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Please contact your Accessibility Services office and ask them to email [email protected], or visit www.mheducation.com/about/accessibility.html for more information. wil11886_fm_i-xxiv.indd 7 23/10/18 2:12 pm  A Modern Approach to Microbiology Brief Contents Evolution as a Framework Introduced immediately in chapter 1 and used as an overarching theme throughout, evolution helps unite microbiological con- About the Authors iv 25 Fungi 579 26 Viruses 594 cepts and provides a framework upon which students can build Part One Introduction to Microbiology their knowledge. 1 The Evolution of Microorganisms and Microbiology 1 Part Six Ecology and Symbiosis 27 Microbial Interactions 619 2 Microscopy 20 28 Biogeochemical Cycling and Global Climate 3 Bacterial Cell Structure 40 Change 632 4 Archaeal Cell Structure 77 29 Methods in Microbial Ecology 646 5 Eukaryotic Cell Structure 87 30 Microorganisms in Marine and Freshwater Ecosystems 658 An Introduction to the Entire Microbial World 6 Viruses and Other Acellular Infectious Agents 106 31 Microorganisms in Terrestrial Ecosystems 675 Covered in chapters 3–6, separate chapters on the structure and Part Two Microbial Nutrition, Growth, and Control 7 Bacterial and Archaeal Growth 128 Part Seven Pathogenicity and Host Response 32 Innate Host Resistance 693 function of bacteria and archaea are followed by the discussion 8 Control of Microorganisms in the Environment 9 Antimicrobial Chemotherapy 187 170 33 Adaptive Immunity 719 34 The Microbe-Human Ecosystem 752 of eukaryotic cells and viruses. 35 Infection and Pathogenicity 770 Part Three Microbial Metabolism 10 Introduction to Metabolism 209 Part Eight Microbial Diseases, Detection, and 11 Catabolism: Energy Release and Conservation 228 Their Control 12 Anabolism: The Use of Energy in Biosynthesis 265 36 Epidemiology and Public Health Microbiology 786 Broad Coverage of Microbial Ecology 37 Clinical Microbiology and Immunology 806 38 Human Diseases Caused by Viruses and Prions 825 Part Four Microbial Molecular Biology and Genetics 39 Human Diseases Caused by Bacteria 857 The importance and multidisciplinary nature of microbial ecology 13 Bacterial Genome Replication and Expression 288 40 Human Diseases Caused by Fungi and Protists 900 14 Regulation of Bacterial Cellular Processes 326 are demonstrated by content that ranges from global climate 15 Eukaryotic and Archaeal Genome Replication and Expression 355 Part Nine Applied Microbiology change to the human microbiome. 16 Mechanisms of Genetic Variation 375 17 Microbial DNA Technologies 405 41 Microbiology of Food 925 42 Biotechnology and Industrial Microbiology 944 18 Microbial Genomics 425 43 Applied Environmental Microbiology 960 Appendix 1 A Review of the Chemistry of Biological Molecules A-1 Part Five The Diversity of the Microbial World Appendix 2 Common Metabolic Pathways A-9 19 Microbial Taxonomy and the Evolution of Diversity 447 20 Archaea 466 Appendix 3 Microorganism Pronunciation Guide A-17 21 Nonproteobacterial Gram-Negative Bacteria 484 Glossary G-1 22 Proteobacteria 504 Index I-1 23 Gram-Positive Bacteria 537 24 Protists 559 34.3 A Functional Core Microbiome Is Required for Human Homeostasis 763 iii M cell Microbial genss g ntige ntige Antigens An Antigens Molecular Microbiology and Immunology Dendri endr icc itic e rritic Dendritic De celll cell cce 3 LC3 ILC3 IL The eleventh edition includes updates on genetics, biotechnol- Naive Na cellll aivve T ccel H an a i microbial icrobial ntti-micro anti-microbial gA IIgA ndrittic en Dendritic D e cell ogy, genomics and metagenomics, immunology, and the hu- TH LC3 C ILC3 IL man microbiome. A streamlined discussion of immunity, with enhanced detail between innate and adaptive linkages, helps B cell ell Stimulated B cell ce gA Ig IgAA+ A+ gA IIgA B cell students grasp the complexity and specificity of immune re- Peyer’s patch h gA g IgA Ig A+ B cce B-cell oo o ell po p oll o pool sponses. A new chapter, The Microbe-Human Ecosystem, in- ell T ce ependent dependent ell-d T-cell-dependent cel inndepe T-cell-independent T-cell-i T IgA i d tii I A induction i duction I A induction IgA ind troduces students to the development and impact of the human Figure 34.7 Production of SIgA Requires ILC3 and Microbial Stimulation. B-cell stimulation can be T-cell dependent (left, Peyer’s patch) or T-cell microbiome. independent (right, isolated lymphoid follicle). In both cases, innate lymphoid cells-3 (ILC3s) optimization of dendritic cell activity is needed. ILC3 function requires interaction with host microbes or their products. Intestinal Intestinal intrinsic nervous system, that is connected to the CNS via the lumen barrier CNS vagus nerve. Gut bacteria directly stimulate neurons within the enteric nervous system, which then communicate with the vagus nerve. The vagus nerve in turn transmits signals to the brain. The Immune system vagus nerve can differentiate between stimuli from normal mi- LPS crobiota and pathogens even in the absence of inflammation, al- Other microbial products though how this fascinating feat is possible remains under Vagus nerve investigation. Microbes signal enteric nervous Finally, as suggested by experiments in which butyrate and FMT had similar effects on the behavior of GF mice, soluble microbial products can impact the CNS. To understand this, Blood-brain barrier we must first consider the CNS as a site that is set apart from the remainder of the body by the blood-brain barrier (BBB). The SCFAs BBB is lined with cells that protect the CNS from normal blood components as well as toxins and infectious agents. This is Figure 34.8 The Gut-Brain Axis. Gut microbes influence the central largely due to impermeable connections, called tight junctions, nervous system using at least three mechanisms. LPS, lipopolysaccharide; between the cells that make up the BBB. Once again, a flurry of SCFAs, short-chain fatty acids research was triggered by an observation made in GF mice: (right top) ©GraphicsRF/Shutterstock Their BBBs have the undesirable quality of being more permea- ble than conventional mice. And once again, it is SCFAs, par- viii of appetite, decreased motor activity, loss of sociability, and re- duced cognition (“trouble thinking”). ticularly butyrate, that help maintain the BBB as an impenetrable barricade. Because SCFAs are most abundant when mice or hu- Another mechanism that helps mediate the gut-brain axis is mans eat a high-fiber diet, the broader implication is that one’s a direct pathway from gut to brain. This is possible because the diet can govern the entry of metabolites and other blood-borne GI tract is lined with a network of nerves, called the enteric or compounds to the CNS. wil11886_fm_i-xxiv.indd 8 23/10/18 2:13 pm  A Modern Approach to Microbiology 17.5 Cas9 Nuclease Is a Precise Tool for Genome Editing 421 17.5 Cas9 Nuclease Is a Precise Tool procedures are general enough to be used for any cell into which DNA can be introduced and expressed. infection (section 14.6) Responses to viral 21st-Century Microbiology for Genome Editing Prescott’s Microbiology leads the way with text devoted to global Like restriction enzymes, Cas9 is an endonuclease that cuts After reading this section, you should be able to: both strands of a target DNA. However, there is an important difference between the two types of nucleases, in terms of how a. Distinguish the DNA recognition features of restriction endonucleases and Cas9 nuclease they recognize their target sequence in double-stranded DNA. Restriction enzymes recognize four to eight base pairs through climate change, biofuels, and microbial fuel cells. For more, see chapters 28, 30, 42, and 43. b. Explain how Cas9 nuclease can be directed to cut at a unique site in contacts between the DNA molecule and amino acid side chains a genome in the enzyme (figure 17.2). Cas9, however, is a ribonucleoprotein c. Diagram how a new gene may be inserted into a chromosome by consisting of a polypeptide and a guide RNA (gRNA). Recogni- homologous recombination tion of target DNA for cleavage occurs by hybridization of about 20 bases between the gRNA and its complementary DNA se- Cas9 genome editing has rapidly become one of the most widely quence in the genome (figure 17.13). used tools for altering genomes in vivo. Cas9 genome editing is In microbes, the CRISPR locus is the source of the gRNA often referred to as CRISPR or CRISPR-Cas9, referencing the (see figure 14.27), and the Cas9 nuclease protects the cell from bacterial genome element from which it was developed, but in fact, only the Cas9 component is used in editing. Cas9 nucleases are encoded in the genomes of most bacteria and archaea, where viral attack. Sequences in the CRISPR locus derive primarily from mobile genetic elements (bacteriophage and plasmids), so Metagenomics and the Human Microbiome the Cas9 nuclease in a microbial cell specifically targets invad- they are usually adjacent to a CRISPR locus, clustered regularly interspaced short palindromic repeats. As the mechanistic de- ing DNA for destruction. The extreme specificity conferred by the gRNA is the key to genome editing because each 20-base The importance of metagenomics in understanding the role of tails of Cas9 function were discovered, two research groups, one led by Jennifer Doudna and Emmanuelle Charpentier and the other by Feng Zhang, sought to adapt Cas9 for genome editing. target sequence is almost certainly unique, even in a large eu- karyotic genome. In contrast, a restriction enzyme that recog- microbes in all environments and in exploring symbionts of in- In this process, genomic DNA can be directly modified and the nizes a few nucleotides will cut the genome, on average, every few thousand bases. vertebrates is threaded throughout the text. A new chapter, The Microbe-Human Ecosystem, explores the human microbiome. gRNA Cas9 nuclease DNA:RNA hybrid Laboratory 876 | Safety CHAPTER 39 Human Diseases Caused by Bacteria Reflecting recommendations from the Centerswefor know Disease Con- Genomic DNA Cas9 nuclease cuts about the progression and both DNA strands. prognosis of syphilis is based on trol and Prevention, along with the American Society shameful studies performed in for the Serologically positive United States during the twentieth Microbiology, chapter 37 provides specific guidance century (Diseasefor 39.1). labora- % Cases reactive 100 Diagnosis of syphilis is through tory best practices to help instructors provide safe history,conditions The double-strand break is repaired The double-strand break is repaired by by non-homologous end joining. homologous recombination with donor DNA. 90 clinical Secondary physical examina- tion, and immunoassay. Two tests, eruption Recrudescent during the teaching of laboratory exercises. tory (VDRL) and rapid Tertiary 80 the venereal disease research labora- secondary Early Late stage Primary eruptions 70 chancre plasmin re- latent latent Donor DNA stage stage agin (RPR), measure the production 60 of antibody made in response to host cells damaged by T. pallidum. These 0 are called nontreponemal tests be- Figure 17.13 Genome Editing with Cas9 Nuclease. 10–90 3–8 weeks 4–12 weeks cause they do not detect spirochete- MICRO INQUIRY How could you assemble the donor DNA molecule for homologous recombination? days specific antibody. Diagnosis is made 6 weeks– 2 years 10 years 6 months by pairing a nontreponemal assay Exposure after after interval primary primary (i.e., VDRL or RPR) with a trepone- between primary and chancre chancre mal specific test, such as the T. pal- secondary stages lidum particle agglutination (TPPA) Figure 39.18 The Course of Untreated Syphilis. test, which detects antibodies made Special Interest Essays Organized into four themes—Microbial Diversity & Ecology, Techniques & Applications, Historical Highlights, and Disease— DISEASE these focused and interesting essays provide additional insight 39.1 Syphilis and the Tuskegee Study into relevant topics. A research investigation named “Tuskegee Study of Un- The “Tuskegee Study,” as it was known, started with a 27.2 Mutualism and Cooperation Are Two-Way Interactions 621 treated Syphilis in the Negro Male” would be unthinkable racist objective—to develop syphilis treatment for black peo- today. But it was the reality in 1932 Macon County, Alabama, ple. The enrollees were provided free medical checkups, when the federal Public Health Service began the study on meals, and burial assistance, but were not told the study had 600 black men (399 with syphilis, 201 without the disease). anything to do with syphilis. Rather, they were informed that MICROBIAL DIVERSITY & ECOLOGY The tale of this study and its participants is a stain on the his- they were being treated for “bad blood” (box figure). Except tory of U.S. public health, for which President Bill Clinton they weren’t being treated. Even after penicillin was shown to 27.1 Wolbachia pipientis: The World’s Most Infectious Microbe? formally apologized in 1997. be a highly effective cure for syphilis in 1947, treatment was withheld. The project was supposed to last 6 months; it went Most people have never heard of the bacterium Wolbachia However, the mosquito vectors of these viruses, which pipientis, but this rickettsia infects more organisms than any belong the genus Aedes (box figure), are not natural hosts to on for 40 years. other microbe. It is known to infect a broad range of crusta- Wolbachia. Nonetheless, infection can be established by Finally in July 1972, a newspaper story broke the news ceans, spiders, mosquitoes, millipedes, and nematodes, and transinfection, the process of transferring the microbes from that men were unknowingly enrolled in this highly unethical may infect more than 2 million insect species worldwide. To another insect species. Many Wolbachia isolates have been study and a government panel confirmed that study partici- what does W. pipientis owe its extraordinary success? Quite screened for those that have the most severe effects on Ae­ simply, this endosymbiont is a master at manipulating its des, and several stable insect strains have been established pants had been misled and appropriate medical treatment had hosts’ reproductive biology. with Wolbachia from Drosophila. Cytoplasmic interference been withheld. At this time, it was also revealed that the men W. pipientis inhabits the cytoplasm of its host’s cells and is extensive in these strains of Wolbachia. To establish a were never given the opportunity to quit the study. Three is transferred from one generation to the next through the stable population of Aedes outside the laboratory, it is impor- eggs of infected females. To survive, Wolbachia must ensure tant that the infection not impose a dramatic burden on the months later, the panel shut down the study. the fertilization and viability of infected eggs while decreas- insect, as it must compete with and integrate into wild The following year, a class-action lawsuit was filed on ing the likelihood that uninfected eggs survive. The mecha- populations. behalf of the study participants. In 1974, a $10 million settle- nism by which this is accomplished depends on the host. In In a promising development, Wolbachia-infected Aedes ment was reached. The U.S. government also promised to wasps and mosquitoes, W. pipientis causes cytoplasmic in- mosquitoes are effective at blocking the transmission of both compatibility, which means that embryonic development will Zika and dengue viruses. Experiments in Australia have con- provide lifetime medical benefits and burial services for all be abnormal if only the male is infected. For instance, when firmed the ability of these insects to persist and spread in lo- enrollees. In 1975 the wives and children of the men partici- infected sperm of the wasp Nasonia vitripennis fertilizes un- cal mosquito populations, validating this approach to insect pants were added. The last study participant died in 2004 and infected eggs, chromosomes from the W. pipientis–laden vector control. there are currently 12 offspring receiving benefits. Source: CDC sperm prematurely try to align with the egg’s chromosomes. These eggs then divide as if never fertilized. However, chro- mosomes behave normally when an infected female mates with an uninfected male. This yields a normal sex distribu- tion, and all progeny are infected with the rickettsia. In other infected insects, W. pipientis may simply kill all the male offspring and induce parthenogenesis in infected females; that is, the females simply clone themselves. This limits genetic diversity but allows 100% transmission of rickettsias to the next generation. In still other hosts, the microbe modifies male hor- mones so that the males become feminized and produce eggs. Another effect of Wolbachia infection is interference with viral replication. Viruses normally spread by insects may not be transmissible if the insect is infected with Wolbachia. This has led to the notion that this infection could be used as a means of biological control. Aedes mosquitoes transmit numer- ous viruses, like Zika, dengue, chikungunya, and West Nile. Female Aedes aegypti mosquito. Infection with Wolbachia may render In humans, these viral infections have no cure and no treatment these insects incapable of spreading arboviruses to humans. beyond supportive care, so insect control is the best prevention. Source: CDC/James Gathany For most microbial ecologists, the nonobligatory aspect between Mutualism defines the relationship in which some reciprocal host and symbiont differentiates cooperation from mutualism benefit accrues to both partners. This is an obligatory relationship (Latin mutuus, borrowed or reciprocal) (figure 27.1). Unfortu- in which the mutualist and the host are dependent on each other. nately, it is often difficult to distinguish obligatory from nonobligatory because that which is obligatory in one habitat In many cases, the individual organisms will not survive when separated. Several examples of mutualism are presented next. ix may not be in another (e.g., the laboratory). Nonetheless, the most useful distinction between cooperation and mutualism is Microorganism-Insect Mutualisms the observation that cooperating organisms can grow indepen- Mutualistic associations are common between microbes and in- dently, although they may not function as well. sects partly because insects often consume plant sap or animal wil11886_fm_i-xxiv.indd 9 23/10/18 2:13 pm  Student-Friendly Organization 38 Micro Focus—Each chapter begins with a real-life story illustrating the relevance of the content covered in the up- Human Diseases coming text. Caused by Viruses and Prions Source: Photographs in the Carol M. Highsmith Archive, Library of Congress, Prints and Photographs Division Remembering HIV/AIDS will be entirely novel, like severe acute respiratory syndrome (SARS) and HIV. Most, like the SARS virus, will “burn out” through a combination of I f you are young, you do not remember the early days of human immunodeficiency virus (HIV) when large swaths of communities died. preventative measures and mutation. Others, like Zika virus, will cause devastating illness before they are brought under control. And others, like Readiness Check—The introduction to each chapter in- cludes a skills checklist that defines the prior knowledge HIV, will cause pandemics and global crises. In all cases, the destruction You do not remember how a young hemophiliac named Ryan White had to viruses cause seems incongruent with their size and relative simplicity. fight, and then move to a new community, to attend middle school. You do Chapters 6 and 26 review the general biology of viruses and not remember highly visible public statements that HIV/AIDS was God’s punishment. You do not remember high-level U.S. government officials introduce basic 50virology. 3 | Bacterial In chapter CHAPTER Cell Structure 38, we continue this coverage by discussing some of the most important viruses that are human pathogens. students need to understand the material that follows. who would not mention the term “HIV/AIDS” or the South African president We group viral diseases according to their mode of acquisition and who told his citizens that HIV did not cause AIDS and denied access to transmission; viral diseases that occur in the United States are drugs that would prevent maternal-fetal transmission. You probably don’t Phosphate is then transferred emphasized. to incoming sugar via EIIB. Green - Fe3+ remember the quilt that toured the United States (shown here), each patch Red - O Mannitol-1-P telling the story of a life cut short. Gray - C Readiness Check: Blue - N That’s because you were probably born after 1996, when highly Based on what you have learned previou