Abstract
Microbial Toxins. Molecular and Cellular Biology, edited by Thomas Proft, is a collection of reviews addressing issues associated with bacterial and fungal toxins. The book contains 20 chapters, each dealing with different aspects in this area of current interest and scientific research. The book is not formally divided into sections, but three main topic areas are covered: mechanisms and modes of action of microbial toxins, effects of specific toxins on biological systems, and what could be called “practical” uses of microbial toxins. Although more than half of the contributors to this work are from the United States and New Zealand (the editor’s home country), authors from 11 different countries have collaborated in this collection of reviews.
Chapter 1 of this book is an introduction and overview of the topics that are considered in detail in subsequent chapters. Chapters 2 through 6, 17, and 18 concern themselves with the general mechanisms of the toxic effects of microbial agents. Chapters 17 and 18 could have logically come earlier in this volume for consistency of organization. Chapter 2 discusses bacterial proteins that exert toxic effects by adenosine diphosphate (ADP)-ribosylation of G-proteins. These include the toxins produced by the bacteria Vibrio chloerae (cholera), Escherichia coli, and Bordatella pertussis (pertussis). As well as describing the modes of actions of these toxins, the authors describe recent elucidations of the three-dimensional (3-D) structures of these proteins and how those structures affect protein assembly, cell binding, and toxin activation.
The authors of Chapter 3 in this book provide the reader with an understanding of bacterial toxins that modify the actin cytoskeleton of cells. These include the toxins of Clostridium botulinum (botulism), Salmonella (food poisoning), Yersina (plague), and Listeria (listeriosis). This chapter also covers the effects of these and other bacterial toxins on Rho GTPases. Chapter 4 covers the class of bacterial protein agents known as “cytolethal distending toxins” (CDTs). The major effect of CDTs is to cause eukaryotic cells to become irreversibly blocked in the G1 or G2 phase of the cell cycle. Bacteria that produce this type of toxin include those responsible for gastrointestinal infections (Campylobacter jejuni, some E. coli species, and Shigella) and Helicobacter hepaticus that can cause hepatitis. The genetics of CDTs and their interactions with the mammalian immune system are also discussed in this chapter.
Chapter 5 discusses those toxins that interfere with cellular protein synthesis. Bacteria produce these toxins to gain access to nutrients for their own growth and proliferation, to promote their transmission, and to disable host immune defense mechanisms. These toxins include those produced by Corynebacterium diphtheriae (diphtheria), Pseudomonas aeruginosa (infections of a variety of organs), and Shigella (dysentery). The crystal structure, cell receptors, and modes of action of these pathogens are covered in this chapter. In Chapter 6, the author looks at bacterial agents that gain access to cells by damaging host cell membranes, or by forming de novo pores in those membranes. The effects of these agents are to cause tissue necrosis that provides a source of nutrients for the invading bacteria and to facilitate the transmission and/or secretion of bacterial proteins into the host cells. Some examples of bacteria producing membrane-damaging toxins include E. coli, Helicobacter pylori (peptic ulcers), and Staphylococcus aureus (food poisoning).
Chapters 7 through 16 give overviews of the toxic actions of specific microbial toxins. Most of these chapters cover the structures and genetics of the toxins and the cellular targets and modes of actions of the toxins. The diseases caused by these microbial agents are also discussed. Chapter 7 concerns tetanus and botulinus toxins. Chapter 8 looks at toxins that target the immune system, the so-called “superantigens”. Chapters 9, 10, and 11 specifically address invasive Streptococcal disease, Staphylococcus aureus pathogenicity, and Bacillus anthracis (anthrax), respectively. Chapters 12 through 15 contain detailed discussions of Clostridium toxins, Shiga toxin, Yersina toxin, and the bacteriocins (toxins produced by bacteria to kill other bacteria). Chapter 16 is the only one in this book that exclusively addresses nonbacterial microbial toxins: the mycotoxins produced by molds and other fungal organisms.
Chapters 17 and 18, which as mentioned earlier, could have perhaps more logically followed Chapter 6 of this book, deal with host cell penetration and movement of bacterial protein toxins within the cell and with the regulation of bacterial toxin expression. The discussions in these two chapters are of a more general nature and would seem to have been better placed along with those earlier chapters that addressed more general mechanisms of toxic actions.
Chapter 19 is an interesting review of how our knowledge of the modes of action of bacterial infections can be used in beneficial ways. The fact that bacteria have evolved methods by which they can transmit their proteins into host cells implies that modified bacterial toxins can make excellent delivery devices for vaccines, antitoxins, and antimicrobial agents. This is an active area of current scientific interest and research. The final chapter in this book is entitled “Microbial Toxins as Potential Tools in Bioterrorism.” The author of this chapter notes that although biological warfare is far from a novel concept in human history, concern over national security and the possibility of the use of biological “weapons of mass destruction” has never been greater. The use of agents such as botulinum toxin, Bacillus anthracis, Variola virus (smallpox), and mycotoxins are covered in this chapter. Some of the background information about mycotoxins found in this chapter is duplicative of that in Chapter 16 of the book. This is not a major shortcoming of this work, however, since many readers specifically interested in bioterrorism may not be interested in reading the whole book anyway.
The strengths of this book include the international nature of the contributors, the comprehensiveness of the presentations, the multitude of cited references, and the timeliness of the material. As mentioned previously in this book review, the contributors to this book hail from more than 10 different countries. Having such a diverse group of authors provides a wider view of the research in this field being conducted around the world. Because each chapter is essentially a review article, the breadth and depth of the information provided are substantial. This is reflected in the sheer numbers of cited works for each chapter of the book. The authors of some chapters cite more than 200 reference works each and the total number of references in this book exceeds 2500.
Each chapter’s authors have made it a point to present the most up-to-date and timely information in this rapidly expanding area of scientific inquiry. Nearly every book on areas of science in which research is on-going will inevitably be somewhat out of date by the time it is published and disseminated. The efforts of the contributors to this book to seek out and include the most current research findings and to cite the most recent literature make it more timely than most. At the very least, this work provides an excellent starting point for individuals interested in pursuing additional research on these topics.
All in all the book is well written, although at times the use of jargon and acronyms will make for slow reading for all those not especially familiar with the particular areas of research described. The inclusion of a glossary at the end of the book or glossaries for at least some of the individual chapters might have made some sections more “reader friendly.” There were also some minor inconsistencies in the text. Some chapter authors used U.S. spellings of certain words (e.g., realization, odors), whereas others used British spellings (e.g., realisation, odours). Several different variants of the “A-B” notation for the general type of toxins most commonly described in this book were used in different chapters (e.g., A-B, AB, A:B,
Another improvement that could be made in this book would be the greater use of color in the figures and diagrams. The color plate on page 290 is the only one in the whole book. In many cases the authors used shades of gray in figures to attempt to denote different parts of protein molecular structures. Using color for these figures would have made for easier comprehension. Pictures of histological slides (e.g., on page 224) would be much more informative if they had been in color as well. In a book that sells for $250, one might expect a more liberal use of color prints. This price may also limit the number of people who buy this book. Books of similar size and content are more likely to cost about $100.
The author of the introductory chapter of the book indicates that the relevant audience for this compendium would be students, researchers, clinicians, medical microbiologists, biologists, and biochemists. The book is most likely to be useful to the latter three types of individuals, especially the sections dealing with the use of the findings from bacterial toxin research to elucidate the mechanisms of cellular function and biochemistry. Researchers could also rely on this work because most of the contributors to this book have identified areas in which more knowledge is needed. This book could also be used as a resource for students, but probably only for more advanced undergraduate or in graduate school courses. Most clinicians would probably not have the time or need to go to the level of detail provided in this book. They would be more likely to rely on other texts more geared to the specifics of the diagnosis and treatment of human diseases.