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Sheela Srivastava Sheela Srivastava Genetics of Bacteria Genetics of Bacteria Sheela Srivastava Genetics of Bacteria 123 Sheela Srivastava Department of Genetics University of Delhi, South Campus New Delhi, Delhi India ISBN 978-81-322-1089-4 ISBN 978-81-322-1090-0 (eBook) DOI 10.1007/978-81-322-1090-0 Springer New Delhi Heidelberg New York Dordrecht London Library of Congress Control Number: 2013930625 Ó Springer India 2013 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Exempted from this legal reservation are brief excerpts in connection with reviews or scholarly analysis or material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher’s location, in its current version, and permission for use must always be obtained from Springer. Permissions for use may be obtained through RightsLink at the Copyright Clearance Center. Violations are liable to prosecution under the respective Copyright Law. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. While the advice and information in this book are believed to be true and accurate at the date of publication, neither the authors nor the editors nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) Preface From the time microorganisms could be seen, described, and studied, they have provided a useful system to gain insight into the basic prin- ciples of life, though we are still far from understanding them fully. The relative simplicity, which may often be deceptive, made microbes ideally suited for answering some very fundamental questions in science. Microorganisms have been employed in almost all fields of biological studies, including the science of Genetics. The whole edifice of classical genetics centers around three processes viz, the generation, expression, and transmission of biological variation. Thus, the most crucial requirement of genetic analysis is to select or introduce variations in a specific gene (mutation\s). Even with the rapid growth of modern molecular biology, the relevance of genetic analyses that depends on finding the mutants and using them to elucidate the normal structure and operation of a biological system has not been lost. Mutation may lead to an altered trait in an organism and if the change takes place in the observable characteristics (phenotype) of that organism, this could be used to follow the transmission of the said gene. The genetic composition (genotype) of the organism could be inferred from the observable characteristics. With the improved biochemical techniques and instrumentation, and the revelation of the chemical nature of the gene (DNA, RNA in some viruses), it became possible to dissect the gene expression/function at the molecular level. In all these studies, gene mutations occupied the center stage. Gene cloning and other techniques of gene manipulation provided a new direction, as the genes could be isolated and studied without a prior requirement of obtaining mutants. Moreover, these genes could be altered specifically and in a desired manner in vitro (site-directed mutagenesis). However, deriving the gene function by its alteration never lost its relevance. Also, it should become clear that most genes do not function in isolation and its real understanding can come through in vivo analysis only. When microorganisms, first fungi and then bacteria, were employed as model systems in genetic analysis, they offered immediate advantages in studying all the three aspects of heredity: being haploid and struc- turally simpler it became easy to isolate mutations of various kinds and relate them to a specific function. Though very few morphological v vi Preface mutants could be obtained, a whole range of biochemical mutants became available in a very short time. The availability of these mutants and their amenability to detail genetic and biochemical analyses led to the generation of a whole lot of information about gene expression and its regulation. So much so, that they provided the first clues, and the platform for studying the complex eukaryotic systems. It was when transmission of biological variation was to be studied that a different strategy had to be employed. While in higher organisms, such a line of study would require phenotypic markers in a controlled hybridization, in microorganisms, especially bacteria, a more genetic approach needed to be employed. Both bacteria and their viruses and fungi have been extensively exploited for genetic analyses. The information so generated became so vast that creation of a branch of Microbial Genetics became thoroughly justified. Microorganisms have not attempted to alter any established genetic concept but the technique applied to them and the way the results are to be interpreted are so different from higher organisms that their clubbing together may cause some confusion. In the same vein, fungi and bacteria represent two entirely different types of biological systems, i.e., eukaryotic and prokaryotic, respectively. Thus, it would not be inappropriate to treat them separately. Bacteria, the simplest of the living organisms, have provided enough material on all aspects of genetics. In any compendium, however, the treatment of these aspects may be very different. In most basic genetics books, bacterial genetics may occupy the place of a chapter with information about mutation and expression combined with other eukaryotes. Some books dealing with microbes or more correctly with bacteria alone are also available and have served the purpose of a useful resource book on Microbial Genetics to teachers as well as students. While teaching a course on Microbial Genetics for the last 25 years to post-graduate students at Delhi University, I have realized that a book on Bacterial Genetics may be very handy to students, researchers, and teachers alike. However, a new format has been planned for this book where emphasis has been on the transmission aspects, along with giving due share to the generation of biological variation, because without the latter, the former is not possible. The omission of expression part has indeed been intentional. And the reason: a large volume of information available on this aspect in books dealing with genetics, biochemistry, cells biology, molecular biology, and biotechnology. Thus, the inclusion of such information would only have amounted to repetition. Bacterial genetics is moving through an important phase in its history. While on the one hand, this field of study continues to remain instru- mental in the development of new tools and methodologies for better understanding of molecular biology, on the other, it provides scientists with a strong handle whose ultimate impact is hard to foresee. In addition to providing an insight into basic biological questions, genetic knowledge can also be used to manipulate biological systems for sci- entific or economic reasons. Traditionally, genetic manipulation Preface vii requires mutagenesis, gene transfer, and genetic recombination followed by selection for desired characteristics. However, with such techniques, geneticists are forced to work with random events with selection often quite complex to detect rare mutations with the desired genotypes. Moreover, the nature of the gene and its function in most cases often remain unclear. The application of microbial genetics led to the accumulation of a huge body of knowledge and a continually greater understanding of the nature of genes. The basic research in microbial genetics has not ceased but continues to reveal phenomena important to the understanding of life and its processes as a whole. So, while bacterial genetics paved the way for studying genetic systems other than bacteria, it also ventured to provide solutions for specific industrial, environmental, ecological, pharmaceutical, and other problems. In the early 1970s, microbial genetics itself underwent a revolution with the development of the recombinant DNA (r-DNA) technology. Through these remarkable but straightforward biochemical techniques usually called genetic engi- neering or gene cloning, the genotype of an organism can be modified in a directed and pre-determined way. The r-DNA technology, in fact, ushered in the era of manipulation of DNA outside the cell, recombi- nation in vitro, and reintroduction of recombinant DNA into a new cell. In this way, novel organisms with characteristics drawn from distant species and genera can be created. For example, human genes can be transferred to a bacterium, and a bacterial gene placed into plants or animal cells. In fact,
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