Transcription is part of the process of gene expression and is very different in prokaryotes and eukaryotes. In prokaryotic cells the synthesis reactions of D.N.A., R.N.A. and proteins are intricately coupled as there are no subcellular compartments. Thus replication, transcription and translation occur simultaneously without local separation and the regulations of each is inter-related. In bacteria, regulation is most important at the transcription stage of the biosynthetic process, and changes in the transcriptional efficiency account for major differences in the frequency of R.N.A. formation and gene expression. This textbook has been written by an authority in the field for advanced students and postgraduates. Both clear and concise, there is an emphasis on transcription in bacterial and phage expression systems, a key area of study and research in molecular biology. Many general mechanisms and principles emerge from studies of prokaryotic transcription complexes that help build an understanding of regulation in higher organisms. Taking a biophysical approach, the text draws together elements of molecular biology, genetics, structural biology and biochemistry to provide an invaluable summary of the field of prokaryotic transcription regulation for students in molecular biology and related areas of study such as microbiology and biotechnology. Additional content information: this book includes -new data on the composition and architecture of R.N.A. polmerase - new findings on sigma- and anti-sigma- factors -a description of promoter elements underlining the importance of upstream and downstream flanking sequences -detailed kinetic description of the initiation process -new data on the function of D.N.A. curvature and topology on transcription -general mechanisms of repression -positive regulation -termination, anti-termination and attenuation mechanisms -implications of the nascent R.N.A. structure in regulation -