Bacteria occupy a unique position in the living world. They are amongst the first inhabitants of planet earth, and have survived until the present day. Adaptation, adjustment, and accommodation are the hallmarks of their strategy for survival. Their structural simplicity, and yet independent lifestyle, has provided a baseline model system on which every branch of modern biology have been founded. This includes the fields of molecular genetics and recombinant DNA technology. Bacteria have been at the heart of developments in the field of biotechnology where today many microbial and eukaryotic (including human) metabolites have found industrial applications. Amenable to all modern tools and techniques, bacteriology has developed an interface with all other branches of biology, often providing the major leads and clues. In the present era of genomics, now that many microbial genomes have been sequenced, bacteria are destined to provide new information that will further our understanding of life and biological processes. This book contains exhaustive information on almost all aspects of bacteria. The book deals exclusively with bacteria and includes the entire gamut of bacteriology. It will be useful to graduate and post-graduate levels but also to established researchers. The book is organized in such a way that it will give the reader an overview of our current understanding of bacteria. It will explain the categories under which various types have been grouped and describe the versatile range of metabolic processes which can be found in these microbial organisms. Their metabolic regulation, capacity to change and keep evolving and their pivotal role in natural processes are highlighted. Research on bacteria, especially genetic engineering, will have far reaching applications in the future.