This book, the first of its kind by Indian authors, tries to develop a comprehensive understanding of microbial metabolism. It deals with all basic and unique physiological aspects of microorganisms in an ordered sequence with profuse illustrations. Discussion of all chapters is based on the concepts of bioenergetics which form the life-line of metabolic functions. It provides the foundation and general frame work for further understanding of the subject. This book not only serves as a text for undergraduate, post-graduate students, but also as a reference book to teachers, researchers and all others interested in the metabolism of the microorganisms in particular and living organisms in general.