The present second edition of Microbial Physiology is an improved and enlarged version of the first edition. It provides a detailed account of all aspects of physiology of microorganisms in an ordered sequence with profuse illustrations. Presentation of all chapters is based on the principles of bioenergetics which forms the life line for all metabolic functions. In this edition, new chapters on enzymes, metabolism of amino acids, lipids and nucleic acids; and microbial toxins, antimicrobial agents and signal transduction system are included. Thus, it provides a strong foundation and general framework for understanding the subject. This book not only serves as the text book for undergraduate, post-graduate students, but also as a reference book to teachers, researchers and all others interested in the metabolism of the microorganisms.