This book, comprising 16 chapters, covers various aspects of microorganisms as natural resources for sustainable agriculture. The composition of media used for culturing the microorganisms and methods are also listed in this book. Figures with updated information are a salient feature of this book. Selected references, suggested readings, glossary of terms used are given at the end of the book. The book is written as per the syllabi of the various universities. This will form a textbook for both UG and PG level of traditional universities, agricultural universities, industrial microbiology, microbial biotechnology, microbial ecology, applied microbiology and plant pathology. It also is a very good source for general reading for all, including candidates participating in various competitive examinations.