The Book “Elementary Microbiology” has been prepared for B.Sc III Year Students of Deen Dayal Upadhyaya, Gorakhpur University, which is a part of Paper I “ Microbiology and Plant Pathology”. In this book an attempt has been made to present the gist of the subject in a simple language and with suitable diagrams and it is hoped that this would be of some help to the students. The e-book contents are extracted/modified/compiled from various sources like research articles and freely available internet websites. It is organized for students to provide them the total content of Paper 1 microbiology in one place. I acknowledge all the authors whose contents has been helpful in some or other ways in formation of this book. At last, but with deepest gratitude, I am thankful to the almighty God and deep, unfailing, supportive affection of my husband “Sri Abhai Kumar Srivastava” so that I was able to compile this work.