This first edition of the book entitled "An Orchid and Bacterium: Lesson in Plant-Microbe Interaction" focus on Diazotrophic and endophytic bacteria from Velamen tissues of Orchid, their metabolism, interactions with plant cell and functions within their hostile environment. Biotechnology of diazotrophicendophytes and their potential agricultural and industrial applications is the focus of this edition. However, this plant-microbe interaction may cope with their challenging environments. Information on their interactions with the surrounding cells helps in understanding their ecology and functions within their respective endophytic environments. This book is of interest to teachers, researchers, microbiologists, capacity builders and policymakers. Also, the book serves as additional reading material for undergraduate, graduate and research students of agriculture, forestry, ecology, soil science, microbiology, biotechnology and environmental sciences