Microbes play an important role in our everyday lives. As agents of infectious disease they cause untold human misery, yet their beneficial activities are manifold, ranging from the natural cycling of chemical elements through to the production of food, beverages and pharmaceuticals. In this introductory level text the authors provide a clear and accessible account of the interactions between microbes, their environment and other organisms, using examples of both beneficial and adverse activities. The book begins by considering beneficial activities, focusing on environmental microbiology and manufacturing, and then moves on to consider some of the more adverse aspects, particularly the myriad of diseases to which we are susceptible and the treatments currently in use. This book is the companion to Introductory Microbiology, also published in this series, and is essential reading for biological science and medical undergraduates, as well as being of interest to sixth form students and their teachers.