Prescott�s Principles of Microbiology continues in the tradition of the market leading Prescott, Harley, and Klein�s Microbiology. In using the 7th edition of PHK�s Microbiology as the foundation for the development of Principles, the authors have presented a streamlined, briefer discussion of the broad discipline of microbiology and have focused on readability and the integration of several key themes with an emphasis on evolution, ecology and diversity throughout the text. To accomplish this, each chapter focuses on key concepts and includes only the most relevant, up-to-date examples. Unique to Principles is the inclusion of microbial pathogens into the diversity chapters (chapters 19-24). Thus when students read about the metabolic and genetic diversity of each bacterial, protist, and viral taxon, they are also presented with the important pathogens. In this way, the physiological adaptations that make a given organism successful can be immediately related to its role as a pathogen and pathogens can be readily compared to phylogenetically similar microbes.