This book describes the major achievements and discoveries relevant to bacterial protein toxins since the turn of the new century illustrated by the discovery of more than fifty novel toxins (many of them identified through genome screening). The establishment of the three-dimensional crystal structure of more than 20 toxins during the same period offers deeper knowledge of structure-activity relationships and provides a framework to understand how toxins recognize receptors, penetrate membranes and interact with and modify intracellular substrates.