Infectious diseases caused by bacteria remain a leading cause of death worldwide. Many of the antibiotics developed to combat bacterial infections have been rendered almost impotent due to the rapid evolution and spread of antibiotic resistance. A common and major resistance mechanism - the efflux system - enables bacteria to extrude structurally diverse antimicrobials, facilitating survival in toxic environments. The pumps also have important physiological functions, play major roles in bacterial pathogenesis, and are distributed widely across diverse bacterial species. In addition, a single species may harbor several different types of efflux systems: of these, active efflux has proven to be one of the most successful detoxification mechanisms used by both Gram-positive and -negative pathogens. Unraveling the intricacies of the microbial efflux systems is essential for the development of new strategies to overcome antimicrobial resistance. This has inspired a plethora of multidisciplinary research projects that have focused on the biochemistry, bioinformatics, structural biology, and molecular biology of this fascinating field. With contributions from leading researchers in the field, this book reviews the most important current research and summarizes the most spectacular discoveries. It will be essential reading for all scientists with an interest in drug and antibiotic resistance in a range of different microorganisms.