Brucella is a genus of Gram-negative, facultative, intracellular bacteria that are highly pathogenic for a variety of mammals, including humans. Recently the WHO cited brucellosis to be the world's most widespread zoonosis. An important feature of the pathogenicity of these organisms is their ability to survive and replicate within the host macrophages. However the mechanism for this is unclear. In addition, none of the classical bacterial virulence factors found in other bacterial pathogens have been found in the genomes of the forty Brucella species and biovars analysed to date. Nevertheless the application of systems biology approaches in recent years has transformed research, permitting fascinating new insights into Brucella molecular biology and genomics. Written by highly acclaimed Brucella scientists, this book comprehensively reviews the most important advances in the field. Opening chapters focus on genetic diversity within Brucella, covering both classical and new species. Pa