This is the first volume to bring together the studies on the differences and profound similarities in the molecular mechanism of virulence between bacteria pathogenic for humans, animals and plants. The volume contains the following sections: 1. Host cell recognition and binding; 2. Pathogen ingression and invasive mechanism; 3. Enzymes, toxins and other pathogenic factors; 4. Regulation of virulence genes and signal transduction; 5. Pathogen of host-defense mechanisms.