Flagella-dependent motility is widespread throughout prokaryotes and is advantageous when nutrients are limited as a mechanism to migrate to more favorable environments and to compete with other micro-organisms. Flagella systems can also play an important role in additional processes, such as adhesion to substrates, biofilm formation, and host invasion in pathogenic bacteria. A variety of different classes of pili are found in prokaryotes and these structures also possess a diverse array of functions. Pili are essential for host colonization, virulence, and pathogenesis for many bacteria and, in the case of type IV pili, can also be employed for motility across solid surfaces. This book brings together some of the top scientists in the field and describes the current knowledge and latest research on prokaryotic pili and flagella. The emphasis is on the molecular biology, genetics, structure, assembly, and function of these structures. Topics include: biogenesis, structure, and function of various pili in Gram-negative and Gram-positive organisms * flagellar gene expression, structure, and assembly * the flagella motor * posttranslational modifications of flagella systems * lateral flagella systems * the origin and evolution of flagella * applications of flagella as a surface display and expression system * the flagella and pili of Archaea.