The true extent of prokaryote diversity, encompassing the spectrum of variability among bacteria, remains unknown. Current research efforts focus on understanding why prokaryote diversification occurs, its underlying mechanisms, and its likely impact. The dynamic nature of the prokaryotic world, and continuing advances in the technological tools available make this an important area and hence this book will appeal to a wide variety of microbiologists. Its coverage ranges from studies of prokaryotes in specialized environmental niches to broad examinations of prokaryote evolution and diversity, and the mechanisms underlying them. Topics include: bacteria of the gastrointestinal tract, unculturable organisms in the mouth and in the soil, organisms from extreme environments, the diversity of archaea and their phages, comparative genomics and the emergence of pathogens, the spread of genomic islands between clinical and environmental organisms, minimal genomes needed for life, horizontal gene transfer, phenotypic innovation, and patterns and extent of biodiversity.