This volume is a comprehensive treatement of the genetics and molecular biology of anaerobic bacteria. Anaerobes share two essential characteristics: an extreme sensitivity to molecular oxygen and a capacity to produce energy and perform biosyntheses in its absence. Anaerobes have emerged in recent years as exceptionally interesting and important organisms with respect to their ecology, their role in diseases and in biotransforamtion, and in the search for alternative renewable sources of energy. The application of modern methods in genetics and molecular biology over the past 15 years has revolutionized understanding of the biology and evolution of these prokaryotes.