This is a book about the natural history of oxygen-free environments and their microbial inhabitants. Life originated in the pre-oxic world, and anoxic conditions still persist in many places on Earth such as lake sediments, the guts of ruminants, and the deep waters of some marine basins. Drawing on evidence from a variety of scientific disciplines, the authors describe the forces known to shape the structure, function, heterogeneity, and evolution of anaerobic communities.

The approach taken is all-embracing: from the origin and maintenance of anoxic habitats throughout Earth's history, through the origin of prokaryotes, eukaryotes, and eukaryotic organelles, to the development of microbial communities. Particular emphasis is placed on exploring the energy-yielding pathways which have evolved in anaerobic micro-organisms and how this metabolic repertoire dictates the syntrophic and competitive interactions which largely determine anaerobic microbial community structure. Interactions with the oxic world are explored in the last chapter.

The ecological and evolutionary significance of the arrival of oxygen in the Proterozoic is discussed in detail, especially as it eventually led to the possibility of long food chains. This volume synthesizes major areas of microbial ecology and will interest students and researchers working in this and related fields.