Part I: Biochemistry of acetogenesis and the acetyl-CoA pathway of acetogenic bacteria: Acetogenesis and the acetyl-CoA pathway: current perspectives. Chemiosmotic generation of ATP in acetogens. CO dehydrogenase and the central role of this enzyme in the anaerobic fixation of carbon dioxide. Sodium and proton circuits in the bioenergetics of acetogenic bacteria. Part II: Physiological potentials and ecology of acetogenic bacteria: ecology and diversity of acetogenic bacteria. Growth revisited: resolving new metabolic potentials of acetogens. Acetogensis from carbon dioxide in gastrointestinal ecosystems. O-demythylation and other transformations of aromatic compounds by acetogenic bacteria. Physiological biochemistry of CO metabolizing heteroacetogenic bacteria. Potentials of acetogenic bacteria for industrial processes. Part III: Acetogenic processes in other bacteria groups: autotrophic synthesis of acetyl - CoA in anaerobic microorganisms that are not acetogens. Autotrophic acetyl-CoA biosynthesis by methanogens. CO dehydrogenase of methanogens. Acetate via glycine.