1. General considerations -- 2. Mineral cycles -- 3. The water column -- 4. Biogeochemical cycling in soils -- 5. Aquatic sediments -- 6. Microbial mats and stratified water columns -- 7. Symbiotic systems -- 8. Biogeochemistry and extreme environments -- 9. Microbial biogeochemical cycling and the atmosphere --10. Origins and evolution of biogeochemical cycles --App. 1. Thermodynamics and calculation of energy yields of metabolic processes