This review describes the organic inventory in the wastes in German facilities, the microbial processes, such as aerobic and anaerobic processes, sulfate reduction, pH and ionic strength ranges and chaotropic effects on microbial activity. The microbial effects are discussed for resident and introduced microorganisms and the environmental conditions. The microbial population above the Gorleben salt dome and their effects of microorganisms on the retention of technetium and selenium are shown.