StreptomycescoelicolorA3(2) belongs to the high-GC gram-positive actinobacteria and is characterized by undergoing a complex life-cycle, includingvegetative hyphae, aerial hyphae and spores. As an obligate aerobeS. coelicolorusesaerobic respiration for growth, butstudiesin this area arelimited. Theaerobic respiratorychain terminates with multiple cytochrome oxidases. Despite requiring oxygen for growth, the genome of S. coelicolor habours three operons encoding respiratory nitrate reductases (Nars). Thus,S. coelicolor is able to respire with nitrate when oxygen is not available. The regulatory switch between aerobic respiration and nitrate respiration during the lifecycleis the subject of this dissertation. This work reveals new aspects regarding aerobic respiration, identifying a new spore-specific oxidase.Moreover,all three Nars were analyzed in the context of the developmental programand a putative link between Nar1 and components of the aerobic respiratory chain in spores was established.