Cytochrome bd Oxidase Has an Important Role in Sustaining Growth and Development of Streptomyces coelicolor A3(2) under Oxygen-Limiting Conditions

Abstract

Respiring with oxygen is an efficient means of conserving energy in biological systems. The spore-forming, filamentous actinobacterium Streptomyces coelicolor grows only aerobically, synthesizing two enzyme complexes for O 2 reduction, the cytochrome bcc-aa 3 cytochrome oxidase supercomplex and the cytochrome bd oxidase. We show in this study that the bacterium can survive with either of these respiratory pathways to oxygen. Immunological studies indicate that the bcc-aa 3 oxidase is the main oxidase present in spores, but the bd oxidase compensates if the bcc-aa 3 oxidase is inactivated. Both oxidases are active in mycelia. Growth conditions were identified, revealing that cytochrome bd oxidase is essential for aerial hypha formation and sporulation, and this was linked to an important role of the enzyme under oxygen-limiting conditions.