The pattern of acetylene reduction by cyanobacteria grown under alternating light and darkness

Abstract

When N₂-fixing cyanobacteria were grown under alternating 12 h light and 12 h darkness, three patterns of acetylene reduction were observed. All non-heterocystous species reduced acetylene either mainly or exclusively in the dark. This pattern of acetylene reduction may have a role in the protection of nitrogenase from photosynthetically generated O₂. On the other hand all heterocystous species reduced acetylene either mainly in the light or both in the light and the dark, though usually at higher rates in the light.