Membrane‐Bound Protein Complexes for Photosynthesis and Respiration in Cyanobacteria

Abstract

Cyanobacteria are the evolutionarily oldest organisms with the capability of evolving oxygen, giving rise to the present day atmosphere. These prokaryotic microorganisms have the unique ability to perform oxygenic photosynthesis and respiration in the same cellular compartment. Some cyanobacteria can also fix atmospheric nitrogen alongside oxygenic photosynthesis and respiration. The redox components of these electron transport pathways are known to intersect in cyanobacteria. Majority of the energy‐intensive processes occur in specialised membranes known as thylakoids. The coexistence of such remarkably complex metabolic pathways in a single cyanobacterial cell provides them with the potential to thrive in a wide variety of ecosystems. This metabolic complexity has sparked significant interest towards cyanobacterial research for the production of various high‐value compounds with applications in the food, feed and fuel industry. Key Concepts Cyanobacteria are the only prokaryotic microorganisms with the extraordinary capability of converting sunlight to chemical energy and evolving molecular oxygen as a byproduct. Complex metabolic processes such as photosynthesis and respiration coexist and predominantly occur in highly specialised thylakoid membranes. The photosynthetic and respiratory electron transport chain shares several components between these processes, a situation unique to oxygenic photosynthetic organisms. In ambient light conditions, photosynthetic electron transport chain has a much higher capacity for ATP synthesis than respiration.