ABSTRACT
Cyanobacteria are phototrophic prokaryotes with the ability to extract electrons from water and to use the reducing power generated to x carbon dioxide. ey generate oxygen as a waste product from solar-powered water-splitting. Cyanobacteria are an ancient, widespread and diverse group of bacteria that played a crucial role in the history of the biosphere by generating the atmospheric oxygen needed for aerobic heterotrophic life. Cyanobacteria today remain abundant in the oceans and in a wide variety of other habitats, and they
CONTENTS 10.1 Electron Transport Pathways in Cyanobacterial ylakoid Membranes:
Interaction between the Photosynthetic and Respiratory Electron Transport Chains 239
10.2 Nanometre-Scale Organisation of Cyanobacterial Electron Transport Complexes 241 10.3 Submicron-Scale Organisation and Dynamics of Cyanobacterial ylakoid
Membranes 244 10.4 Crowding and Fluidity in the Aqueous Compartments on Either Side of the
Membrane 246 10.5 Examples of Regulation of Membrane Organisation and Electron
Transport: Complex I, Complex II and the Bidirectional Hydrogenase 246 10.6 Length Scales of Electron Transport: Cyanobacterial ylakoids in
Comparison to Other Bioenergetic Membranes 250 Acknowledgements 250 References 251
still generate a signicant proportion of the oxygen that we breathe. e remainder of the oxygen in the atmosphere is generated by the chloroplasts of plants and algae, organelles that are themselves the descendents of a free-living cyanobacterium. Chloroplasts carry out their photosynthetic light reactions in an internal membrane system called the thylakoid membranes, a feature that they have inherited from their cyanobacterial ancestors. Nearly all cyanobacteria contain thylakoid membranes: the single known exception is the atypical cyanobacterium Gloeobacter violaceus, which lacks internal membranes and houses its photosynthetic apparatus in dedicated zones of the cytoplasmic membrane (Rexroth et al., 2011). In all other known cyanobacteria, the photosynthetic apparatus is housed in the thylakoids. In both cyanobacteria and chloroplasts, the thylakoids are a topologically complex system of internal membranes. Connections with the surrounding envelope membrane (the inner envelope in chloroplasts or the cytoplasmic membrane in cyanobacteria) appear absent in chloroplasts (Vothknecht and Westho, 2001) and are ill-dened in cyanobacteria (Liberton et al., 2006; van de Meene et al., 2006; Nevo et al., 2007). e thylakoids serve as a chemiosmotic barrier between the cytoplasm (or the stroma in chloroplasts) and a separate aqueous compartment, the thylakoid lumen. Ultrastructural studies from some cyanobacteria suggest that the entire thylakoid membrane system in the cell may be interconnected, with a continuous membrane surface enclosing a single continuous lumen (Nevo et al., 2007).
