CO2 Acquisition, Concentration and Fixation in Cyanobacteria and Algae

摘要: Aquatic photosynthetic organisms face a number of unique problems with regard to the supply CO2 for photosynthesis. These stem largely from physical chemistry water phase in which they live, where diffusion C1 species is slow and can exists as both HCO3− depending on pH medium. Given constraints, solutions have evolved optimize fixation algae cyanobacteria. The two chief strategies that are apparent development CO2-concentrating mechanisms based active uptake evolution more efficient forms Rubisco able fix at limiting levels CO2. This chapter examines aspects co-evolution Particular emphasis placed what known about mechanism operation carbon concentrating (CCMs) cyanobacteria green microalgae. In cyanobacteria, multiple transporters drive CCM plasma membrane. energized by ATP NADPH production, NAD(P)H dehydrogenase complexes playing critical role. A pool accumulated within cell this used Rubisco-containing carboxysome generate localized micro-environment. Carboxysomal carbonic anhydrase crucial generation process. For microalgae, transport occurs membrane chloroplast envelope. HCO3 stroma, aid energy, elevate around Rubisco. primarily pyrenoid. part conversion appears be thylakoid lumen anhydrase, may use lumenal protons inducible nature algae, increasing its affinity forexternal when cells grown conditions. non-green presence significant activity correlated pyrenoids single chloroplasts cells. possible diversity among highlighting variation operations compared models developed Considerable work remains done identify specific mechanismsin algae.