Photoacoustic detection of oxygen evolution and State 1–State 2 transitions in cyanobacteria

Abstract

Photoacoustic detection of modulated oxygen evolution was obtained from algae in vivo. In the cyanobacterium Nostoc muscorum, during State 1 to State 2 transition, the effective absorption cross-section of PS II measured at 580 and 620 nm, decreased by 10–15% concomitant with an equal increase in the cross-section of Photosystem I. Upon incubation of Nostoc cells with a specific inhibitor of phosphatases (NaF) which blocks dephosphorylation of proteins, State 1 was abolished and only State 2 could be observed. These results suggest that in organisms containing phycobiliproteins as efficient antennae and which are missing both light-harvesting chlorophyll a b protein complex and grana thylakoids the level of protein phosphorylation controls the distribution of excitation energy between the two photosystems.