Kinetics of blue-green light-induced state transition and fluorescence quenching in the wild-type cyanobacterium Synechocystis PCC 6803 and apcD − and apcF − mutants

State transition and blue-green light-induced fluorescence quenching are two short-term processes in cyanobacteria. The details of their kinetics and the relationship between these processes have not been elucidated. In this work, these two processes were studied in the wild-type cyanobacterium Synechocystis PCC 6803 cells as well as in apcD − and apcF − mutants by monitoring their time-dependent 77 K fluorescence responses to blue-green light (430–540 nm) at a series of intensities ranging from 20–800 µE m −2 s −1 . The lowest light intensity to induce fluorescence quenching in wild-type cells was 160 µE m −2 s −1 under the selected experimental conditions, while state transition took place at the intensities lower than 160 µE m −2 s −1 at a conservative level, but at variable rates. The quenching level increased at intensities higher than 160 µE m −2 s −1 , reaching the maximum level at intensities equal to or higher than 200 µE m −2 s −1 . Fluorescence kinetics indicated that both the length of the induction period and time required to reach the maximum level were functions of light intensity. State transitions as well as fluorescence quenching took place in both wild-type and mutant cells, but might involve different mechanisms.