State transition of <i>Synechocystis</i> PCC 6803 strains.

<p>A, Typical traces of the state transition analysis. Wild type (Wt) and <i>isiA</i>^- (<i>isiA</i>^-) cells in mid-logarithmic growth phase (OD₇₃₀ ∼0.6–0.8) were collected and resuspended to an OD₇₃₀ of 0.6 with fresh BG-11 medium. State transition was analyzed by Chl fluorescence. A far-red light was first applied to the dark-adapted cyanobacterial cultures to fully oxidize PSI, which was followed by a series of saturation flashes to determine the S1 level. An actinic light of 100 µ mol photon m⁻² s⁻¹ was subsequently turned on to induce photosynthesis. The S2 level was then assessed by a saturation pulse before the far-red light was applied again to drive the S2-S1 transition. B and C, Fast fluorescence induction kinetics of the wild type (B) and <i>isiA</i>^- (C) strains at state 1 (S1), state 2 (S2), and state transition level (S1′).