FIG. 2.

Photoinhibition analyses of the Synechocystis sp. strain PCC 6803 GT and the ΔQ quadruple mutant. Cells at a Chl a concentration of 20 μg ml⁻¹ were treated with high light (1,200 μE m⁻² s⁻¹) at 29°C over a period of 6 hours. Oxygen evolution of whole cells was assessed for the Synechocystis sp. strain PCC 6803 GT and the ΔQ quadruple mutant strains in the presence or absence of 100 μg ml⁻¹ lincomycin at the indicated time points in the presence of 2 mM DCBQ and 1 mM K₃Fe(CN) using a Hansatech DW2 oxygen electrode (Hansatech Instruments Ltd., United Kingdom). Oxygen evolution rates (in μmol oxygen per mg of Chl a per h) were normalized (value at t = 0 was 100%) and plotted as a function of time. Error bars represent standard deviation from the means of three measurements. The initial, absolute rates of oxygen evolution for the respective strains were as follows: 324 (ΔQ without Linc), 316 (GT without Linc), and 350 (GT +Linc) (all in μmol oxygen per mg of Chl a per h).