Figure 2. O₂ reduction rates of WT and FDP mutants grown at different pH levels.

O₂ reduction rate was recorded in darkness (gray background) and under illumination with actinic white light at an intensity of 500 µmol photons m⁻² s⁻¹ (white background). Pre-cultures were grown in standard BG-11 medium (containing Na₂CO₃ at a final concentration of 0.189 mM) under HC for 3 days at different pH levels. For MIMS experiments, cells were shifted to LC at OD₇₅₀≈0.2 (same pH) and grown for 4 days before measurements. Exceptions were: (i) pH 6 experimental cultures were inoculated from pH 8.2 pre-cultures; and (ii) pH 7.5 pre-culture was shifted to LC in standard BG-11 containing Na₂CO₃ at a final concentration of 0.189 mM or in BG-11 without Na₂CO₃ (dotted line ‘- Na₂CO₃’). The experiment was conducted in three independent biological replicates (except experiment at pH 6 with n = 2 independent biological replicates) and a representative plot is shown. (Figure 2—source data 1). In order to create comparable conditions for MIMS measurements, all cells were supplemented with 1.5 mM NaHCO₃ prior to the measurements.

Figure 2—figure supplement 1. O₂ photoreduction rates of the ∆flv2 and ∆sll0218 mutants grown at LC pH 7.5 and 8.2 with and without Na₂CO₃.

Pre-cultures were grown under HC for 3 days at pH 7.5 or pH 8.2 in BG-11 media with or without Na₂CO₃. For O₂ photoreduction experiments, cells were shifted to LC at OD₇₅₀≈0.2 and grown for 4 days.