Fig. 2

Comparative physiological characterization of the Synechocystis 6803 WT and ΔssaA mutant strain and phenotype studies of the mutant strain. Cultures were grown under continuous white light at an irradiance of 80 μmol photons m⁻² s⁻¹, at 30 °C, in nitrogen-depleted medium for 189 h before recovery was initiated by adding nitrogen. a Photograph of cultures of Synechocystis 6803WT and ΔssaA mutant strain during recovery from nitrogen starvation, t = 22 h + N. Cultures were adjusted so that their cell densities were the same (as estimated by the OD₇₅₀), transferred to 1-cm cuvettes, and photographed with illumination from behind. b Chlorophyll content of Synechocystis 6803 WT and ΔssaA measured after cultivation in nitrogen deficiency for 189 h (t = 0 h + N) and at recovery time points t = 1 h, t = 4 h, t = 22 h and t = 48 h (+N). The illustrated data represent the mean from three independent biological replicates and the standard deviation was calculated. c Details of whole cell absorbance spectra of Synechocystis 6803 WT and ΔssaA strains are shown for the time point t = 0 h + N, which corresponds to 189 h under nitrogen deficiency (−N) and for the time points t = 4, t = 22, t = 48 and t = 144 h after nitrogen addition (+N). The spectra were normalized at 750 nm. C: carotenoids; PC: phycocyanine; Chl: chlorophyll a