Fig. 6: Changes in the levels of 2-OG, L-glutamate, and ppGpp in ∆Rel cells during light-to-dark transition.

S. elongatus PCC 7942 wild type (■) and ∆Rel (□) cells were cultured for 72 h with 100 μmol photons m⁻² s⁻¹ in the presence of 17 mM sodium nitrate and 1% (v/v) CO₂. Next, the cells were transferred to the dark and cultured for 120 min, wherein 0 min was considered the start point to the transition to dark; finally, the cells were again transferred to light conditions. The cells were harvested at 0, 15, 30, 60, 90, and 120 min and every 30 min before and after dark transitions. 2-OG, L-glutamate, and ppGpp levels were measured using CE-TOFMS analysis. All data are presented as mean ± SD (n = 3 independent biological experiments). Statistical significance between each sampling point of wild-type and ∆Rel cells was determined using Student’s t test (**p < 0.01, *p < 0.05).