Fig. 2: Delayed cessation of CO₂ incorporation by Δxpk after light-to-dark switch.

a, Three WT and the three Δxpk cultures were grown in BG11 medium containing 50 mM NaHCO₃ under 12-h L/D cycles until the OD₇₃₀ reached 1 (top). Then, during hours 5–6 in the light period, both cultures were refreshed with BG11 then supplied with 2 mM NaH¹⁴CO₃, as time 0, under 50 μmol m⁻² s⁻¹ light. The light was switched off 10 min later. The ¹⁴C incorporation was analyzed for samples collected at 5, 10, 11, 13, 15 and 20 min. The ¹⁴C incorporation % (y axis) was calculated by ¹⁴C_cell / (¹⁴C_cell + ¹⁴C_medium) (n = 3 biological repeats, mean ± s.e.m.). Under the same experimental conditions as above, WT and Δxpk cultures were supplied with 2 mM unlabeled NaHCO₃ (bottom). Equal volumes of culture samples from each time point were collected and the ATP concentration was determined by a luminescence-based assay, as described in Methods (n = 3 biological repeats, mean ± s.e.m.). b, WT and Δxpk cultures were grown under 10-min L/D cycles then supplied with 10 mM NaH¹⁴CO₃ at the end of the night, as time 0. c, Same as b, except for growing under 250-min L/D cycles.

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