FIG. 4.

KOCN-dependent CO₂ efflux by cells grown under high-CO₂ conditions. Illuminated wild-type (WT) S. elongatus PCC7942 cells were provided with 1 mM KO¹³CN, and the efflux of ¹³CO₂ was followed by MS over time in the absence or presence of 25 mM NaNO₃ or NaNO₂. Bovine CA was added to the suspension to illustrate that CO₂ was the C_i species arising in the cell suspensions. Also shown are the CO₂ fluxes arising from the cynA and cynS mutants and from Synechocystis sp. strain PCC6803 grown in high-CO₂ concentrations.