Table 2.
Comparison of the O2 evolution and CO2 assimilation rates of Synechocystis 6803 WT (grown either in the absence or in the presence of 5 mM glucose, Glc) and the PSI deleted ΔAB (grown in the presence of 5 mM glucose) cells. Both the O2 evolution and the CO2 assimilation rates were measured in fresh BG-11 growth medium supplemented with 10 mM NaHCO3 and the corresponding glucose content. As shown in Figure 2, Pobs is the net light-induced O2 evolution rate obtained from the above-zero portion of the O2 evolution traces and Padj is the O2 evolution rate adjusted for respiratory O2 consumption, assuming that the respiration rate in the light is the same as in the dark (positive values for O2 consumption). Since the ΔAB cells differed vastly from the WT cells in their Chl-to-PSII ratios, both the O2 evolution and the CO2 assimilation rates are normalized to the PSII content, utilizing the measured Chl-to-PSII ratios. The rates of corresponding electron fluxes can be obtained by multiplying the O2 evolution rates by 4. The numbers of independent experiments preformed are indicated in parentheses. Detailed experimental conditions are described in Materials and Methods. Despite the high variation in the dark CO2 assimilation rates, the light-minus-dark CO2 assimilation rate is highly statistically significant, as examined by the paired t-test test (one-tailed, p = 0.0003) for 7 independent measurements.
| Parameters measured | WT+Glc | WT-Glc | ΔPSI+Glc |
|---|---|---|---|
| Net O2 evolution rate Pobj (mmol O2·mol Chl−1·s−1) | 68 ± 10 (6) | 82 ± 15 (7) | 56 ± 14 (7) |
| Chl-to-PSII ratio | 490 ± 25 (2) | 518 (1) | 78 ± 4 (2) |
| Net O2 evolution rate Pobj (mol O2·mol PSII−1·s−1) | 34 ± 5 (6) | 42 ± 8 (7) | 4 ± 1 (7) |
| Dark respiration rate R (mol O2·mol PSII−1·s−1) | 5 ± 1 (6) | 4 ± 2 (7) | 6 ± 2 (7) |
| Adjusted O2 evolution rate Padj (mol O2·mol PSII−1·s−1) | 39 ± 5 (6) | 46 ± 8 (7) | 10 ± 3 (7) |
| PSII activity (mol O2·mol PSII−1·s−1) | 66 (1) | — | 110 (1) |
| Dark CO2 assimilation rate (mol CO2·mol PSII−1·s−1) | 1.4 ± 0.7 (3) | 1.4 ± 0.8 (5) | 5 ± 2 (7) |
| Light-minus-dark CO2 assimilation rate (mol CO2·mol PSII−1·s−1) | 16 ± 7 (3) | 34 ± 6 (5) | 2.2 ± 0.9 (7) |