Fig 2.

Growth and extracellular lactate formation in engineered strains of Synechocystis sp. PCC6803, carrying a heterologous lactate dehydrogenase gene (ldh), cultured in continuous light (A) or in a light/dark cycle (B). Cells were grown in BG-11 medium supplemented with 50 mM NaHCO₃. Filled symbols represent the OD₇₃₀s; open symbols represent the lactate concentrations. SAA013, the strain with integrated E. coli ldh, is represented by diamonds (assaying for d-lactate); SAA015, the strain with integrated B. subtilis ldh, is represented by squares (assaying for l-lactate). Values are the averages for biological replicates; error bars indicate the standard deviations (n = 3); if error bars are not visible, they are smaller than the data point symbol. Cultures were grown under continuous white-light illumination (30 μE/m²/s; A) or under a light/dark cycle of 16 h of light (30 μE/m²/s) and 8 h of darkness (B). Gray-shaded areas represent the dark periods. SAA013 did not show l-lactate production, and SAA015 did not show d-lactate (data not shown).