Figure 1.

Nutrient supplementation allows growth to higher cell density with light as the sole limiting substrate. (A) Cell density (OD730 converted to g DW L⁻¹ as described in methods) over time measured for cultures of PCC7002 grown in shake flasks in 1% CO₂ and 37°C in Media A with no supplement (red), supplemented with 110 mM NaNO₃ (blue), supplemented with 110 mM NaNO3 and 31 mM KH₂PO₄ in a fed batch scheme as described in the methods (purple), or supplemented with 110 mM NaNO3, 31 mM KH2PO4 in a fed batch scheme, and 1.1 mM FeCl₃ (green). Error bars are standard error of 3 biological replicates for red, blue, and purple or 2 biological replicates for green. (B) Average absorbance scans normalized to OD730 of samples from the flasks described in (A) are shown over time to show loss of pigmentation in nutrient deplete media and pigment persistence in nutrient sufficient media. Absorbance profiles over time are offset on the y-axis for clarity (baselines in black).