Fig. 3

PHB production of Synechocystis sp. PCC 6803 and B12 cells. A, B Nile Red fluorescence normalised on OD₇₅₀, used as proxy for PHB production, after 2, 4 and 7 days from the beginning of the experiment. Synechocystis sp. strains were grown in BG-11 medium N-replete or N-free, in low-light conditions at 35 μmol photons m⁻² s⁻¹ (A) and in high-light conditions at 300 μmol photons m⁻² s.⁻¹ (B). C Confocal images of a Synechocystis sp. B12 cell grown in N starvation for 7 days, stained with Nile Red highlighting PHB granules. Red indicates chlorophyll autofluorescence, green for Nile Red-stained PHB granules. Scale bar: 3 µm. D Quantification of PHB as percentage of cell dry weight. Data indicate the average (± SD) of at least three biological replicates. * indicates p < 0.05, ** p < 0.01, *** p < 0.001 and **** p < 0.0001 (for complete statistical output, see Table S1)