2.4. Cells preparation for nutrient modification
Cells of Synechocystis wild type, OE strains phaAB, phaEC and phaABEC were grown in 50 mL of BG11 medium (complete nutrients) until late log phase (OD730 1.2). The cultures were harvested by centrifugation at 2790 g, 15 min, room temperature and the cell pellets were washed twice with desired medium prior to the nitrogen deprivation experiment. For nitrogen deprived condition, washed cells were transferred to fresh BG110 medium (BG11 medium lacking NaNO3) in which ferric ammonium citrate and Co (NO3)2 6H2O were replaced with equimolar concentrations of ferric citrate and CoCl2 6H2O, respectively. Phosphorus deprived condition was achieved by replacing K2HPO4 in BG11 medium with equimolar concentration of KCl. The mixotrophic condition was obtained by supplementing acetate at a final concentration of 0.4% (w/v) to the medium without changing any other culture parameters.