Effect of lysozyme on Synechococcus cell disintegration. Cells were cultivated for 48 hours with either low (0.24 g NaNO3 L-1) or high (1.0 g NaNO3 L-1) initial nitrate concentrations to generate ‘carbohydrate-loaded biomass’ or ‘reference biomass’, respectively. Cell suspensions were concentrated five times (by centrifugation and re-suspension in a smaller volume of the supernatant) and stored at either at 4°C (open circles) or at -20°C (solid circles) for 1 hour prior to incubation with lysozyme (100 mg L-1) at 37°C. Cell disintegration was followed over time by measuring the OD730 after appropriate dilution of small aliquots of the reaction mixture into water. The OD730 is depicted as percentage of the OD730 at the start of the lysozyme treatment. (A) Reference Synechococcus cells. (B) Carbohydrate-loaded Synechococcus cells. h, hours; OD730, optical density at 730 nm.