Effects of light and chloramphenicol stress on incorporation of nitrogen into cyanophycin in Synechocystis sp. strain PCC 6308

1H NMR spectroscopy was used to compare the uptake of nitrogen into cyanobacterial cyanophycin from two sources: from the breakdown of intracellular proteins and amino acids, and directly from the external growth medium. Cells grown initially in medium containing 14N-nitrate were transferred to 15N-nitrate medium in the presence of chloramphenicol in both low (4 μE m−2 s−1) and normal (100 μE m−2 s−1) light, and in low light alone. Cyanophycin was separated from cells and analyzed by 1H NMR spectroscopy. Cyanophycin is synthesized both from 14N (degradation of cellular proteins) and from 15N in the medium, the latter at a faster rate and to a greater extent under all conditions. SDS-PAGE showed that cyanophycin synthesis takes place by addition of monomers to already synthesized polymer.