Energy deprivation and guanosine 5'-diphosphate 3'-diphosphate synthesis in cyanobacteria

A reduction in the incident light intensity has been used to elicit guanosine 5'-diphosphate 3'-diphosphate accumulation in cyanobacteria. Inhibitors of photophosphorylation, 2,4-dinitrophenol, and carbonyl cyanide-m-chlorophenyl hydrazone elicited accumulation in three species of cyanobacteria when they were grown on dinitrogen or nitrate, but not in cultures grown on ammonium or glutamine. Accumulation of guanosine 5'-diphosphate 3'-diphosphate also preceded a substantial reduction of the purine nucleoside triphosphate pools. This accumulation of guanosine 5'-diphosphate 3'-diphosphate is therefore not primarily dependent upon reduced ATP concentration or proton gradient potential, but rather upon the source of combined nitrogen. In this respect, incident light step down is not comparable with nutritional step-down procedures in heterotrophic bacteria.