Ammonium-nitrogen partitioning under different balances of nitrogen and carbon in the cyanobacterium Anabaena cylindrica.

Abstract

The composition of free amino acids in nitrogen-fixing cells of Anabaena cylindrica was changed by varying the ratio of N2 to CO2 in the gas phase of the medium. Glutamate, aspartate and alanine were the major components in the free amino acid pool of cells incubated in the light and with air supplemented with 0.5% CO2. When the cells were bubbled with pure N2, cellular glutamine, citrulline and arginine increased while glutamate decreased. Adding NH+4 in the dark stimulated the increase of glutamine but not citrulline. Light was required for the rapid synthesis and accumulation of citrulline. Carbonylcyanide metachlorophenylhydrazone (CCCP), which inhibits ATP synthesis, suppressed the NH+4- timulated increase in citrulline in the light. It is concluded that the balance in nitrogen and carbon supply and cellular ATP level determined the metabolism of glutamine, which changed the composition of the cellular free amino acid.