Nitrogen limitation and recovery in the cyanobacterium Aphanocapsa 6308

Abstract

The effects of nitrogen limitation and recovery on nitrogen-containing macromolecules were followed in the cyanobacterium Aphanocapsa 6308. Removal of nitrogen from growth media triggers the degradation of the endogenous nitrogen reserves phycocyanin and cyanophycin granule polypeptide in the cyanobacterium Aphanocapsa 6308. Nitrogen recovery involves immediate synthesis of cyanophycin granule polypeptide with peak levels of 5–12% of cell dry weight found 8–12 h after a utilizable nitrogen source is added. A rapid decrease in cyanophycin granule polypeptide level then occurs and the level remains low even in light-limited stationary growth with all nitrogen sources tested except nitrate and ammonia. Protein and phycocyanin recoveries began 3 h after a utilizable nitrogen source was added. Data suggest continuous activity of the enzyme system synthesizing cyanophycin granule polypeptide in nitrogen-limited cells, but synthesis of a degrading system only after nitrogen recovery begins.