Nitrogen deprivation strongly affects Photosystem II but not phycoerythrinlevel in the divinyl-chlorophyll b-containing cyanobacterium Prochlorococcus marinus

Effects of nitrogen limitation on Photosystem II (PSII) activities and on p hycoerythrin were studied in batch cultures of the marine oxyphotobacterium Prochlorococcus marinus. Dramatic decreases in photochemical quantum yield s (F-V/F-M), the amplitude of thermoluminescence (TL) B-band, and the rate of QA reoxidation were observed within 12 h of growth in nitrogen-limited c onditions. The decline in F-V/F-M paralleled changes in the TL B-band ampli tude, indicative of losses in PSII activities and formation of non-function al PSII centers. These changes were accompanied by a continuous reduction i n D1 protein content. In contrast, nitrogen deprivation did not cause any s ignificant reduction in phycoerythrin content. Our results refute phycoeryt hrin as a nitrogen storage complex in Prochlorococcus. Regulation of phycoe rythrin gene expression in Prochlorococcus is different from that in typica l phycobilisome-containing cyanobacteria and eukaryotic algae investigated so far. (C) 2001 Elsevier Science B.V. All rights reserved.