Sustained photoproduction of ammonia from dinitrogen and water by the nitrogen-fixing Cyanobacterium anabaena sp. strain ATCC 33047

摘要

Conditions have been developed that lengthen the time during which photosynthetic dinitrogen fixation byfilaments of the cyanobacterium Anabaena sp. strain ATCC 33047 proceeds freely, whereas the subsequentconversion of ammonia into organic nitrogen remains blocked, with the resulting ammonia released to the outermedium. When L-methionine-DL-sulfoximine was added every 20 h, maximal rates of ammonia production (25to 30 ,umol/mg of chlorophyll per h) were maintained for about 50 h. After this time, ammonia productionceased due to a deficiency of glutamine and other nitrogenous compounds in the filaments, conditions whichfinally led to cell lysis. The effective ammonia production period could be further extended to about 7 days byadding a small amount of glutamine at the end of a 40-h production period or by allowing the cells to recover for8 h in the absence of L-methionine-DL-sulfoximine after every 40-h period in the presence of the inhibitor. Amore prolonged steady production of ammonia, lasting for longer than 2 weeks, was achieved by alternatingtreatments with the glutamine synthetase inhibitors L-methionine-DL-sulfoximine and phosphinothricin,provided that 8-h recovery periods in the absence of either compound were also alternated throughout. Thebiochemically manipulated cyanobacterial filaments thus represent a system that is relatively stable with timefor the conversion of light energy into chemical energy, with the net generation of a valuable fuel and fertilizerthrough the photoreduction of dinitrogen to ammonia.