Construction of multiple herbicide resistant ammonia excreting strains of cyanobacteriumNostoc muscorum

Summary Machete resistant (Mat^r), basalin resistant (Bas^r), 3(3,4 dichlorophenyl)-1,1-dimethyl urea resistant (DCMU^r), atrazine resistant (Atr^r) and propanil resistant (Prp^r) phenotypes ofGloeocapsa sp. were cotransformed toNostocmuscorum at high frequency. Spontaneously occurring mutants of the multiple herbicide resistant transformant containing L-methionine-DL-sulfoximine resistant (Msx^r), ethylene diamine resistant (Eda^r), or phosphinothricin resistant (Ppt^r) glutamine synthetase (GS) showed extracellular liberation of ammonia resulting from fixation of N₂ under photosynthetic conditions. Results suggest a definite role of GS activity in regulation of extracellular ammonia.