Construction of multiple herbicide resistant ammonia excreting strains of cyanobacterium Nostoc muscorum

Machete resistant (Matr), basalin resistant (Basr), 3(3,4 dichlorophenyl)-1,1-dimethyl urea resistant (DCMUr), atrazine resistant (Atr(r)) and propanil resistant (Prpr) phenotypes Gloeocapsa sp. were contransformed to Nostoc muscorum at high frequency. Spontaneously occurring mutants of the multiple herbicide resistant transformant containing L-methionine-DL-sulfoximine resistant (Msxr), ethylene diamine resistant (Edar) of phosphinothricin resistant (Pptr) 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.