Catalyzes the ATP-dependent biosynthesis of glutamine from glutamate and ammonia. ATP + L-glutamate + NH4(+) = ADP + H(+) + L-glutamine + phosphate Transferase activity is inhibited by NH(4)Cl. Homooctamer and homotetramer. Up-regulated by the nitrogen regulatory protein NtrC. Two forms of glutamine synthetase (GSI and GSII) can be found in this nitrogen fixing bacteria, GSI is a typical prokaryotic glutamine synthetase whereas GSII is similar to the eukaryotic enzyme. Belongs to the glutamine synthetase family.