Environmental stimuli and regulatory factors affecting the expression of the glutamic acid decarboxylase system in Escherichia coli

In enterobacteria the gad system, which includes genes encoding PLP-dependent glutamic acid decarboxylases, is required to overcome the acid stress. Herein, we provide evidence that the gad system is strongly induced also during anaerobic growth and suggest the possible involvement in gad trasncriptional control of two AraC-like proteins. Similarly to other decarboxylation/antiport systems, the gad system would confer a unique growth advantage under anaerobic conditions by generating an alectrogenic potential which can be used to fuel ATP synthesis.