Fig. 13

Speculated regulatory mechanism of dissolved oxygen tension in B. subtilis cells. When the DO concentration decreased (left) ResE can activate ResD, a regulatory protein that can regulate the expression of genes fnr, narK, J, I, H, G and so on. Global regulator FNR was speculated to be responsible for the down-regulated ykgB and up-regulated alsS, which lead to decreased flux through PP pathway, lower riboflavin production and increased flux through glycolysis and overflow metabolism. Nitrate accepted more electrons as genes narK, J, I, H, G were activated. When the DO concentration was high enough (right) ResE will dephosphorylate ResD and enough oxygen molecules can maintain the normal operation of electron transport chain