Figure 6.

Schematic representation of GlmS regulation by GlmR, UDP-GlcNAc and YvcJ in B. subtilis depending on growth conditions. (A) When B. subtilis is grown in the presence of non-glycolytic carbon sources like intermediates of Krebs cycle, the glmR mutant cells have an abnormal rod-shape then lyse and the deletion of glmR is lethal¹⁹. In such conditions, stimulation of GlmS by GlmR is essential for a sufficient production of UDP-GlcNAc and thus for a correct PG synthesis; YvcJ is free. (B) When B. subtilis is grown in the presence of glycolytic carbon sources like glucose, the glmR mutant cells have a normal rod-shape and deletion of glmR has no effect¹⁹. The intracellular concentration of F6P is high, 16-fold higher in comparison to growth on malate²⁷. Consequently, intracellular concentration of UDP-GlcNAc is probably high and therefore stimulation of GlmS by GlmR is not essential for correct synthesis of PG. In such conditions, GlmR is bound to UDP-GlcNAc and GlmS activity is not stimulated to avoid an excess of UDP-GlcNAc synthesis. In addition, GlmR bound to UDP-GlcNAc interacts with YvcJ to stabilize it and potentially stimulate its activity. In parallel, GlcN6P binds to glmS ribozyme and regulates GlmS intracellular concentration.