Figure 4. Bifurcation of metabolic fluxes.

(a) Schematic of fluxes into the TCA cycle and glyoxylate shunt following shift from glucose (blue shading) to radiolabelled acetate (red shading). (b) Schematic of fluxes into the TCA cycle and glyoxylate shunt following shift from acetate (red shading) to radiolabelled glucose (blue shading). (c,d) ¹³C-labelling of metabolites in wild-type (c) and Δicl1 Δicl2 (d) M. smegmatis 320 s after shifting glucose to [U-¹³C]-glucose. Comparison of the M+2 isomers of isocitrate, α-ketoglutarate and succinate demonstrate absence of carbon flux through the glyoxylate shunt during growth on glucose. (e) ¹³C-labelling of metabolites in wild-type M. smegmatis 80 s after shifting from acetate to [U-¹³C]-acetate illustrate carbon flux bifurcation to the glyoxylate shunt and the oxidative TCA cycle.