Fig. 7: Two distinct pathways for D-ribulose utilisation in attaching and effacing pathogens.

Schematic model illustrating; a the Rbl system of C. rodentium that is specifically regulated in response to D-ribulose, required for its uptake (via the RblABCD ABC transporter) and essential for its utilisation as a carbon source (via the RblK D-ribulokinase). The regulatory effector activating the system is unknown but is dependent on D-ribulose metabolism. b the Aau system of EHEC that is regulated exclusively in response to ʟ-arabinose and mediates low affinity transport (dashed arrow) but displays dramatically higher affinity (bold dashed arrow) for D-ribulose. EHEC cannot utilise D-ribulose as a sole carbon source. However, in the presence of ʟ-arabinose, AraC activates expression of Aau and the canonical ʟ-arabinose utilisation machinery, leading to D-ribulose uptake (via the AauABCD ABC transporter) and catabolism (via the D-ribulokinase activity of AraB).