Simplified model for the interaction of L-carnitine production pathway with central metabolism of E. coli strains. The main pathways involved (and their codifying genes) are shown. Central metabolism: AceK (aceK), isocitrate dehydrogenase phosphatase/kinase; ACK (ackA), acetate kinase; ACS (acs), acetyl-CoA synthetase; ICDH (icd), isocitrate dehydrogenase; ICL (aceA), isocitrate lyase; ICLR (iclR), repressor of the glyoxylate shunt; MDH (maeB), malate dehydrogenase; ME (sfcA), malic enzyme; PEPCK (pckA), phosphoenolpyruvate carboxykinase; PFL (pflB), pyruvate:formate lyase; PTA (pta), phosphotransacetylase; FumR (frdABCD), fumarate reductase. L(-)-carnitine pathway: CaiB: carnitine:CoA transferase; CaiC: betaine:CoA ligase; CaiD, enoyl-CoA hydratase; CaiT, carnitine/crotonobetaine/γ-butyrobetaine transporter. Pathway regulators are shown in red. Steps which are not functional under anaerobiosis are shown with grey arrows. Adapted from .