Figure 1From: Global insights into energetic and metabolic networks in Rhodobacter sphaeroidesCategorization of growth substrates based on NADPH demand and requirement for PntAB under photosynthetic conditions. (A) R. sphaeroides growth on glucose via the Entner-Doudoroff pathway includes the NADPH-generating glucose-6-phosphate (G6P) dehydrogenase enzyme (Zwf), which supports normal photosynthetic growth even in the absence of PntAB. (B) R. sphaeroides growth on acetate is predicted to occur via the ethylmalonyl-CoA (EM-CoA) pathway, involving oxidation of 2 molecules of NADPH per 3 molecules of acetyl-CoA (A-CoA) consumed [59]. Note that a third molecule of A-CoA used up in later steps of the EM-CoA pathway is not depicted in this illustration. (C) During photosynthetic growth on substrates that do not directly produce NADPH (e.g. succinate), PntAB is required. In some cases, after a long lag period, cells adapt and grow photosynthetically albeit at a slower growth rate (17.2 ± 0.56 hrs compared to 7.53 ± 0.56 hrs for wild type cells). Abbreviations: AA-CoA – acetoacetyl-CoA; 3HB-CoA – 3-hydroxy butyryl-CoA; Cr-CoA – crotonyl-CoA; 6PGL – phosphoglucono-δ-lactone.Back to article page