Fig. 3
a Pathways for fructose, glucose and gluconate assimilation in C. salexigens. The proposed pathways are based on previous in silico and phylogenetic studies comparing C. salexigens with P. putida and other closely related species. The two proposed fructose assimilation pathways, are supported by 13C-, and 31P-NMR results and RT-PCR and heterologous expression studies from the present work. Names of enzymes and transporters are shown in rectangles and ellipses, respectively. Enzyme activities confirmed by 31P-NMR and included in RT-PCR expression studies are shown in blue boxes; ORFs from RT-PCR studies not assayed/not detected by 31P-NMR assays are shown in green boxes. The rest of proposed enzymes and transporters are shown in colourless boxes. b Gene clusters and operons related to fructose and glucose assimilation pathways in C. salexigens. Above each ORF, the name of the most plausible functional assignment is shown. ORFs included in RT-PCR studies are in colourless rectangles. 1Pfk: 1-phosphofructokinase; Aep: aldose-1-epimerase; Ald: fructose-1,6-bisphosphate aldolase; Eda: 2-keto-3-deoxy-6-phosphogluconate aldolase; Edd: 6-phosphogluconate dehydratase; Frk: fructokinase; Gapdh: glyceraldehyde-3-phosphate dehydrogenase; Gcd: glucose dehydrogenase; Glcnl: gluconolactonase; Glk: glucokinase; GntP: gluconate transporter; KguD: 6-phosphogluconate dehydrogenase, KguK: 2-ketogluconate kinase; 2-keto-6-phosphogluconate reductase; KguT: 2-ketogluconate transporter; Pgi: phosphoglucose isomerase; Pgl: 6-phosphogluconolactonase; Pgk: phosphoglycerate kinase; Pts: phosphotransferase transport system (fructose specific); Tpa: tagatose-6-phosphate aldolase; Zwf, glucose-6-phosphate dehydrogenase. 1Sugar facilitators or ABC transporters (genes not assigned yet). 2The two remaining ORFs that are still assigned to PfkB on the basis of similarity of their predicted sequences to authentic phosphofructokinases, but without any further experimental evidence. 3fruBKA operon. The following ORFs bear a wide assignment based on automated annotation: a, LacI family transcriptional regulator; b, short chain dehydrogenase/reductase; c, putative fructose transport system kinase; d, mannitol dehydrogenase-like protein; e, aldo/keto reductase; f, NAD+-binding d-isomer specific 2-hydroxyacid dehydrogenase