Carbohydrate cycling in micro-organisms: what can (13)C-NMR tell us?
The extension of (13)C-nuclear magnetic resonance (NMR) techniques to study cellular metabolism over recent years has provided valuable data supporting the occurrence, diversity and extent of carbon cycling in the carbohydrate metabolism of micro-organisms. The occurrence of such cycles, resulting from the simultaneous operation of different and sometimes opposite individual steps, is inherently related to the network organisation of cellular metabolism. These cycles are tentatively classified here as 'reversibility', 'metabolic' and 'substrate' cycles on the basis of their balance in carbon and cofactors. Current hypotheses concerning the physiological relevance of carbohydrate cycles are discussed in light of the (13)C-NMR data. They most likely represent system-level mechanisms for coherent and timely partitioning of carbon resources to fit with the various biosynthetic, energetic or redox needs of cells and/or additional strategies in the adaptive capacity of micro-organisms to face variation in environmental conditions.
Portais
Jean-Charles
JC
Laboratoire de Génie Cellulaire, UMR CNRS 6022, Faculté des Sciences, Université de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens Cedex, France. jean-charles.portais@insa-tlse.fr
Delort
Anne-Marie
AM
D016948:Azotobacter vinelandii / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism; D001711:Biotransformation / Q000502:physiology; D050260:Carbohydrate Metabolism; D002247:Carbon Isotopes; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008954:Models, Biological; D010427:Pentose Phosphate Pathway; D011549:Pseudomonas / Q000378:metabolism; D012230:Rhizobiaceae / Q000378:metabolism; D015219:Substrate Cycling
D002247:Carbon Isotopes