13C Nuclear Magnetic Resonance Study of Biosynthesis of Glucosylglycerol by a Cyanobacterium under Osmotic Stress

Summary: 13C nuclear magnetic resonance spectroscopy was used to study the biosynthesis and turnover of O-α-Dglucopyranosyl-(1→2)-glycerol (glucosylglycerol) in the marine cyanobacterium Synechococcus N100 during osmotic shock. There was a rapid increase in the level of this heteroside following hyperosmotic shock, with most of the solute being synthesized from extracellular carbon via photosynthetic CO2 fixation. However, changes in the 13C labelling patterns during the time course of the response suggested that up to 10% of the newly synthesized material may be derived from intracellular carbon. No increase in glucosylglycerol was observed when cells were subjected to hyperosmotic shock in the dark. These experiments indicated that a good yield of highly 13C-enriched glucosylglycerol, which could serve as a source of labelled glucose and glycerol, could be obtained simply and quickly by subjecting this cyanobacterium to hyperosmotic stress in the presence of 90% 13C-enriched bicarbonate.