Analysis of sugar metabolism in an EPS producing Lactococcus lactis by P-31 NMR

Sugar metabolism and exopolysaccharide (EPS) production was analysed in Lac tococcus lactis by in vivo P-31 NMR. Transient production of several sugar phosphates, transient depletion of intracellular phosphate, transient produ ction of ATP and UTP, transient acidification of the medium and alkalinisat ion of the cytoplasm could be observed in a period of 20 min upon energisat ion by the addition of glucose. EPS and non-EPS producing variants showed s imilar NMR spectra, the exception being two pH-dependent resonances observe d in the former. They were already observed before addition of glucose and their response to glucose incubation reflected exposure to the medium. They are presumably phosphorylated poly- or oligosaccharides being loosely adhe red to cell walls. By freezing and perchloric acid extraction of the cell m aterial, different types of phosphorylated compounds could be recognised in the NMR spectra such as fructose-1-6-diphosphate, nucleotides (like ADP, A TP, UTP and TDP) and several nucleotide sugars. The ongoing work is focused on identifying the unknown peaks and quantifying the differences between w ild-type cells and the EPS producing variant. (C) 2000 Elsevier Science B.V . All rights reserved.