Molecular physiology of sugar catabolism in Lactococcus lactis IL1403

The metabolic characteristics of Lactococcus lactis IL1403 were examined on two different growth media with respect to the physiological response to t wo sugars, glucose and galactose. Analysis of specific metabolic rates indi cated that despite significant variations in the rates of both growth and s ugar consumption, homolactic fermentation was maintained for all cultures d ue to the low concentration of either pyruvate-formate lyase or alcohol deh ydrogenase. When the ionophore monensin was added to the medium, Bur throug h glycolysis was not increased, suggesting a catabolic flux limitation, whi ch, with the low intracellular concentrations of glycolytic intermediates a nd high in vivo glycolytic enzyme capacities, may be at the level of sugar transport. To assess transcription, a novel DNA macroarray technology emplo yed RNA labeled in vitro with digoxigenin and detection of hybrids with an alkaline phosphatase-antidigoxigenin conjugate. This method showed that sev eral genes of glycolysis were expressed to higher levels on glucose and tha t the genes of the mixed-acid pathway were expressed to higher Levels on ga lactose, When rates of enzyme synthesis are compared to transcript concentr ations, it can be deduced that some translational regulation occurs with th reefold-higher translational efficiency in cells grown on glucose.