Dose-response effect of glucose-mediated transcriptional repression of the crtS gene. Cultures of UCD 67-385 were grown until reaching stationary phase and were divided into five aliquots. Glucose was added to each aliquot to a final concentration of 20 (black square), 10 (white triangle), 5 (black inverted triangle) or 1 g/l (white circle); no glucose was added to the control culture (black circle). Subsequently, the amount of glucose remaining in the media was determined (a), along with the relative expression of the crtS gene (b) at 2, 4, 6 and 24 h post-treatment. The error bars correspond to standard deviation (n = 3). The negative values on the y-axis denote decreases relative to the control.