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Abstract
The synthesis of metabolic enzymes for poor carbon sources are repressed in the presence of glucose. It was investigated whether Escherichia coli cultured in various concentrations of glucose and sucrose would undergo β -galactosidase repression from the lac operon and to what extent. Cells were initially grown in 0.2% glycerol prior to the addition of one of the following nutrients: 0.08% glucose, 0.06% glucose, 0.05% glucose, 0.045% glucose, 0.08% sucrose, 0.06% sucrose, 0.05% sucrose and 0.045% sucrose. The data acquired indicates that glucose is more effective at catabolite repression than equal concentrations of sucrose as seen by a slowed induction rate compared to the glycerol control. No significant differences in repression were observed within the tested concentration range for either sugar suggesting that either the assay was not sensitive enough to differentiate between subtle changes in enzyme activity or that it may function in a discontinuous manner instead of a continuous trend, with all tested concentrations falling above a certain threshold value.