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Catabolite Repression and Induction of Betagalactosidase Synthesis

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Apart from induction, synthesis rate is determined by catabolite repression, whereby it slows down the synthesis of beta-galactosidase especially in the presence of a better carbon (and energy) source, such as glucose. In this experiment, Escherichia coli (E. coli) is used as the bacteria to induce synthesis of enzyme β-galactosidase. The results support lactose metabolism by newly synthesised beta-galactosidase and also, quantitatively, IPTG is a more effective inducer of beta-galactosidase synthesis than lactose.In order to regulate the gene expression levels in a cell, there are certain mechanisms that must be considered in operation. In which case, the regulation is considered at transcription and translation levels or the stability of messenger RNA. The aforementioned can only work in regulation based on the synthesis of a particular protein. Consequently, it comes out as a subject of importance to investigate the regulation of transcription of bacterial genes. For this case, Escherichia coli (E. coli) is used as the bacteria to induce synthesis of enzyme β-galactosidase.Escherichia coli (E. coli) can produce the enzyme β-galactosidase which breaks lactose into galactose and glucose. Synthesis of the enzyme beta-galactosidase is induced in wild-type E. coli strains in response to the presence of lactose, the enzymes natural substrate (Ring, 1999, 80). The inducer, lactose, is usually the molecule broken down by the enzyme system. Worth noting is the ability of E.coli to solely use lactose as a carbon source regardless of the presence of glucose. A more stable inducer that lactose, IPTG (Isopropyl β-D-1-thiogalactopyranoside) helps in inducing expression of the enzyme without being metabolized in the process.Apart from induction, synthesis of β-galactosidase is also influenced by catabolite repression. The process involves slow down of the synthesis process, facilitated by lactose, especially when a presence of glucose is detected. Intuitively, glucose acts as a better energy and carbon source than lactose (Wallenfels, 1972, 67). When given both sugars, E.coli will not synthesize beta-galactosidase until all of the glucose is first exhausted from the medium.