Techniques for the Investigation of Lac Operons

The microorganism used in this laboratory is E. coli which is a prokaryote. Typically, prokaryotes are small, compact genomes with a single circular DNA molecule. The genes are dense and there is little space between them. In the case of E. coli, it has thrA, 1 nucleotide, thrB, thrC. Enzymes of a single biochemical pathway are encoded by the operon: since no introns are present, all genes are not interrupted and the sequences are nonrepetitive. An operon is a group of contiguous genes transcribed into a single polycistronic mRNA molecule as a single unit.

 - Galactosidase is an enzyme involved in cleavage of lactose into glucose and galactose, encoded by the lac Z gene of the lac operon. (Glick et al., 2010) prevented the lac operon transcription by inhibiting the lac promoter. Activation of the promoter can be achieved by adding lactose or isopropyl-β-D-thiogalactopyranoside (IPTG) to the medium. Lactose and IPTG only block the binding of the lac repressor (the product of the Lac I gene) to the promoter. (Glick et al 2010)

In bacteria, bacterial Escherichia coli has an effective mechanism for metabolizing lactose. All three proteins important for lactose metabolism are encoded by expressible DNA units called the lac operon. The lac operon consists of three structural genes, a promoter, a terminator, a regulator and an operon. The structural gene in the lac operon encodes three proteins involved in the metabolism of lactose in E. coli. They are involved in the transport of β-galactosidase; β-galactoside permease, which is involved in the conversion of lactose to glucose and galactose; transporting lactose intracellularly; and finally β-galactoside transacetylase, its function is It is unknown.

An auxotrophic mutant requires specific nutrients or compounds to grow and express its phenotype (Madoka). Bacterial growth involves the lac operon. It is therefore important to understand the function of the lac operon. The lac operon has three genes that require lactose metabolism: lacZ, lacY and lacA. lacZ encodes β-galactosidase, lacY encodes β-galactosidase permease, and lacA encodes lactose transacetylase. . (2) (1) In this experiment, we describe several methods for detecting the lac phenotype. One way is to use a minimum lactose medium. In this medium, Lac- does not proliferate and Lac + proliferates. The second way is to use MacConkey media. MacConkey's medium is a pH-sensitive medium that exhibits red color in acidic media. In this medium, both Lac + and Lac - grow on the plate, but only Lac + turns red. The reason is that Lac + fermented lactose produces an acid metabolite, which lowers the pH of the medium.