Genetics - A. V. Syvolob 2008

Genetic Engineering and Methods of Molecular Genetics
Genetic Engineering of Microbiological Systems

Genetically modified microorganisms are primarily used as bioreactors that produce Proteins for medical purposes.

These are mainly small proteins that do not undergo post-translational modifications. One of the earliest Industrial Applications of Introduction/32.html">Genetic Engineering was The production of the human Growth Hormone, somatotropin, via expression in E. coli Cells (following the schematic diagram in Fig. 9.9). In the body, it is secreted by the anterior Pituitary Gland, and its deficiency causes Pituitary dwarfism.

The production of Somatostatin is an interesting example of targeted protein design using Genetic engineering Methods. It is a short peptide (containing 14 amino acid residues) synthesized in the gastrointestinal tract, which inhibits the release of growth hormone from the pituitary gland. Obtaining somatostatin in bacterial cells in significant quantities is challenging because it is rapidly degraded by Proteolytic Enzymes. To "bypass" intracellular bacterial proteases, a chimeric precursor protein was constructed. It incorporated a bacterial protein as its N-terminal region, to which somatostatin was attached—of course, all of this was done at the DNA level, with the triplet ATG encoding Methionine serving as the linking element in this construct. After isolation from the bacterial cells, the chimeric protein was treated with cyanogen bromide, resulting in its Cleavage at the methionine residue, thereby releasing the physiologically active polypeptide. A similar scheme was used to develop the production process for Insulin.

Interferons of all three groups—a-, ß-, and у-interferons, which are antiviral proteins synthesized by immunocompetent cells—are also produced via expression in E. coli. However, a drawback of using bacterial cells for the production of ß- and у-interferons (natural interferons of these two groups are Glycoproteins) is the lack of systems in Bacteria that ensure post-translational modifications of proteins. The Role of glycosylation of ß- and у-interferons is not fully understood, and although the non-glycosylated forms of these proteins retain virtually complete antiviral activity, this prompts the development and use of recombinant interferon expression systems in Eukaryotic cells.

An important place in the GENETIC ENGINEERING OF microorganisms is occupied by the production of recombinant Vaccines. They offer A number of advantages over traditional vaccines: they are characterized by the absence (or a significant reduction) of ballast components, almost complete harmlessness, and low cost. Three main approaches are used to obtain such vaccines:

✵ Modification of the microorganism through the deletion of genes responsible for virulence. At the same time, The ability to trigger an Immune Response is retained, and the microorganism can be used as a live vaccine.

✵ Transfer of antigenic determinants from a pathogenic microorganism to a non-pathogenic one, which can then be used as a vaccine.

✵ Cloning and expression of genes encoding proteins that contain antigenic determinants. These proteins are used as a vaccine that provokes an immune response.

The USE OF MICROORGANISMS for the industrial Production of organic compounds is of great significance. In such production, alongside classical technologies, Recombinant DNA technology is increasingly utilized, allowing for the targeted alteration of microbial METABOLISM by introducing new genes or modifying existing ones. Examples include The Use of recombinant microorganisms for the industrial synthesis of L-ascorbic acid (Vitamin C), the dye indigo, Antibiotics, valuable Biopolymers, and more.

Microorganisms can be beneficial not only through a specific product they synthesize, but also through their impact on the environment. In particular, bacteria can be used for the degradation of xenobiotics (unnatural synthetic chemicals such as herbicides, pesticides, refrigerants, and chemical waste). The main group of soil microorganisms that degrade xenobiotics consists of bacteria of the genus Pseudomonas. Different strains of Pseudomonas are capable of breaking down over 100 Organic compounds, but each individual strain uses only a specific group of related compounds as a carbon source and does not utilize others. By transferring Plasmids encoding enzymes of various Catabolic pathways into a single recipient strain, a "superbug" with extraordinary catabolic properties was created—it is capable of degrading most petroleum Hydrocarbons. Today, genetically modified strains of natural soil microorganisms are used for comprehensive biological wastewater Treatment.