ECOLOGICAL BIOCHEMISTRY - Study Guide - V. M. Isaenko 2005

Chapter 11. ECOLOGICAL BIOCHEMISTRY AND BIOTECHNOLOGY

11.2. Biotechnology and Genetics

To optimize production processes involving living organisms, improving their genetically determined properties is paramount. Traditionally, mutagenesis followed by screening and Selection of desired variants is employed to increase the productivity of microbial strains. This exact approach successfully enhanced the yield of Antibiotics synthesized by actinomycetes and Fungi.

The simplest way to create organisms with targeted genetic traits is by crossing strains belonging to opposite mating types.

In Bacteria, Cell-to-cell contact during sexual reproduction (conjugation) occurs via The formation of a conjugation bridge, which facilitates DNA transfer from one cell to another. This capability is encoded in numerous Plasmids.

Fungi exhibit various Mating Systems. Most ascomycetes and Basidiomycetes possess mating systems that prevent self-Fertilization and Other forms of Inbreeding.

Many industrial filamentous fungi lack a true sexual cycle that would allow crossing to generate high-yielding strains. Instead, a range of Methods is used to achieve recombination in these organisms. Specifically, heterokaryons—containing genetically distinct nuclei within a single cell—can be obtained by the fusion (anastomosis) of hyphae from different mycelia or through the formation of a mutant Nucleus within the mycelium.

Many bacterial properties are encoded by plasmids—circular DNA molecules transmitted to bacterial progeny independently of the chromosomal DNA.

Transposons are widely used to obtain mutants and clone desired genes in bacteria. These are bacterial DNA segments capable of moving as a whole from one genomic site to another, carrying various genes (encoding resistance to antibiotics, toxins, additional metabolic Enzymes, etc.). Transposons can serve as markers for genes targeted for cloning.

Interspecific hybrids can be obtained via protoplast fusion—Cells stripped of their cell walls. This method is extensively applied to generate hybrids of bacteria, fungi, plants, and animal cells. Notably, the fusion of mammalian cells has yielded so-called hybridomas capable of producing Monoclonal Antibodies. These are utilized in Diagnostics, particularly for Tissue and organ typing prior to transplantation. Monoclonal antibodies are also employed for the purification of Proteins and Other Compounds via immunoadsorption.

Introduction/32.html">Genetic Engineering techniques are utilized to produce a variety of proteins. First, the Gene of interest is isolated. If an animal gene is to be expressed in bacterial or Yeast cells, the corresponding mRNA is typically isolated initially. Following its METABOLISM/31.html">Transcription into complementary DNA, the latter is integrated into plasmids or bacteriophage genomes acting as vectors. Subsequently, the recombinant plasmids containing the inserted complementary DNA molecules are introduced into suitable bacterial or yeast host cells.

A prime example is the Synthesis of the gene for the Insulin precursor, which was inserted into the DNA of Escherichia coli. After purification, proinsulin was cleaved with Trypsin and β-carboxypeptidase to yield insulin. Recombinant DNA technology has also enabled The production of Growth Hormone, various Vaccines, and other biologics.