Quiz 5: Microbial Biotechnology


A number of structural differences are present between prokaryotic and eukaryotic cells. Some important differences are: i) Prokaryotes (bacteria and archae) do not have a nucleus and their genome consists of a single circular DNA (deoxyribonucleic acid) molecule. Eukaryotic cells (fungi, animal cells, plant cells, and protozoa) have a well-defined double membrane-bound nucleus that contains the chromosomes, which consist of DNA molecules compacted by histone proteins. Prokaryotic DNA lacks histones. ii) Prokaryotes do not have membrane bound organelles, whereas eukaryotes have various types of membrane-bound organelles with different functions such as endoplasmic reticulum, Golgi apparatus, lysosome, nucleus, and mitochondria. iii) Prokaryotes have cell walls that are structurally different from cell walls of eukaryotic plant cells. Bacterial cell walls contain peptidoglycan, which is a complex protein and polysaccharide structure. Role of prokaryotes in biotechnology: Due to their small genome size, rapid growth rate, and easy manipulation of genomes, prokaryotes have been extensively utilized in various biotechnology applications. Bacteria have been used for: • Production of recombinant proteins for therapeutic uses such as insulin for regulation of body uptake of glucose in diabetic patients; • As a source of antibiotic drugs such as penicillin, bacitracin, and erythromycin and production of vaccines such as DPT (diphtheria, pertussis (whooping cough) and tetanus) vaccine. • As hosts of gene cloning procedures; • In production of various types food and beverages such as bread, yogurt, beer, and other alcoholic beverages.

Difference between yeasts and bacteria: Bacteria are prokaryotic cells, characterized by the absence of membrane-bound cell organelles, nucleus, and the presence of a single circular DNA as chromosome. In contrast to bacteria, yeasts are eukaryotic unicellular fungi; therefore, they have structural characteristics of eukaryotes such as well-defined nucleus and cell organelles, and larger genome consisting of more than one chromosome. Applications of yeasts in biotechnology: i) The ability of yeasts to ferment sugars is applied for the production of many food products such as bread, beer, and wine. ii) As yeasts are simple eukaryotes and have several genes common with human genome, yeasts such as Saccharomyces cerevisiae have been used as model eukaryotic cells in study of areas such as eukaryotic gene functions, cell cycle, metabolism, and diseases. iii) Yeasts have been used in several biotechnology techniques such as the yeast-two hybrid system that is used to study protein interactions and functions.

Calcium chloride transformation: Transformation is the ability to take DNA from surrounding environment by bacteria, mediated by recombinant DNA cloning. The steps of calcium chloride transformation involved in binding of DNA (deoxyribonucleic acid) to cells are, as follows: 1. In vitro conditions, bacterial cells are induced by intake of foreign DNA, facilitated by calcium chloride treatment. 2. The E.coli is transformed with jellyfish gene containing plasmid, for green fluorescent protein. 3. The bacterial cells that are transformed glow bright green. 4. This indicates the uptake of plasmids with green fluorescent proteins gene. 5. Thus, plasmids with GFP gene express GFP mRNA and protein. The following diagram depicts the transformation of bacterial cells: img The following steps are involved to enter DNA into the cells. 1. Plasmid is introduced in bacterial cells by transformation. 2. Bacterial cells replicate recombinant plasmids. 3. The treatment involves is ice-cold calcium chloride. 4. Cations in calcium chloride break the membrane. 5. Therefore, the cells of the bacteria form pores. 6. Pores enhance the entrance of DNA. Electroporation: Electroporation is a common technique for transforming cells through electric shock. Advantages of electroporation over calcium chloride procedure in transformation: 1. The cells are exposed to electric field to generate holes in the cell membrane. 2. The new DNA is then transferred through holes. 3. A gene gun can also be used, for the transfer of desired genes into the plant genome. The instrument transfers gold or tungsten particles coated with the desired DNA fragments into the cells. 4. Once the desired gene is transferred into the genome, recombinant cells can be grown in presence of nutrients and hormones. 5. Thus, the adults produce desired characteristics. 6. Some examples of genetically engineered plant are golden rice, Bt cotton etc.