17.1B: Molecular Products from Microbes
- Describe how Taq polymerase, restriction enzymes and DNA ligase are used in molecular biology
The expansion and growing popularity of the field of molecular biology has resulted in a higher demand for tools used to study molecular biology. The field of molecular biology specifically deals with the molecular mechanisms of a cell and focuses on the regulation of cellular interactions. Topics of particular interest within the field include gene expression (transcription and translation) and protein synthesis. Studying these mechanisms in the laboratory has been made possible by the use of molecules derived from microbes. The following is a brief overview of some of the molecular products derived from microbes that allow for the performance of popular molecular biology techniques.
Taq Polymerase
Taq polymerase is an enzyme that was first isolated from the microbe Thermus aquaticus . T. aquaticus is a specific type of bacterial species, a DNA polymerase, that is thermostable — it can withstand extremely high temperatures. The isolation of this polymerase has resulted in the ability to perform polymerase chain reactions (PCR), a process used to amplify DNA segments, in a single step. Prior to the isolation of Taq polymerase, a new DNA polymerase had to be added to the reaction after every cycle because of thermal denaturation. With the addition of Taq polymerase to the reaction tube, the cycle can be performed much more quickly, and less enzyme needs to be used. Currently, Taq polymerase is manufactured and produced on a large scale and is available for commercial sale.
Restriction Enzymes
Restriction enzymes are a specific class of enzymes isolated from various bacteria and archaea, in which they grow naturally as a means of protection against viral infection. These enzymes have the ability to cut DNA at specific recognition sequences and have served as invaluable tools in DNA modification and manipulation. The enzymes have the ability to recognize foreign DNA and cut it up. The bacteria and archaea from which these enzymes are isolated from have innate mechanisms to protect their own DNA sequences from these enzymes, such as methylation. The isolation of approximately 3000 restriction enzymes has allowed molecular biologists to utilize them in processes such as cloning and the production of recombinant DNA.
DNA Ligase
Another enzyme that was isolated from T. aquaticus and that has been undeniably important to the field of molecular biology is DNA ligase. DNA ligase plays a key role in molecular biology processes due to its ability to insert DNA fragments into plasmids. The process of DNA ligation is defined as the ability of DNA ligase to covalently link, or ligate, fragments of DNA together. In molecular biology — specifically, during the process of developing recombinant DNA — DNA ligase can be used to ligate a fragment of DNA into a plasmid vector. The most commonly used DNA ligase is derived from the T4 bacteriophage and is referred to as T4 DNA ligase.
Key Points
- Various enzymes can be isolated from microorganisms and utilized in recombinant – DNA production.
- The ability of some archaea to thrive in extreme environments has led to analysis and isolation of important molecular components of the organisms, such as Taq polymerase, that have contributed to modern molecular biology techniques.
- Modern-day molecular biology techniques rely heavily on specific enzymes and molecular components derived from microbes, including DNA ligase and restriction enzymes.
- DNA ligase functions by covalently linking, or ligating, DNA fragments.
- Restriction enzymes function by recognizing and cutting specific sequences within DNA.
Key Terms
- polymerase chain reaction : A technique in molecular biology for creating multiple copies of DNA from a sample; used in genetic fingerprinting etc.
- restriction enzymes : an endonuclease that cuts DNA at specific recognition sequences