Course: SAT 170 Introductory Biotechnology

Unit 9 Learning Module

SubTabs

- Unit 9
- Table of Contents (Selected)
- Unit 9 Key Terms (Selected)

Page 2 of 4
Roles of Microorganisms in Biotechnology

The process of wine fermentation involves yeast which metabolize the sugars in the fermentation chamber and produce alcohol and carbon dioxide (the source of the bubbles shown here) as a byproduct.

Microorganisms serve as the source for the majority of antibiotics that have been isolated and purified for therapeutic uses. Recall from unit 1 that in 1928, Alexander Fleming discovered penicillin from the fungal organism Penicillium notatum. This antibiotic represented the first really effective and widely used antibiotic; since that time many more antibiotics have been discovered and isolated from a variety of microorganisms.  In addition, some antibiotics that were originally isolated from microbes are being modified or used as templates for synthetic antibiotics. This modification of original antibiotics is a focus of many biotechnology companies as the development of these new drugs is becoming increasingly necessary due to the fact that microbes are becoming resistant to these drugs. We will explore the topic of antibiotic resistance in much more detail at the end of this unit.

One of the other roles that microbes play in biotechnology is for the production of certain foods. Recall from unit 1 that humans have been utilizing microorganisms for producing foods such as bread, wine and different types of cheese via a process known as fermentation. Fermentation is a metabolic process that is used by many microbes including bacteria and fungi.

Recall from unit 5 that bacterial and fungal organisms are often used for upstream processing of proteins. In this role, these organisms serve as factories for the synthesis of proteins which can have many applications especially in the medical and industrial fields as we will see in future units. Recall that when choosing a host cell for the synthesis of proteins several factors must be considered. Bacteria are often considered a good choice for upstream processing of proteins because they can be easily genetically modified and the culturing methods for bacteria are generally quick and simple. Fungi also exhibit these characteristics which makes them ideal protein factories. In addition, since they are eukaryotes they possess the organelles necessary for modifications of proteins post-translation.

You may also recall from our discussion of DNA technology in unit 6, that bacteria are the primary source for restriction enzymes, especially those enzymes that are commonly used in recombinant DNA research. Recall that a restriction enzyme is a type of endonuclease (enzyme which cuts nucleic acids) that cuts at a specific sequence of nucleotides known as a restriction site. The restriction enzymes that leave “sticky ends” as they make a zig-zag cut in the DNA molecule can be used to create recombinant DNA molecule since two sources of DNA that are cut with the same restriction enzyme will have complementary “sticky ends." See unit 6 for a more thorough review of this information if needed.

This restriction enzyme was isolated from the bacterium Escherichia coli, naming it EcoR1. When this enzyme cuts the DNA sample it creates the “sticky ends” necessary for creating recombinant DNA.

Another example of useful enzymes that have been isolated from microorganisms was also discussed in unit 6 in the description of the polymerase chain reaction (PCR). Recall that Taq polymerase, which is the specific type of DNA polymerase that is used in PCR, was originally isolated from the bacterial species Thermus aquaticus. This unique polymerase is able to withstand the temperature changes of the PCR because it was isolated from a thermophile bacterium, which thrives in extreme temperatures.

When describing DNA libraries, we introduced the concept of cloning vectors. We also discussed the role of such vectors in gene therapy and the production of genetically modified organisms (GMO’s). You may recall from unit 7 where we covered these topics that these vectors included things like plasmids, bacterial artificial chromosomes, yeast artificial chromosomes and viruses. Recall that a plasmid is a small, circular, double-stranded, extra-chromosomal piece of DNA commonly found in bacteria which can be used as a cloning vector for DNA libraries as well for the transfer of DNA into an organism for the generation of a genetically modified organism. Bacterial Artificial Chromosome (BAC) and Yeast Artificial Chromosome (YAC) are cloning vectors often used in the construction of DNA libraries and are expressed in bacteria and yeast, respectively. You may also recall that a certain type of virus known as a retrovirus was used in the construction of a specific type of DNA library known as a complementary DNA (cDNA) library. cDNA libraries are valuable tools for biotechnology because they consist of cDNA molecules that correspond to the complete set of genes of a particular organism. Recall that a cDNA molecule is one which has been reverse transcribed from an mRNA molecule using the enzyme reverse transcriptase (RT).  This enzyme is capable of synthesizing a cDNA molecule from an mRNA template and was originally isolated from a retrovirus. Also recall from unit 7, that such retroviruses can also be used for the delivery of genetic information during the process of gene therapy.

Although many different organisms can be used for the purpose of bioremediation, most organisms involved in bioremediation are microorganisms. Such microorganisms are known as bioremediators. The role of these bioremediators is to remove pollutants from the environment. This is possible because of the unique metabolism of these organisms. In some cases, these metabolic properties are innate to a particular species, while other organisms are capable of bioremediation only after having been genetically altered to carry the genes for specific enzymes needed for a particular type of bioremediation. You may recall from unit 1 for example, that Anada Chkrabarty genetically modified a microorganism to consume oil for the purpose of cleaning up oil spills. In cases where the pollutant is removed by these bioremediators at the site of contamination, it is classified as in situ bioremediation. In some cases the microorganisms are already present and may only require additional nutrients or environmental conditions to stimulate their growth. If the contaminated material is removed from the original site to be treated elsewhere, it is referred to as ex situ bioremediation. Other forms of bioremediation are known as mycoremediation and phytoremediation because they rely on the action of fungi and plants, respectively, for the removal of pollutants from the environment.

During the clean-up of the Valdez oil spill in Prince William Sound, Alaska in 1989, workers relied on microorganisms which were able to degrade the oil contaminants.

Mine tailings can be found all over the world and often times contain harmful contaminants like asbestos.
Thousands of abandoned mines throughout the world are having significant impacts on our environment including contamination of water and soil with mining related arsenic and other toxic compounds. Often associated with an abandoned mine is a mine tailing which represents the left over materials of the ores which are present after the traditional methods of removal of the valuable minerals have been used.

Biomining, or bioleaching, is a process that utilizes organisms, most often microorganisms, to remove valuable minerals for the ores in which they are trapped without generating such tailings. In fact, many microorganisms can be used to further extract valuable minerals from these tailings and some may even be used to remove some of the toxic materials present in these tailings. This is one of the major advantages to using microorganisms for mining out these materials since you can avoid the use of extreme heat or toxic chemicals that are often used in traditional mining methods. In addition to being less impactful on the environment, biomining is often more effective and less expensive than traditional mining methods. Biomining can be used to release a variety of valuable minerals including things like copper, cobalt, nickel, silver and gold. A variety of different organisms with different metabolic capabilities are used for biomining. Such organisms are said to be lithotrophs because of their ability to use inorganic substrates, usually minerals, as part of their metabolism. In addition to being lithtrophs, microorganisms used for biomining are often thermophiles (because they thrive at elevated temperatures), and/or acidophiles (because they thrive in environments with relatively high amounts of acids); both of these conditions are commonly found in the biomining process.
Shown here are large clusters of ore which contain important minerals.