Genetically Modified Organisms

Brief Description:

 

Genetically modified organisms are defined as “any living organism that possesses a novel combination of genetic material obtained through the use of modern biotechnology” (Llaguno, C.) In Llaguno’s Gentically Modified Organisms article, he further describes GMOs as organisms that have been derived from the use of recombinant DNA technology. By introducing a “genetic package”, which consists of the desired gene, promoter and marker gene to the parental organism, organisms can be modified to best fit their environments. The desired gene produces the necessary proteins, the promoter regulates the production of these proteins, and the marker gene allows for confirmation of successful transformations. Organisms that are formed in this way are known as transgenic organisms. The other subset of GMOs are genetically engineered organisms which originate from the use of genetic engineering technology. This is where DNA molecules are combined from multiple sources to form a new sequence of DNA, which are then transferred to an organism, yielding novel genes. There are two types of genetic modifications that can occur using recombinant DNA technologies. In the most commonly thought of class, alien or foreign DNA has been introduced that confers a novel phenotype and creates a transgenic organism. In the second type DNA tools were used to rearrange the existing DNA of an organism, termed “self-cloning”. The resulting organism may have a novel property but no foreign DNA was used to create that property.

In the case of agriculture, plants can be modified to exhibit resistance to certain pesticides or plant viruses by producing the required protein from the implanted gene. An example of a highly used GMO in agriculture is Bt corn. This is a variety of corn that has the gene from Bacillus thuringiensis to produce a pesticide that fends off the European corn borer. While this is a very beneficial attribute, there is concern that insects that feed of corn can eventually attain this pesticide resistance. Similarly as important is the concern that allergic reactions may occur in humans. For this reason BT corn has not been approved for human consumption, but has been allowed for cattle consumption (Magnus, D.)

Many countries regulate the use of GMO organisms. In some cases a GMO is defined by the technology used (recombinant DNA techniques) and in other countries the use of GMO is restricted to transgenic organisms with self-cloned organisms being exempt from regulations.

 

Application in Wine Microbiology:

Genetically modified yeast strains have been used to benefit the winemaking process in many ways, such as enhancing fermentation, raising yeast ethanol tolerance, improving sugar utilization and nitrogen assimilation, as well as altering sensory aspects of a wine. An example of a strain that was produced to enhance wine fermentation is the strain ML01. ML01 can concurrently undergo alcoholic and malolactic fermentation in the absence of lactic acid bacteria. This is possible because it has a malate permease gene from Schizosaccharomyces pombe and a malolactic gene from Oenococcus oeni. This is a beneficial trait to a S. cerevisiae strain because it allows microbial stability in a wine while decreasing the acidity, and also greatly decreases the time needed for the overall fermentation process. While ML01 can convert malate to lactic acid, it does not produce the same desired flavor attributes as a lactic acid bacteria.

Another example of a genetically modified yeast strain is MET10-932 which was made to decrease the evolution of H2S in wine production. Since hydrogen sulfides have negative impact on wine flavor and aroma, winemakers are interested in using yeast strains which are non-producers of this compound. MET10-932 is a beneficial strain because it prevents sulfide release due to a change in amino acid change 662 from threonine to lysine. From this strain any commercial yeast strain can be crossed by allele swap to gain this attribute, and currently UCD522 and several other yeast strains have already undergone this cross. If a genetic modification is transferred via normal genetic crossing and breeding it is not considered to be a GMO because recombinant DNA technology has been used. If recombinant DNA technology were used to transfer the MET10-932gene to a new strain, even if that strain was identical to the genetically breed equivalent, it would still be considered a GMO in some countries because recombinant DNA technologies were used to create the strain.

Modifications to yeast strains do not change essential characteristics to the parent strain in the fermentation process, but slightly alter their metabolic processes. However there are alterations that can have a sensorial effect on the wine, such as enhancing the glycerol production in a yeast, or deleting the ALD-6 gene. By enhancing glycerol production in yeast, ethanol production decreases by 1% and by removing the ALD-6 gene, acetic acid production is repressed – both of which change the sensorial aspect of a wine produced from the genetically modified organism compared to the host strain (Schuller, D.).

References:

  • Bisson, L. 2010, Winter. VEN 128 Lecture 11,University of CaliforniaDavis.
  • Llaguno, C. 2001, January - June. Genetically Modified Organisms, Science Diliman. 13: 1, 73-76.
  • Magnus, D. 2001, Spring. Genetically Modified Organisms, Medical Ethics. 1-6.
  • Main, G., Threlfall, R., Morris, J. 2007. Reduction of Malic Acid in Wine Using Natural and Genetically Enhanced Microorganisms. American Journal of Enology and Viticulture. 58: 3, 341-346.
  • Schuller, D., Casal, M. The use of genetically modified Saccharomyces Cerevisiae strains in the wine industry.http://repositorium.sdum.uminho.pt/bitstream/1822/1302/1/2005-GMY.pdf