So what’s the point of iGEM?
The competition has a wide range of goals and plays a massive role in the field of synthetic biology. Its primary aim is to provide students with the materials to create their own projects using genes from the iGEM repository. and to ultimately inspire the next generation of young scientists. Teams can utilise these genes by expressing them in living cells of their own choice (usually bacteria) to generate novel characteristics or ‘phenotypes’ in the host organism that can be used for a purpose. Furthermore, they can extract or synthesize other genes that they may wish to use in their project and submit these genes to iGEM HQ to add to the repository. This means that the iGEM database of genes and other functional DNA parts or ‘biobricks’ is constantly built upon every year and gets bigger. By using these ‘biobricks’ teams can create complex genetic circuits in organisms to meet the aims of their project. The projects are incredibly diverse ranging from the genetic engineering of colour changing bacteria (Cambridge iGEM 20091 to generation of tumour killing bacteria (Tronheim iGEM 2012)2 These projects can be used to tackle real life problems and can provide promising new applications for the future. An example of this is Edinburgh’s ‘Arsenic Biodetector’ in 20063. The team developed a system whereby bacteria could detect arsenic in water systems and emit a pH signal in response. The concept behind this project has major implications for regions where arsenic contamination of drinking water poses a serious problem such as Bangladesh and Nepal, with a need of a safe, non-toxic, and sustainable method of arsenic detection. There is currently a large initiative, ‘The Arsenic Biosensor Collaboration’, that is utilising this technology to develop a commercially viable biosensor for use in South East Asia.
Team projects are assessed on a wide range of criteria with awards given in tracks such as: best environment project, best energy project, best new application project, and best art project, just to name a few. One of the criteria to achieve a medal is that there is an element of human practices. Teams are required to spread the word of their project to the general public as well as collaborate with other iGEM teams. Thus, iGEM also aims to make the field of synthetic biology better known and has an educational component.
So this year, a team of eight undergraduates at the University of Kent (including myself) have been spending the summer working on their project to submit to iGEM. The aim of the project is to genetically engineer a strain of E.coli to produce aroma compounds for use in the fragrance and flavourings industry. In particular, we investigated the generation of a class of odorants known as terpenes. Terpenes are a diverse class of organic compounds, produced by a variety of plants, particularly conifers, and they are typically the primary components of many plant essential oils. Of these terpenes, we intended to produce limonene (a lemon smell), zingiberene (a ginger smell), and R-linalool (a lavender scent). Terpenes are typically produced in plants via a biochemical pathway known as the mevalonate pathway (see figure 1). Intermediates of this pathway are converted into specific terpenes by terpene synthase enzymes. Unfortunately, the mevalonate pathway does not exist in bacteria; therefore, to optimize odorant production, we expressed this pathway in E.coli by transforming bacteria (ie. getting bacteria to uptake DNA) with the plasmid pBbA5c-MevT-MBIS5 , which contained genes encoding components of the mevalonate pathway.
(Related: for in-depth reviews of modern terpenes: https://www.true-blue.co/ )
The terpene synthase genes we selected as our novel biobricks were genes encoding Zingiberene synthase (converts farnesyl-PP into zingiberene to produce a ginger odour) and R-linalool synthase (converts gernyl-PP into R-linalool to produce a lavender scent), taken from the grass Sorghum bicolour and lavender respectively. We searched for these gene sequences on an online database (uniprot6) and then manipulated the sequences for optimal expression in E.coli on a computer before ordering them to be synthesised as gene fragments by the DNA synthesis company Life Technologies. We took these gene fragments and put them in plasmids for expression in the bacteria.We also used limonene synthase (provided in the iGEM kitplates) in our project, which converts gernyl-PP into limonene to produce a lemon smell.
Implications of the Project:
The generation of odorant molecules using bacteria could present an interesting scientific development for the future. The cosmetic and perfume industry is huge, with industry analysts estimating its worth to exceed $33 billion by 20158. Fragrances are typically produced by chemical synthesis, in which dangerous chemicals are often used, or by natural distillation and extraction of plant oils. These processes are relatively inefficient and costly so a lot of research into the use of using microbes to produce perfumes is being carried out. In fact, in March 2012, BASF announced that its venture arm has invested $13.5 million in the San Diego-based biotech firm Allylix for this purpose. The use of bacterial perfume production also is less susceptible to variable environmental factors affecting yield. Plant crop yields are dependent on many factors and can be greatly affected by natural disasters, meaning that often the supply fails to meet the demand. For example, a shortage in Patchouli oil from Indonesia has resulted in an incredible price rise in recent years. The use of bacteria may, therefore, provide a more reliable source of aroma compounds since it’s lab environment can be more carefully controlled. Furthermore, if this method were to become commercially viable, it could free up land used for plant crops for other uses. In a world where food shortage is becoming an increasing problem, freeing up more land for food crops can have massive implications.