IGEM:VGEM/2007/Projects

Projects
The following projects represent a small fraction of the plethora of project ideas that we brainstormed during the spring semester and early summer. Many of our initial project ideas were either too expensive or depended on knowledge that does not exist yet. Therefore, only a small percentage of these were deemed plausible near the beginning of the summer, but most eventually met similar roadblocks. We will present our work on Harvesting Biomass and Light to Power Butanol Biosynthesis at the iGEM Jamboree in November. It is our wish that the 2008 VGEM Team will investigate the remaining designed projects in more detail.

Butanol Biosynthesis
Coming up with alternative fuels is a real-world problem. We're interested in using cheap, renewable feedstock to power efficient biofuel production. More to come!

Bacterial Melanogenesis
This project is an extension of work that was done at Biosource Genetics Corporation in 1990. What we would like to do is program bacteria to produce melanin in response to a red light stimulus. This inducible melanin production has various applications including making melanin for monitoring cellular processes. In this way, melanin would serve as a biomarker or indicator similar to the GFP but would be easily visible to the naked eye.

We have designed a light-inducible system in E. coli capable of manufacturing and secreting melanin. This biological machine is built from two standard biological parts, a melanin generator and a red light-inducible plasmid. This project has a very simple design: the melanin producing gene mel from Streptomyces is linked to the red-light inducer designed by UT Austin in the iGem 2006 competition.

Motivation

According to the American Cancer Society, skin cancer is the most common form of all cancers. It accounts for nearly half of all cancers in the United States. Due to its natural defense mechanism, skin must first be exposed to UV radiation before melanogenesis begins. Thus, we thought it would be convienient to be able to produce melanin in response to another harmless wavelength. This technology may, in the future, lead to treatments for albinism and a safe alternative for cosmetic tanning. Melanin may also be used as a natural indicator in the laboratory as well as an acoustic material. According to a study by Kono, et. al., melanin is capable of absorbing ultrasound.

Additionally, we would like to be able to use the melanin secretion system as an indicator in our ethylene detection project. Theoretically, more and more melanin would be secreted as various produce items become riper and produce more ethylene, causing the indicator to become darker on a gradient.

Background

In humans, melanin is found in the skin, hair, iris, adrenal gland, inner ear, and various pigment-producing regions of the brain.

Melanin is the primary determinant of skin color. The process of tanning originates in specialized cells called melanocytes. When stimulated by ultraviolet radiation, these cells produce melanin, which then migrates to the neighboring keratinocytes. The melanin accumulates above the receiving cells' nuclei in order to protect genetic material from from mutations caused by the sun's ionizing radiation.

Though there are many types of melanin, they are all polymers which contain derivatives of the amino acid tyrosine. Melanin is an aggregate of smaller component molecules; the various types of melanin have differing proportions and bonding patterns of the component molecules. Three types of melanin found in humans include eumelanin, pheomelanin, and neuromelanin. Eumelanin, which produces a brown-black color, is most common.

Ethylene Biosensor
NOTE: This project has been put on the back burner.

During one of our brainstorming sessions we were discussing possible biosensors and came up with a fairly practical project idea: an ethylene biosensor. Why sense ethylene? Mature fruit produce and release ethylene as they ripen. Measuring the concentration of gaseous ethylene on or near the surface of the ripening fruit would allow for the indirect measurement of its degree of ripeness.

Synthetic Biological Clock
NOTE: This project has been put on the back burner.

The synthetic biological clock was one of our earliest project ideas and involves the coupling of Elowitz and Leibler's repressilator system to some actuator such as fluorescence or aroma generation. We would like to link MIT's 2006 iGEM project to the repressilator and create an aroma therapy clock in addition to linking green, yellow and red fluorescent proteins to the repressilator to make a molecular traffic light. Future applications of controlled synthetic oscillatory systems include internal, autonomous drug delivery technology.

Cellular Photosignalling
NOTE: This project has been put on the back burner.

This system incorporates the idea of the repressilator on a larger scale, using three distinct cell types that are chemically isolated from each other (i.e., not sharing medium) and are each equipped with genes that enable bioluminescence and photosensing. Cell type 1 is bioluminescent at a particular wavelength (e.g., blue). Cell type 2 produces yellow bioluminescence unless it perceives blue light. Cell type 3 produces bioluminescence at yet another wavelength (e.g., green) unless it senses yellow light. Green light represses cell type 1 blue bioluminescence. Thus, engineered cell-cell communication with light is possible, creating a "wireless" repressilator system.

Directed Angiogenesis
NOTE: This project has been put on the back burner.

Angiogenesis is crucial in many biological and disease processes. Usually stufied in the context of uncontrolled tumor growth, it is also a necessary element of wound healing and tissue engineering. A major problem with the application of engineered tissues is a lack of perfusion of the essential nutrients to keep the tissue alive, healthy, and properly integrated with the surrounding natural tissue. We would like to develop a natural phototaxis system in engineered bacteria which can be exploited to induce angiogenesis at targeted areas within the body. These living machines are programmed so that once they have arrived, they produce and secrete their payload (e.g., VEGF) and can be compared to "cellular dumptrucks".