Team:Enloe Raleigh

From 2014hs.igem.org

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Project

As technology progresses, humans have begun to explore new methods of pollution reduction. Coal production is the single largest power source in the US and contributes heavily to industrial pollution. Although coal will eventually be replaced with more efficient and less polluting energy resources, at this point in time, there exists no combination of renewable energy sources that could replace the global dependency on fossil fuels, particularly coal. Here arises a need to control pollution caused from burning these fossil fuels. This includes fixing notorious emissions of sulfur dioxide, nitrous oxides, and carbon dioxide when solid coal or gaseous coal is burned and the semi-solid wastes composed of toxic metals such as lead and mercury. The most worrisome of these are carbon dioxide, nitrous oxides, and sulfur oxides, which are widely acknowledged to be the primary cause of global warming, and photochemical smog with approximately 15 tons added to the atmosphere annually. Although there are synthetic ways to reduce the detrimental effects of burning coal, such as coal gasification, chemical looping, and the use of an SNOX reduction system, such methods either require high maintenance, or are not cost-benefit effective. To overcomes these problems, we have devised a natural, biochemical system using versatile microbes to reduce sulfur oxide emissions through the Sulfate Reducing Bacteria (SRB), Desulfovibrio orientis. Furthermore, ways to test for air quality levels are not dynamic (in real-time) and do not do so in a cost effective method. As a result, we plan to add fluorescent capabilities to our bacteria that vary in intensity corresponding to different gradations (in ppm) of specific pollutant, in this case the sulfur oxides. As a result, we provide a new, synthetic biological alternative to measure air quality whilst reducing pollution at the same time.

Unlike other species of the Desulfovibrio genus, D. orientis is one of only a handful of species that has been shown to reduce sulfur dioxide, not sulfate, into hydrogen sulfide. In this reaction, SO2 acts as an electron acceptor and is reduced to H2S during cellular respiration. In addition, given D. orientis’ similar metabolism and anaerobic behavior as many hyperthermophiles of the domain Archaea, the species is more inclined to be thermophilic (or favorably hyperthermophilic - having the ability to thrive in extremely high temperatures). Furthermore, this species has been observed to live off minimal mineral nutrients, heat- and alkali-pretreated municipal sludge, CO2, SO2, and H2, and thus requires little nutrients to survive above a critical threshold. Since the species already contains the catalytic gene sequence to carry out the aforementioned favorable sulfate reducing metabolic activities, we plan to genetically spice protein coding sequences for fluorescent proteins, such as that from the jelly fish, Aequorea victoria. This gene would be linked to the genes associated with the sulfate reducing catalytic activity of D. orientis so that the bacterial species would only glow when the metabolic processes to reduce sulfur oxide derivatives are active. An extension, would be to express the fluorescent protein genes in a fashion that correspond to the different levels of sulfur dioxide (in ppm) present in the environment by either varying color or intensity. A possible method is the inclusion of a highly sensitive modified RNA thermometer (several base units upstream from the fluorescent protein gene) that regulates the activation of the genes that codes for the production of the desired fluorescent proteins based on the free energy (delta G) of the system. The previously mentioned reaction of D. orientis tends to add to the free energy of the system, and thus its metabolic activity can be measured by the differential change of free energy in the system. The RNA thermometer would then increase translation of the fluorescent proteins as the free energy increases.

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Fun!

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