Description
The Problem
![Mobirise](https://static.igem.org/mediawiki/2018/4/42/T--Stony_Brook--description_1.jpeg)
Figure 1. Greenhouse gases in the atmosphere [13]
Introducing Climate Change and Ocean Acidification
The increasing levels of carbon dioxide have numerous detrimental effects on the environment. Firstly, by trapping heat causes increases in global temperatures. These temperatures then power more intense weather events and melt ice reserves. Secondly, the ocean absorbs some of the excess carbon dioxide, leading to increasing acidity. Specifically, humans have caused oceans to become 30% more acidic since the Industrial Revolution [17], damaging coral reefs and other marine habitats in the process.
Cyanobacteria are one of the only organisms that have a historical precedent for changing the entire world’s climate and atmospheric composition. When trying to solve our carbon dioxide problems today, it makes sense to look back on nature’s example. Therefore, for our project, we chose to genetically engineer a well-studied and moderately fast-growing strain of cyanobacteria, Synechococcus elongatus PCC 7942 (S. elongatus), for the purpose of carbon capture. Specifically, we will engineer our cyanobacteria to efficiently produce and secrete a sugar called sucrose, which can be used in industrial fermentation to produce certain plastics and ethanol biofuel. By using cyanobacteria-derived sucrose as opposed to corn-derived sucrose, food prices for developing nations are not driven up, and unsustainable amounts of fertilizers and fossil fuels are not required [1]. By using cyanobacteria-derived sucrose over sugarcane-derived sucrose, deforestation and disruption of the natural ecosystems in the Amazon rainforest are reduced [2].
Photosynthetic cyanobacteria strains such as S. elongatus can produce sucrose more efficiently than both corn and sugarcane. Previously engineered S. elongatus has consumed carbon dioxide and secreted roughly 80% of that carbon intake as sucrose [3]. Crops such as sugarcane only allocate 15% of their carbon as sucrose, and large amounts of land and fertilizer are required for their production [3]. Because of the high efficiencies involved, sucrose production from cyanobacteria may be an effective method for carbon capture by converting carbon dioxide into sugars that can be used to make stable, high-value products such as bioplastics and biofuels.
![Mobirise](https://static.igem.org/mediawiki/2018/c/cd/T--Stony_Brook--description_4.png)
Figure 2. Photosynthesis consumes carbon dioxide. In our system, photosynthesis is designed to produce sucrose, a useful industrial product.
Our Project
Sucrose BioBricks
![Mobirise](https://static.igem.org/mediawiki/2018/c/c6/T--Stony_Brook--description_2.png)
Figure 3. CscB (sucrose symporter) pumps sucrose across the cell membrane using a proton gradient.
Promoter Biobricks
![Mobirise](https://static.igem.org/mediawiki/2018/b/b1/T--Stony_Brook--description_3.png)
Figure 4. Our regulatory promoters
Application of Novel Promoters
Lab Automation, Directed Evolution, and Open-Source Protocols
This year, our team had the honor of winning an Opentrons OT-2 robot that we used for lab automation. We programmed several protocols with the Opentrons, including InterLab protocols and well plate setups.
- Pimentel, D. (2003). Ethanol Fuels: Energy Balance, Economics, and Environmental Impacts Are Negative. Natural Resources Research
- Jusys, T. (2017). A confirmation of the indirect impact of sugarcane on deforestation in the Amazon. Journal of Land Use Science
- Ducat DC, Avelar-Rivas JA, Way JC, Silver PA (2012). Rerouting carbon flux to enhance photosynthetic productivity. Appl Environ Microbiol.
- Qiao, C., Duan, Y., Zhang, M., Hagemann, M., Luo, Q. and Lu, X. (2017). Effects of lowered and enhanced glycogen pools on salt-induced sucrose production in a sucrose-secreting strain of Synechococcus elongatus PCC 7942. Appl Environ Microbiol.
- Klahn S, Hagemann M. (2011). Compatible solute biosynthesis in cyanobacteria. Environ. Microbiol.
- B.W. Abramson, B. Kachel, D.M. Kramer, D.C. Ducat. (2016). Increased photochemical efficiency in cyanobacteria via an engineered sucrose sink. Plant Cell Physiol.
- Michel KP, Pistorius EK, Golden SS. (2001). Unusual regulatory elements for iron deficiency induction of the idiA gene of Synechococcus elongatus PCC 7942. J Bacteriol
- Kunert A., Vinnemeier J., Erdmann N., Hagemann M. (2003). Repression by Fur is not the main mechanism controlling the iron-inducible isiAB operon in the cyanobacterium Synechocystis sp. PCC 6803. FEMS Microbiol.
- Tsinoremus, N, Schaefer, M, and Golden, S. (1994). Blue and red light reversibly control psbA expression in the cyanobacterium Synechococcus sp. strain PCC 7942. J. Biol. Chem.
- Zhou J, Zhang H, Meng H, Zhu Y, Bao G, Zhang Y, Li Y, Ma Y. (2014). Discovery of a super-strong promoter enables efficient production of heterologous proteins in cyanobacteria. Sci Rep
- Keith DW, Holmes G, St. Angelo D, Heidel K. (2018). A Process for Capturing CO2 from the Atmosphere. Joule
- Welch C. (2017). “Carbon Emissions Had Leveled Off. Now They're Rising Again.” National Geographic. https://news.nationalgeographic.com/2017/11/climate-change-carbon-emissions-rising-environment/
- What are the greenhouse gas changes since the Industrial Revolution?” American Chemical Society. https://www.acs.org/content/acs/en/climatescience/greenhousegases/industrialrevolution.html
- CO2 Levels. NASA, NASA, data.giss.nasa.gov/modelforce/ghgases/Fig1A.ext.txt.
- Susan Solomon, Gian-Kasper Plattner, Reto Knutti, Pierre Friedlingstein Irreversible climate change due to carbon dioxide emissions (Feb 2009) Proceedings of the National Academy of Sciences, 106 (6) 1704-1709; DOI:10.1073/pnas.0812721106
- Marshall M. (2015). “The Event that Transformed the Earth.” BBC Earth. http://www.bbc.com/earth/story/20150701-the-origin-of-the-air-we-breathe
- “What is Ocean Acidification?” PMEL Carbon Program. https://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F