Team:Cornell/project/background/lead

From 2014.igem.org

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The transport system being utilized for this project is a combination of the <i>merT</i> and <i>merP</i> genes from the transposon TN501 of <i>Pseudomonas aeruginosa</i>.  The genes  <i>merT</i> and <i>merP</i> are part of the <i>mer</i> operon which helps <i>P. aeruginosa</i> resist mercury toxicity.<sup>[14]</sup>  These two membrane proteins work together to transport Hg<sup>2+</sup> ions into the cell.<sup>[1]</sup>  Systems for sequestration of mercury have been successfully developed utilizing <i>merT</i> and <i>merP</i>.<sup>[15,16,17]</sup>  We hope to improve upon these systems by combining the <i>merT</i> and <i>merP</i> genes with a different regulatory system and by making all these genetic parts modular.  
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The transport protein being utilized for our project is the calmodulin-binding protein <i>CBP4</i> from <i>Nicotiana tabacum</i>.  This protein is structurally similar to non-selective membrane channel proteins from other eukaryotes and has been shown to confer nickel tolerance and lead hypersensitivity.<sup>[1]</sup> Transgenic plants overexpressing <i>NtCBP4</i> were found to have increased uptake of Pb<sup>2+</sup> ions into cells, likely leading to the increased toxicity.<sup>[1]</sup>  While it has been suggested that <i>NtCBP4</i> could possibly be used for bioremediation purposes and other attempts have been made at lead removal from water using genetically engineered organisms, to the best of our knowledge no attempt has been made at utilizing <i>NtCBP4</i> for precisely this purpose.<sup>[1],[2],[3]</sup>. We believe that the specificity of this transport protein for lead and its readily available sequence make it an ideal candidate for bioremediation.
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Revision as of 04:12, 16 October 2014

Cornell iGEM

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Project Background

Health Risks

Mercury is usually released into the environment by manufactories as emissions or waste. Eventually this mercury is discharged into the water bodies and then is converted by bacteria living in the sediment into methyl mercury. Methyl mercury can be ingested by smaller aquatic plants and animals. The danger here is that, through biomagnification, animals higher in the food chain will have larger concentrations of methyl mercury in their systems. This is dangerous especially for large fish, birds, and humans. Additionally, through bioaccumulation, small amounts of consumed toxins can build up within one’s system over time, leading to mercury poisoning. The most common form of mercury poisoning comes from methyl mercury. According to the Environmental Protection Agency, almost everyone in the world has trace amounts of methyl mercury in their bodies because of its abundance in our environment, but in larger concentrations, it can be dangerous.
Side Effects of Mercury Poisoning:

For infants and children:
  • Impaired neurological development
  • Impaired cognitive thinking, memory, attention, and language skills
  • Impaired fine motor and spatial visual skills

For adults:
  • "pins and needles” in the hands, feet, and around the mouth
  • impairment of the peripheral vision
  • lack of coordination of movements
  • impairment of speech and hearing
  • muscle weakness

Extreme cases of high mercury poisoning:[3]
  • Kidney and respiratory failure
  • Death

Case Study

Onondaga Lake: Commonly known as the “Most Polluted Lake in America”, Onondaga Lake suffers from industrial waste and sewage pollution (i.e. ammonia and phosphorus which cause high algal blooms and suffocation of other organisms in the Lake).

Since the 1800s Allied Chemical, recently succeed by Honeywell International, is credited for dumping a total of 165,000 lbs of mercury into the lake, resulting in the contamination of about 7 million cubic yards of lake-bottom sediments.[4] Their continuous polluting only ceased in the last few decades and has fomented tragic damage to the environment.[4]

Mercury contamination usually is caused by industrial emissions. The mercury enters the environment as an industrial emission and then moves through the water system before entering the lake. Once in the lake, the mercury is transformed by sediment-dwelling bacteria into methyl mercury, which has a high tendency to bioacculumate in aquatic life.[5] Even now, the State Health Department advises staying clear of eating any fish that come out of the Lake. In addition, through biomagnification, the methyl mercury has made it’s way up the food chain and has been found in bats and birds surrounding Onondaga Lake area. Researchers found that the Spotted-Sand piper was the most affected bird.[6] The levels of mercury found in the animals is so high that only about 20% of all birds’ chicks survive. Furthermore, scientists have reasons to believe that the mercury poisoning will continue to work its way up the food chain unless direct action is taken.

Remediation Efforts: The Upstate Freshwater Institute has been working to prevent the mobilization of methyl mercury from the deep sediments of the Lake. To do so, they have been adding a common agricultural fertilizer, calcium nitrate, solution to the bottom on the lake, which has been successful in lowering the concentration of mercury in fish dramatically.[7] In addition, Honeywell International has been working since 2012, 24 hours a day, 6 days a week, between April and November on dredging the contaminated mud on the bottom of the lake. Earlier this summer, Honeywell attorneys said that there were 800,000 cubic yards of dredging to complete and they estimated being able to complete this amount by the end of the season in 2014. The cost of such efforts is estimated at $451 million.[8] The Metropolitan Syracuse Wastewater Treatment Plant, which dumps about 20% of the water that goes into Onondaga Lake, has spent millions of dollars on making sure that there is no further lake pollution. Although major progress has occurred on the mercury levels on Onondaga Lake. It takes millions of dollars of remediation efforts to fix the polluted ecosystem and years for the biomagnification effects to resolve themselves.[9] has been successful in lowering the concentration of mercury in fish dramatically.[10]

Current Remediation Techniques


Although the EPA is working with the National Institute of Standards and Technology to reduce mercury use and pollution, there are still a number of already contaminated areas that are being remediated now.[11]
Nitrate Immobilization: The use of calcium nitrate to prevent methyl mercury from moving throughout bodies of water.[12]
Dredging: Mercury containing sediments are removed or dug up from the lake bottom.[12]
ISMS (In Situ Mercury Stabilization): Developed by Brookhaven researchers, the ISMS treats and removes mercury content from the soil, sludge, and other industrial waste; therefore stopping mercury from entering the water source.[13]
Thermal desorption: This involves heating the contaminated soil to high temperatures so that the mercury will vaporize away and can be separated from the soil.[13]

CBP4


The transport protein being utilized for our project is the calmodulin-binding protein CBP4 from Nicotiana tabacum. This protein is structurally similar to non-selective membrane channel proteins from other eukaryotes and has been shown to confer nickel tolerance and lead hypersensitivity.[1] Transgenic plants overexpressing NtCBP4 were found to have increased uptake of Pb2+ ions into cells, likely leading to the increased toxicity.[1] While it has been suggested that NtCBP4 could possibly be used for bioremediation purposes and other attempts have been made at lead removal from water using genetically engineered organisms, to the best of our knowledge no attempt has been made at utilizing NtCBP4 for precisely this purpose.[1],[2],[3]. We believe that the specificity of this transport protein for lead and its readily available sequence make it an ideal candidate for bioremediation.

References


  1. Arazi, T., Sunkar, R., Kaplan, B., & Fromm, H. (1999). A tobacco plasma membrane calmodulin-binding transporter confers Ni2 tolerance and Pb2 hypersensitivity in transgenic plants. The Plant Journal, 171-182
  2. Song, W., Sohn, E., Martinoia, E., Lee, Y., Yang, Y., Jasinski, M., Forestier, C., Hwang, I., & Lee, Y. (2003). Engineering tolerance and accumulation of lead and cadmium in transgenic plants. Nature Biotechnology, 914-919.
  3. Eapen, S., & Dsouza, S. (2004). Prospects Of Genetic Engineering Of Plants For Phytoremediation Of Toxic Metals. Biotechnology Advances, 97-114.
  4. "Public Health - Seattle & King County." Lead and Its Human Effects. King County Government, n.d. Web. 15 Oct. 2014.
  5. "Pathophysiology and Etiology of Lead Toxicity ." Pathophysiology and Etiology of Lead Toxicity. Medscape, n.d. Web. 15 Oct. 2014.
  6. "Consumer Factsheet on Lead in Drinking Water." Home. Environmental Protection Agency, n.d. Web. 15 Oct. 2014.
  7. "Why Lead Used to Be Added To Gasoline." Today I Found Out RSS. N.p., n.d. Web. 15 Oct. 2014.
  8. Schwartz, Joel. "Low-level lead exposure and children′ s IQ: a metaanalysis and search for a threshold." Environmental research 65.1 (1994): 42-55.
  9. "CPSC Finds Lead Poisoning Hazard for Young Children in Imported Vinyl Miniblinds." U.S. Consumer Product Safety Commission. US Consumer Product Safety Commission, n.d. Web. 15 Oct. 2014.
  10. "Lead Induced Encephalopathy: An Overview." International Journal of Pharma and Bio Sciences 2.1 (2011): 70-86. Web. http://ijpbs.net/volume2/issue1/pharma/_6.pdf.
  11. McCartor, A., & Becker, D. (2010). Blacksmith Institute's World's Worst Pollution Problems 2010. Retrieved from: http://www.worstpolluted.org/files/FileUpload/files/2010/WWPP-2010-Report-Web.pdf