Cornell iGEM Makes a ‘Safe Bet’ On Monitoring Water Contaminants
Imagine a system capable of continuously monitoring the quality of surrounding water sources and promptly sending out warnings when they appear to be contaminated. Now, imagine having this information readily available over wireless Internet at the slide of a fingertip across the screen of an Android or iPhone. This is precisely what Cornell University Genetically Engineered Machines (iGEM) developed as a solution to counteract the contamination of Canadian water reserves from the excessive mining of oil sands — a cost-efficient, field-deployable biosensor that detects contaminants via an electroactive bacteria. Consisting of a total of 21 members from diverse science majors, Cornell iGEM is a completely undergraduate-run project team that strives to engineer innovative solutions to treat real world problems. The team is split into two collaborative groups, the Wet Lab, which deals directly with the biological aspects of a project and the Dry Lab, which engineers these concepts into a device that makes the biology useful. Their collaborative approach focuses on synthetic biology, a relatively new scientific field that essentially treats cells as “programmable entities.” “In the same way that you can program a computer to perform functions, you can program a cell to accomplish a specific engineered task,” said project manager Dylan Webster ’13, biological engineering. This novel approach to genetic engineering served as the basis behind the team's project, SAFE BET. SAFE BET short for Shewanella Assay for Extended Biomonitoring of Environmental Toxins, was the team’s most recent project in the International Genetically Engineered Machines (iGEM) competition this year. An annual competition with over 200 universities participating, iGEM challenges teams to build and design their own biological systems and operate them in living cells. When brainstorming possible project topics, the Cornell iGEM team focused on a specific environmental concern they wanted to address — oil sands extraction in Alberta, Canada. Oil sands are mixtures of loose sand clay minerals, and water that contain black, dense, viscous forms of unconventional petroleum called bitumen, or tar. Through surface mining and in situ extraction — a technique where heat is used to extract deeper deposits of bitumen to the surface — bitumen is refined into gasoline and diesel. According to the group, this process consumes an abundance of freshwater that results in a buildup of toxic waste called tailings. Tailings consist of mixtures of water, sand, and hazardous contaminants such as arsenic and naphthalene. Both toxins cause adverse health effects; naphthalene is classified as a possible carcinogen by the Environmental Protection Agency (EPA). As these tailings continue to accumulate due to increasing rates of oil extractions, the buildup of excess toxic waste have the potential to leak into groundwater and contaminate streams and water supplies. To help protect drinking water sources from contaminations leaking from tailing ponds and detect arsenic and naphthalene levels, team members turned to a species of electroactive bacteria called Shewanella oneidensis. Shewanella is an ideal organism for the project because of its metal-reduction pathway and its ability to withstand low temperatures. The bacteria, when exposed to arsenic or naphthalene, can produce an electrical output, or current, through electron transfer from cells to metals. “The best way to think about the bacteria is that it’s a way to transduce a chemical signal into an electrical output,” stated Swati Sureka ’15, biological sciences and chemistry, human practices coordinator. The bacteria converts a hard-to-grasp concept, the chemical concentration of a toxin, into a quantifiable electrical output that can be easily interpreted to determine the concentration of any toxin. “We're basically storing our sensor in a body of water, and if arsenic and naphthalene are in the water, our bacteria will sense that and make a current,” said wet lab member Spencer Chen ’13, biological sciences. “Our device detects the current and basically sends this data to anybody with internet access so that they can monitor the water quality at any given time.” Mechanically, the device consists of a reactor with the bacteria and the electronics, which include an electric hardware piece called a potentiostat. The potentiostat sets a potential for the living electrode for the bacteria, a micro-controller which can transmit to the internet and can send out data wirelessly through remote communication, and other circuit materials. The biosensor is housed inside a waterproof, 120-pound pelican case which contains several solar panels which help it recharge its batteries. While inside the biosensor, the Shewanella feasts on a six month supple of bacteria food. Compared to traditional biosensors that use fluorescence, SAFE BET’s use of electroactive bacteria offers two main advantages — lower cost and continuous sampling of water quality. According to the team, traditional biosensors can only offer spot sampling of streams because they can only be deployed for short periods. SAFE BET, on the other hand, offers continuous testing of a water site which provides a more comprehensive overview of the contamination in a river or stream. “If you're spot testing, that means you have to go out to the field, get a sample, and bring it back to the lab to test it,” said wet lab member Caleb Radens ’13, biological sciences. “If a contamination occurs and you spot tested right before that happened or a day after it happened, you might not see that there is a contamination. But if you continuously monitor it, then you know there’s a contamination because you'd always see data.” After a six-month long process that started in mid-April of last year, the Cornell iGEM team, after extensive planning, building, and revising, presented its fully functional prototype, SAFE BET at the iGEM 2012 Americas East Regional Jamboree at Duquesne University. Out of the 43 teams that participated in the East Coast division, Cornell iGEM placed in the top four, and advance onto the iGEM 2012 World Championship Jamboree. At the Worlds Championship, out of the 72 teams that had advanced, Cornell iGEM was one out of only four American universities that placed in the top 16. “It’s amazing to see what a group of undergraduates can accomplish. It’s sometimes hard to get taken seriously because we are a completely undergraduate-run group. We are very autonomous but it is really amazing to see the things that can come of this,” Sureka said. While the competition may have ended for the Cornell iGEM team, there still remains a lot to be done. The success of the initial Safe Bet model presents immense potential for future projects. “Looking into the future, it’d be really cool to develop a platform of sensors that can translate information that is hard to have access to ordinarily, such as biochemical information, and then transduce that into an electrical signal,” Webster said.