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Toxin sensor made from a 'biobrick' takes bronze in international contest

A biosensor made from a common bacterium that can detect toxic metals in water won the Cornell Genetically Engineered Machines (GEM) student project team a bronze metal at a recent competition.

For the first time, the CU GEM team, formed last year, competed at the international Genetically Engineered Machines (iGEM) competition in late October at Massachusetts Institute of Technology. The student contest, which drew close to 1,200 participants from 110 institutions around the world, required teams to create machines based on biological components, or "biobricks."

The field, called synthetic biology, involves the engineering of complex biological systems. The Cornell students hope the success of their team can bring awareness of the interdisciplinary, relatively new field at Cornell.

Based on the research of Cornell professor of microbiology John D. Helmann, one of the team's faculty advisers, they made the biomachine from a common soil bacterium called bacillus subtilis, which has a built-in mechanism for regulating the concentration of metals inside its cells.

They inserted the DNA code for a fluorescent protein, called a reporter, into the bacillus subtilis genome, so that, when it encountered the toxic metal cadmium, the engineered bacterium would express the fluorescent protein and glow blue. The intensity would be relative to the concentration of bio-available cadmium -- the type harmful to biological systems -- in the sample.

The machine provides a quick and relatively inexpensive way to detect the toxic metal in water for drinking or irrigation, particularly in developing countries where contamination problems are abundant.

Though other methods can detect cadmium, such as atomic absorption spectroscopy, the team feels their machine could be a simpler and less costly alternative.

"Once you have the genetic elements in place and you have your engineered strain, you can just grow it," explained Xing Xiong '10. Their sensor is also tuned to detect only the type of cadmium harmful to humans, whereas other methods are less specific, added Malinka Walaliyadde '12.

The team is recruiting new students, since only three students are returning next year. In just one year, they have achieved official project-team status and won funding from several sources.

The students' effort will further be bolstered by a new course offered for the first time next fall, called Synthetic and Systems Biology, taught by Xiling Shen, assistant professor of electrical and computer engineering.

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Blaine Friedlander