A Genetically Engineered Rainbow of Bacteria

Bioengineering students from around the world converged on MIT this weekend in what has become an annual ritual in synthetic biology–iGEM, the international genetically engineered machines competition. Among the finalists this year were “GluColi”, a new generation of glue made by bacteria, a biological version of an LCD screen made of yeast, and a multicolored menagerie of bacteria that might ultimately become part of a biological system designed to change color in response to toxins or other target compounds, providing an easy-to-read warning system.

By combining snippets of DNA, dubbed biological “parts”, students build microbes designed to perform useful functions, such as producing medicines or detecting toxins. Each year “parts” built for the competition are entered into a biological library, so that next year’s teams can use them to build even more sophisticated machines. As iGEM co-founder and MIT bioengineer Tom Knight explained in a previous piece, “The key idea here is to develop a library of composable parts which we think of in the same way as Lego blocks. These parts can be assembled into more-complex pieces, which in many cases are functional when inserted into living cells.”

Entries into previous years have included yeast designed to produce beer with the health benefits of red wine, sweet-smelling E. coli, a commonly used research bacterium with a vile odor, and probiotic bacteria, like that found in yogurt, designed to fight cavities, produce vitamins, and treat lactose intolerance.

To make multicolored microbes, students from Cambridge University, in England, mined bacterial genomes for pigment-producing genes. They then engineered those genes into the harmless strain of E. coli used in genetic research. Carotinoid enzymes co-opted from Pantoea ananatis, a bacterium that can rot onions, generated red and orange pigments. A gene for melanin, an enzyme from the soil bacterium Rhizobium etli, produces brown. Chromobacterium violacein, a soil and water dwelling microbe offered genes capable of producing shades of violet, green and blue.