Students from Cambridge University, in England, engineered bacteria to produce pigments in all colors of the rainbow (shown above) as part of the International Genetically Engineered Machines Competition at MIT. Credit: Mike Davies

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.

UC San Diego bioengineers have created the first stable, fast, and programmable genetic clock that reliably keeps time by the blinking of fluorescent proteins inside E. coli cells. The clock's blink rate changes when the temperature, energy source, or other environmental conditions change. Shown here is a microfluidic system capable of controlling the environmental conditions of the E. coli cells with great precision--one of the keys to this advance. Credit: UC San Diego Jacobs School of Engineering

A molecular timepiece that ticks away the time with a flash of fluorescent protein could provide the basis for novel biosensors. The clock, or synthetic gene oscillator, is a feat of synthetic biology--a fledgling field in which researchers engineer novel biological "parts" into organisms.

To create the clock, scientists genetically engineered a molecular oscillator composed of multiple gene promoters, which turn genes on in the presence of certain chemicals, and genes themselves, one of which codes for a fluorescent protein. When expressed in E. coli bacteria, the feedback system turns the fluorescent gene on and off at regular intervals.

The clock's oscillations can be tuned by the temperature at which the E. coli are grown, the nutrients they are fed, and specific chemical triggers. According to a paper published today in Nature, the fastest oscillations that the scientists have recorded so far are about 13 minutes.

"The on-off frequency could potentially be used to determine the level of some toxic chemical in the environment," says Jeff Hasty, a bioengineer at UC San Diego, who led the project. "One could make simple modifications so that it responded to other chemicals or sugars."

According to a press release from UC San Diego,

One next step is to synchronize the clocks within large numbers of E. coli cells so that all the cells in a test tube would blink in unison. "This would start to look a lot like the makings of a fascinating environmental sensor," said Jeff Hasty, a UC San Diego bioengineering professor and senior author on the Nature paper. Researchers in his lab have also developed sophisticated microfluidic systems capable of controlling environmental conditions of their E. coli cells with great precision. This enables the bioengineers to track exactly what environmental conditions affect their clocks' blink rates.