Bioengineered soil

Carolina Ramirez Figueroa, Luis Hernan, and Martyn Dade-Robertson

‘Thinking soil’ made of bacteria could keep buildings from collapsing

It can be quite costly, even catastrophic, when the land under a building subsides. But genetically engineered microbes may one day keep that from happening if researchers in the United Kingdom are successful. Inspired by undergraduates who made a concrete-repairing bacterium—dubbed BacillaFilla—for a synthetic biology competition, a biodesigner and his colleagues have been pushing hard to develop biocement, a material that custom-built soil microbes would produce in response to the changing pressures in soil to help shore up the ground under foundations. Toward that end, the team grew a common gut bacterium in surrogate soil—a “hydrogel” shaped into a cylinder. They subjected the bacteria-laden hydrogel to pressures up to 10 times that experienced at sea level. They identified 122 bacterial genes that increased their activity by at least threefold by the pressure change. The team then modified the bacterial genome so that the regulatory DNA responsible for activating one of these genes was attached to a gene for a protein that glows when produced. The more pressure exerted on the microbe, the more intensely it glows, the scientists will report 29 October at the Association for Computer Aided Design in Architecture conference in Ann Arbor, Michigan. In addition, at the meeting, they will describe a computer program that predicts how the microbe will react to forces, such as water pressure, transferred through soil under a building foundation (as depicted in the illustration). Eventually the researchers plan to replace the glowing protein gene with genes that make biocement, creating a “thinking soil” that will keep buildings safe and be a self-constructing foundation. The effort is part of a growing movement to incorporate biology into architecture, they note.