Early research from the University of Minnesota Twin Cities (U of M) potentially brings a new category of adaptive construction materials a little closer to consumers. Engineered living materials that combine the strength of building materials with the responsiveness of living systems would revolutionize construction and maintenance. Examples are self-healing concrete, material that reproduces to fill cracks and paint that changes color in response to the presence of a particular chemical. Such innovations would have wide-ranging economic and environmental implications.

The U of M researchers from the College of Biological Sciences have shown how to turn a common element of construction materials, silica, into a material that is self-assembling, dynamic and resilient.

Current efforts to produce engineered living materials rely on adding a living component such as engineered bacteria into a material, but have not succeeded in producing a material that survives outside of the lab. The goal is a product that can grow, self-organize and self-heal in real-world applications.

The researchers used Bacillus subtilis, a well-studied benign bacteria, because it goes dormant in unfavorable conditions and still flourishes in favorable conditions. This ability makes it a good candidate for use in shelf-stable, easily activated products. The team engineered the bacteria and studied the best way to integrate it into the silica structure.

"The first time we saw that the bacteria and the silica were cross-linking and forming a rigid material was pivotal. At that moment, we knew it was working," said Claudia Schmidt-Dannert, a professor in the Department of Biochemistry, Molecular Biology and Biophysics who led the research team.

The research, published in Nature Communications, provides a framework for the design of novel engineered living materials for coatings and plasters. "We're now interested in going beyond silica, using different cells -- maybe even multiple cell types -- to develop novel engineered living materials for a range of applications," said Schmidt-Dannert.

The research, funded by the Department of Defense -- Defense Advanced Research Project Agency -- Engineered Living Materials Program (Contract number HR0011-17-2-0038), has potential beyond building materials for biomedical and other applications.