Bacteria self-assemble in a composite material for civil engineering
The genetically modified microbe (Bacillus subtilis) has been programmed to swim down fine cracks in concrete. Once at the bottom, the resulting clumping of bacteria activates the concrete repair process and the cells differentiate into three types: cells which produce calcium carbonate crystals, cells which become filamentous —acting as reinforcing fibers — and thirdly cells that produce a glue that acts as a binding agent and fills the gap. The whole ultimately hardens to the same strength as the surrounding concrete.
Jennifer Hallinan says that "this could be particularly useful in earthquake zones where hundreds of buildings have to be flattened because there is currently no easy way of repairing the cracks and making them structurally sound."
Regarding potential risks to the environment, the microbe spores start germinating only when they make contact with concrete — triggered by the very specific pH of the material — and they have a built-in self-destruct gene that prevents them from proliferating away from the concrete target.
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