This sounds like the stuff of comic books but it’s real. Designer Bacteria Can Heal Cracks in Concrete Buildings
The genetically modified microbe has been programmed to swim down fine cracks in concrete and once at the bottom it produces a mixture of calcium carbonate and a bacterial glue. This glue combines with the filamentous bacterial cells, ultimately hardening to the same strength as the surrounding concrete and essentially “knitting” the building back together. [Source, LiveScience, Designer Bacteria Can Heal Cracks in Concrete Buildings]
