Bacteria Excretions

In Architecture future, bacteria might be what holds our buildings together. Scientists and students are working on genetically modifying a bacteria normally found in soil to repair cracks in concrete. The bacteria that they are calling "BacillaFilla" consists of 3 types of cells; the calcium carbonate producers, the filaments, and the "glue" producers. The cells start working when they come into contact with concrete and the final product is a crack filler that is just as hard as the concrete and has thereby reconnected the structure.
And to make it even more sci-fi, when injected into a crack the bacteria swims down th crack, knows when it's hit the end because of something called "quorum sensing", then it knows when to stop working because of a built-in self destruct gene.
Of course if this other scientist with these students from this other school succeed  in creating "crack-proof" concrete with nanotechnology, then we won't need bacteria poo and all their hard bacteria research will be for naught.