Bacteria are useful for myriad applications. Delft University of Technology's Henk Jonkers has recently shown that water-activated bacteria, when worked into concrete, act like osteoblasts do in bones, allowing the concrete to "heal" itself and patch up small cracks, reports New Scientist's Kate McAlpine. Such adjustments to concrete could save cities and towns a lot of time and money when fixing their infrastructure. "Jonkers thinks the solution is to fight nature with nature: he suggests combating water degradation by packing the concrete with bacteria that use water and calcium lactate 'food' to make calcite, a natural cement," McAlpine says.