Some bacteria love to live in inhospitable environments that might be excessively hot, dry, or under intense pressure, even concrete. Researchers have now reported that incredibly, bacteria are able to survive in the hard, salty stuff, which has a very basic pH of 12.5, about the same as bleach. Concrete is used in building materials all over the world, and microbes that can live in the stuff might be able to help us predict or repair problems in concrete. The findings have been reported in mSystems.
In this work, the researchers poured 40 samples of two different kinds of concrete, placed them on a roof, and analyzed the genomic content of the samples every six weeks for two years. While there was not much bacteria, the concrete samples had their own microbiomes, said University of Delaware professor Julie Maresca. "There is not a lot of life in concrete; it has a very low biomass," Maresca said.
The researchers determined that the levels of microbes in concrete is affected by weather and seasonality, and that bacteria might be useful indicators of reactions in concrete that eventually cause cracks to form. Some bacteria that produce calcium carbonate might also be useful as a material that might repair holes or cracks. However, research has suggested that these bacteria don't survive in concrete for more than a few months. It may be possible to learn how to lengthen the life of these microbes.
To survive, the microbes may be consuming "the dead bodies of other microbes. If there's nothing to eat, some of them can form spores or form a dormant cell type and do nothing until it rains, then eat as much as they can and go dormant again," Maresca said.
A 2020 report by the Federal Highway Administration noted that over 45,000 bridges in the United States are in poor condition; they are "needing significant maintenance attention, rehabilitation or replacement."
While such an assay has not yet been developed, bacteria might be part of a detection system that can warn us about problems in bridges. "The earlier you can detect a problem, the more time you have to solve a problem before it becomes a real problem," said Maresca, "and since we have all these roads and bridges at risk, we need a way to prioritize them. Which are in dire need and which aren't?"
The researchers think that the bacteria are not causing damage, but their presence can indicate that damage is happening. "Microbes are not eating the foundations. We're hoping to use them for information and potentially to help with repair," Maresca said.