URBAN GEOMICROBIOLOGY: MICROBIAL COMMUNITIES IN AND ON CONCRETE (Invited Presentation)

Concrete is the most-used building material in the world, and concrete structures provide unique environments for microbes that live in and on the concrete. When freshly poured, the pH of concrete can be as high as 12.5, and after curing, concrete is not only alkaline, but also dry and salty. Despite this, microbes have long been known to colonize concrete surfaces, where they may catalyze degradation of the concrete, and bacteria have more recently been used to repair micro-cracks in or form protective biofilms on cement mortar. However, the microbial communities in and on concrete under ordinary weathering conditions have not been characterized. We have developed a method for extraction of nucleic acids (DNA) directly from concrete, and demonstrate here that bacterial communities in concrete are dominated by Actinobacteria and Alphaproteobacteria. Microbial diversity on the concrete surface is only slightly affected by deposition from the atmosphere or precipitation, and many bacteria present in and on concrete are related to species found on exposed rocks or in deserts, soda lakes, or hypersaline lagoons: other dry, alkaline, or salty environments. This work lays the foundation for the identification of bioindicators for concrete damage, and establishes isolates that can be characterized to understand how microbes tolerate long-term exposure to the conditions in concrete.