Analysis of bacterial communities in and on concrete

Bacteria are known to catalyze degradation of concrete, and 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, in part because of difficulty in extracting DNA from inside concrete specimens. Here, we report a method for extraction of nucleic acids directly from hardened concrete. Using this method and classical cultivation methods, we demonstrate that most bacteria in or on concrete belong to two taxonomic groups, that the bacterial diversity is similar on the concrete surface and in the interior, and that many bacteria in and on concrete are related to microbes found in other dry, saline, or alkaline environments. This method lays the foundation for the creation of bioindicators for concrete and may open new avenues for the fields of non-destructive evaluation and assessment of concrete structures.