Longitudinal Analysis of Bacterial Communities in Two Types of Concrete Cylinders

Concrete is the most commonly used building material in the world. From a biological perspective, it is an extreme environment, with high alkalinity and salinity while also prone to large fluctuations in water content and temperature. Concrete thus provides an opportunity to study extremophiles in a common environment. The bacteria involved in acid-catalyzed corrosion of concrete sewers have previously been studied. However, little is known about bacteria in and on concrete under more ordinary conditions such as those experienced by buildings and roads, or how and why their microbial communities change over time. Here, bacterial communities are observed for two years in two types of concrete cylinders, allowing for longitudinal analysis of the taxa present and comparison between the two series. The bacterial communities in and on concrete are broadly similar to those found on other saline surfaces, and in certain aerosols and soils. Analysis of these concrete cylinder series has revealed seasonal variation in the microbial communities, as well as potential bacterial bioindicators of the concrete-degrading alkali-silica reaction, facilitating the development of a rapid assay for this reaction.