Moisture and material shape microbial communities in the built environment through disturbance–productivity relationships

Abstract The built environment houses diverse microbial communities whose diversity and composition differ among building materials and environmental conditions. Ecological theory makes predictions about how productivity and diversity shape communities, and experiments in the built environment provide an opportunity to test these. We manipulated moisture (constant or repeated wet–dry cycling) on three common building materials to test predictions about alpha and beta diversity. The most productive material (oriented strand board) supported the highest bacterial alpha and beta diversity, and these diversity levels were reduced by repeated drying disturbances. Diversity patterns for fungi were more variable, with the highest alpha diversity on low–moderate productivity material (gypsum wallboard). Fungal beta diversity was reduced by disturbance on high-productivity material, but increased on the other materials. These patterns were driven largely by members of Bacillaceae, Sphingomonadaceae, and Aspergillaceae that reached high abundances in some treatments. Differences between bacteria and fungi may be due to the scale-dependence of productivity–diversity relationships. Together, these results indicate that disturbances can interact with building materials, in some cases leading to variation in community composition that makes it difficult to predict the conditions under which microorganisms with potential importance to health and safety will occur. Importance The built environment—the homes, workplaces, vehicles, and other spaces where people spend most of their time—contains an enormous diversity of microorganisms with significance for human wellbeing, yet we know little about the factors shaping these microbial communities. We found that patterns of wetting and drying that mimic indoor leaks on common building materials affects the diversity of bacteria and fungi growing on the materials. But the identity of these microorganisms differed from one building material to another, and this was especially variable with wetting and drying. This means that common disturbances that lead to microbial growth in homes and offices can make it difficult to predict which microbes, including those that represent health threats to people, will occur in the built environment.