Microbial diversity was broadly compared across three unique built-environment study sites for 16S rRNA amplicon and shotgun metagenome sequencing. Microbial diversity was broadly compared across three unique built-environment study sites for 16S rRNA amplicon and shotgun metagenome sequencing. (a) Microbial richness of 16S rRNA amplicon data was calculated for various sample types within the built environment and organized by human exposure (H, high human exposure; M, medium human exposure; L, low human exposure). LBM, low biomass, indicates the kit testing controls from the Mobio Powermag kit. Beta diversity PCoA plots of weighted UniFrac distances of 16S rRNA amplicon (c) and Bray-Curtis distances of shotgun metagenomic samples (d) demonstrate study-specific microbial communities. The floor samples within the three built environments are solid spheres in the 16S rRNA amplicon plot (c), while other samples are transparent. (d) Heatmap depicting the top 464 of the 16,417 most abundant sOTUs across the 438 samples that passed QC. Floor samples are indicated by a line to demonstrate the similarity and differences of microbes on the floors of the three built environments. Jeremiah J. Minich et al. mSystems 2018; doi:10.1128/mSystems.00218-17