The Mystery of Built Environment Microbiome : Mapping Bacterial Diversity and Translationally Active Abundance in Three Different Office Buildings

The microbiota of the built environment is a combination of human and environmental sources. HEPA filters as an ecological niche for indoor microorganisms are critically important for assessing indoor environmental health. Herein, we used 16S rRNA amplicon sequencing to analyze the bacterial communities in HEPA filters of three office buildings. Chao1, Shannon, and phylogenetic diversity values in the filter of two buildings experiencing the most human interaction was greater than that of the third building experiencing the least interaction. The bacterial source composition varied among buildings; Alphaproteobacteria, Actinobacteria, Bacteroidia, and Bacilli were the predominant. A larger proportion of the bacteria in the HEPA filters of the first two buildings were attributed due to human occupancy. The soil, however, contributed to a higher proportion of the bacteria in the HEPA filters of all buildings. Despite the lack of direct human interaction, filter samples from building 3 contained 15% to 25% human skin-associated taxa. Seven genera were found as the core microbiota of all the buildings, of which Acinetobacter, Enterobacter, Pseudomonas, and Staphylococcus are associated with human health. Additionally, BONCAT-FACS was used to determine the translationally active bacterial population in three buildings. It can detect active cells by tracking the incorporation of amino acids into newly synthesized proteins through bioorthogonal noncanonical amino acid tagging (BONCAT). Approximately 30 to 65 percent of cells of the filter microbiome in all buildings were found to be translationally active. Overall, this study demonstrates sources of indoor contamination in three office buildings and their metabolic state.