Background: Green renovation is designed to improve the energy efficiency and indoor air quality of a building by modifying physical attributes of the structure. These changes can affect ventilation rates and moisture levels which could, in turn, have an effect on the indoor environmental microbiome.

Aims: Investigate how bacterial diversity differs between green-renovated and non-renovated reference residential buildings using pyrosequencing.

Methods: House dust was collected by floor vacuuming from the living room of 20 apartments before and after green-renovation. DNA extracts from the dust underwent 454 pyrosequencing using the 28F-519R bacterial assay which covers the variable regions V1-V3 on the 16s rRNA gene. Sequence files were queried against a database of high quality bacterial sequences with a BLASTN+ search program and classified at the appropriate taxonomic levels based on identity scores. Results: In non-renovated apartments, the three most abundant phyla in the dust were Proteobacteria, Actinobacteria, and Firmicutes at 39%, 26%, and 20% of the operational taxonomic units (OTUs) observed, respectively. In renovated apartments, the Firmicutes relative abundance increased to 28% of the OTUs (p=0.012), which was offset by decreases in the Proteobacteria and Actinobacteria proportions. The increase in the Firmicutes abundance was driven primarily by increases in the Streptococcus (p=0.001), Lactococcus (p=0.025), and Lactobacillus (p=0.027) genera.

Conclusions: These three genera are representative of bacteria that are part of the commensal human microbiome. Renovation activities appear to permit human-related bacteria to initially account for a larger proportion of the overall bacterial composition compared to the non-renovated condition. The data generated in this pilot study provide a baseline measure of bacterial diversity useful in a longitudinal study investigating the change of indoor bacterial diversity following green renovation.