Growing Indoor Environmental Infrastructure: Active Green Wall Growth Media Design Impacts Substrate Microbial Diversity with Implications for Pollutant Metabolism and Human Health

Urban inhabitants spend upwards of 90% of their time indoors where building design and infrastructure impacts air quality, microbiome diversity, human exposure, and health outcomes. Active green infrastructure designed to improve indoor environmental quality by drawing air through photosynthesizing plants and metabolically diverse rhizospheres have developed substantially since the 1970s, however further study is required: (1) although nascent evidence illustrates human microbiome alteration (and associated health benefits) related to exposure to green wall systems, the mechanism(s) of diversification have not yet been established, (2) microbial metabolism and airborne chemical dynamics are extraordinarily complex and hypotheses pertaining to rhizosphere microorganisms metabolizing pollutants require more attention. To begin exploring these areas, we applied a shotgun metagenomic approach to quantify microbial diversity and establish preliminary metabolic profiles within active green wall modules across a range of growth media and plant selections. Results indicate that fundamental design decisions, including hydroponic vs. organic growth media, support rhizosphere microbiomes with distinct diversity and metabolic profiles which may impact green wall system performance. While not yet fully understood, the described relationships indicate fundamental green infrastructure design choices represent an opportunity to grow indoor microbial diversity and metabolisms with potential benefits for human pollutant exposure and health outcomes.