Capturing Metabolically Diverse Soil Microbes Across Urban Farm Settings in the Greater Toronto Area

In this study, we propose a novel approach to characterize the abundance and composition of microbial colonizer pools immigrating into the soil by using sterile traps. These are 24-well no-bottom plates with 0.70 um nylon sheets on both sides to filter the influx of bacterial species into the soil. Traps were deployed and incubated at various locations on an urban landscape gradient in Toronto, Canada, to assess differences in microbial colonizing pools across urban and rural sites. Each well of the trap is filled with sterile soil inoculated with a selection of carbon substrates of different types or with tree litter to assess the metabolic heterogeneity of dispersing microbial pools. Results show that diversity and composition of microbes in the presence of certain carbon source pools vary across an urbanization gradient; however, they are ultimately more sensitive to location than in the presence of other factors. Distinct microbial compositional shifts across carbon pools suggest preferences in resource utilization and, therefore, can be used as a proxy for active functional dynamics within communities. This research will inform sustainable urban agricultural practices by strategically managing urban microbial pools, ultimately fostering sustainable urban development.