Conclusion
We propose a new conceptual framework for urban microbial ecology that will help focus research questions and advance knowledge about urban microbial communities and ecosystem functioning. By identifying key drivers, we provide a path forward to link human actions with changes in the soil microbiome. Feedback loops connect microbes back to human society through the provisioning of environmental goods and harms, which brings attention to microbial consequences for human wellbeing. We argue that microbial ecologists and biogeochemists should take advantage of urban ecosystems for future study. Not only do microbial communities represent convenient systems for fundamental research on urban biogeochemistry, microbiomes could also play a role in creating healthier and more sustainable cities. Overall, urban ecosystems deserve more attention from microbial ecologists, and urban ecology would benefit from a greater focus on microbes.