Fig. 1

Microbial domains of life investigated and experimental approaches adopted to unravel urban soil microbiota in the scientific literature over the last 30 years. (A) Trend of the scientific interest of the different microbial kingdoms over time using the cumulative numbers of citations of each study included in the dataset as a proxy; blue lines indicate the linear regression fitting the data; determination coefficient (R²), P-value and model equation are also showed. (B) Alluvial plot showing the number of studies for each taxa group and profiling approach adopted to investigate the urban soil microbial diversity. The “molecular” category includes all the profiling approaches based on biological macromolecules (nucleic acids, proteins, fatty acids) while “culturomics” includes all those where the isolation of microorganisms on growth media was performed. (C-G) Number of articles that considered (addressed) or not (not addressed) soil pollutants (C), soil physicochemical characteristics (D), microbial biomass (E), enzymatic activity (F), or soil respiration (G) parameters across the different microbial taxa investigated. We categorised as “whole community” all the studies which comprehensively profiled all the domains of microbial life or used respiration- or enzyme-based methods as a proxy for microbiota functionality. See also Table S1 for details on the variables collected