Anthropogenic disturbances, such as urbanization and soil degradation, significantly alter the structure and function of ecological systems, particularly in Mediterranean regions. Technosols, urban soils derived from organic and mineral waste, are increasingly used for urban greening, yet their limited nutrient availability constrains plant productivity. This study examines how Plant Growth-Promoting Bacteria (PGPB) can mitigate the negative effects of environmental disturbances on lettuce growth in both sterilized and non-sterilized Technosols. By comparing sterile and non-sterile conditions, we assessed the impact of three bacterial administration treatments: a Technosol-derived consortium (P3), a halotolerant species Bacillus amyloliquefaciens (R18), and their combination (P4). In the absence of native microbiota – sterilized Technosol - P3 significantly improved of 25% leaf development, of 23% water status, and of 3% photosynthetic efficiency, compared to R18, indicating a strong plant-microbe-soil synergy. However, under non-sterile conditions, competition with indigenous microorganisms reduced the beneficial effects of resulting in increased oxidative stress in plants. Notably, P3 maintained higher specific leaf area with minimal root infection, while R18 delayed leaf senescence and improved physiological resilience. These results highlight the importance of understanding soil microbial dynamics when developing sustainable Nature-Based Solutions to counteract anthropogenic disturbances. Our findings highlight the potential of tailored microbial consortia to restore ecological functions in disturbed urban soils, contributing to more resilient urban farming systems.

Ermenegilda Vitale and Christian Lorenz contributed equally to the research