Excavation of agricultural topsoils traditionally used in city landscaping implies strong environmental impacts and a rarefaction of peri-urban fertile soils. The construction of fertile technosols in a circular economy approach using urban wastes is an attracting alternative to such unsustainable practices. However, these soils have specific characteristics, such as rapid pedogenesis and strong influence of parental materials, that conventional agronomic indicators may overlook. Moreover, considering global warming and increase of urban population, their capacity to adapt to urban environment remains a key aspect and may require further engineering processing. To address these two issues, microorganisms are excellent models, as they are acknowledged to respond more rapidly to environmental changes and to show greater adaptability. During this presentation, I will expose the results obtained from a long term monitoring of constructed technosols in realistic conditions and their responses to extreme drought events in controlled climatic chambers.