Urban greenspaces harbour distinct plasmid communities enriched in heavy metal resistance and competitive traits in...

Plasmids drive horizontal gene transfer, a fundamental mechanism for soil bacterial evolution and antibiotic resistance emergence. In arid regions, the transformation of natural soils into urban greenspaces introduces dramatic environmental changes that influence the adaptive strategies of soil micro-organisms. Additionally, urban greenspaces can act as interfaces of antibiotic resistance spread between environmental and human microbiomes. Here, we inferred plasmids from soil metagenomes of urban greenspaces in Tucson, AZ, USA, and nearby natural arid habitats. We found urban greenspaces to select for plasmids that carried genes that confer competitive advantages, including motility, prokaryotic defence and resistance to heavy metals. Notably, urban greenspace plasmids exhibited reduced diversity (genetic and functional variants), which could in turn constrain their adaptability to rapid environmental changes. These findings underscore the importance of plasmids as agents mediating soil microbial adaptation to human activities.