Cigarette Butts as an Emerging Urban Habitat Driving Microbial Niche Differentiation

Cigarette butts are common yet overlooked pollutants in urban environments. How this anthropogenic niche shapes microbial life-history strategies and evolutionary mechanisms remains poorly understood, limiting assessments of microbial adaption and urban ecosystem health. However, systematic and multiscale evidence on the ecological effects of cigarette butts on microbial communities remains scarce. Here, we collected cigarette butts, litter, and soil samples from urban parks in 35 Chinese cities and integrated third-generation 16S ribosomal RNA sequencing, metagenomics, and transcriptomics to resolve microbial community composition, functional potential, and evolutionary patterns. The results revealed that microbial communities in cigarette butts were shaped by strong deterministic processes, showed low spatial heterogeneity, and were taxonomically distinct from those in natural niche (i.e., litter) and surrounding soil, with notable enrichment of Proteobacteria, particularly the family Pseudomonadaceae. Functional trait analysis showed that butt-associated communities favored environmental responsiveness and fast-growth strategies, contrasting with metabolism- and resource acquisition-oriented strategies in the litter. Population genomic analysis suggested stronger positive selection in cigarette butt-associated Pseudomonadaceae, while the pure culture experiment provided strain-level evidence that cigarette butt exposure induced the up-regulation of key functional genes in Pseudomonas aeruginosa PAO1. This study demonstrates that cigarette butts, as an emerging ecological niche, reshape microbial community assembly, life-history strategies, and adaptive evolution, offering new insights into microbe-driven evolution on artificial surfaces.