Microbial and chemical dynamics in cigar tobacco aging driven by spatiotemporal environmental heterogeneity

The natural aging of cigar tobacco leaves is a complex process involving interactions among environmental conditions, microbial community dynamics, and chemical transformations. However, the ecological mechanisms driving microbial succession and chemical changes across different production regions remain poorly understood. In this study, we conducted synchronized aging experiments in four major cigar-producing regions, combining microenvironment monitoring with comprehensive microbial and chemical analyses. Pronounced regional differences in temperature and humidity significantly influenced major chemical traits, including total nitrogen, alkaloids, petroleum ether extracts, and mineral elements. Microbial community structure and diversity also varied significantly across regions and aging stages ( p < 0.05). Random forest regression showed that multiple bacterial and fungal taxa were associated with chemical variation, with fungal community composition and richness exhibiting stronger explanatory power than bacterial diversity. Notably, Fusarium emerged as a representative fungal driver, while bacterial genera such as Massilia and Bacillus displayed significant but relatively weaker associations. Structural equation modeling further revealed that temperature and humidity influenced chemical characteristics indirectly through microbial communities, with bacterial diversity exerting a positive effect and fungal community composition a negative influence ( p < 0.05). Null model indicated that bacterial community assembly was primarily governed by stochastic processes, whereas fungal assembly involved both stochastic and deterministic processes. Overall, these findings provide a mechanistic that connects microenvironmental regulation, microbial community assembly, and chemical evolution, offering insights for region-specific optimization of cigar tobacco aging processes. • Regional temperature and humidity shaped chemical composition of cigar leaves. • Massilia , Solibacillus , Fusarium , and Mortierella contributed to chemical variation. • Fungal structure and richness more influence chemical profiles than bacteria. • Microenvironment affects chemical traits indirectly via microbial communities.