Toxic cultures: e-cigarettes and the oral microbial exposome.

We tested the hypothesis that e-cigarette aerosol is metabolized by the indigenous oral microbiome, leading to structural and functional alterations. We combined untargeted metabolomics of in vitro commensal-rich and pathogen-rich biofilms with metatranscriptomics and fluorescent microscopy and verified the results in human samples. Spectral deconvolution of 4215 peaks identified 969 exposomal and endogenous metabolites that mapped to 23 metabolic pathways. The metabolites clustered by both aerosol characteristics and biofilm composition; and several were verified in human saliva of vapers. E-cigarette exposure upregulated xenobiotic degradation, capsule, peptidoglycan biosynthesis, organic carbon-compound metabolism, antimicrobial resistance, and secretion systems. E-cigarette exposure also altered biofilm architecture characterized by low surface-area to biovolume ratio, high biomass, and diffusion distance. In conclusion, our data suggest that bacterial metabolism of e-cigarette aerosol triggers a quorum-sensing-regulated stress response which mediates the formation of dense, exopolysaccharide-rich biofilms in health-compatible communities and antibiotic resistance and virulence amplification in disease-associated communities.