Abstract
E-cigarettes have emerged as an exposomal factor of great concern to human health. We aimed to test the hypothesis that e-cigarette aerosol is metabolized in the oral cavity by the indigenous microbiome, leading to structural and functional alterations in oral biofilms. We combined untargeted metabolomic analysis of in vitro commensal-rich and pathogen-rich microcosm communities with metatranscriptomics, and fluorescent microscopy, and verified the results in human samples. Spectral deconvolution of 4,215 peaks identified 969 exposomal and endogenous metabolites that mapped to 23 metabolic pathways. Aerosol characteristics and biofilm composition affected metabolite profiles. Metabolites generated by commensal-rich biofilms contained antimitic, anti-fungal and anti-bacterial compounds, while pathogen-rich biofilms metabolized nicotine-containing aerosol using the pyridine and pyrrolidine pathways. Both communities generated endogenous metabolites that mapped to quorum sensing functions. Several of these metabolites were verified in the saliva of current, never, and former smokers who vape. Metatranscriptomics revealed upregulation of xenobiotic degradation, capsule, peptidoglycan, and glycosaminoglycan biosynthesis in commensal-rich communities, while genes encoding organic carbon-compound metabolism, antimicrobial resistance and secretion systems were over-expressed in pathogen-rich biofilms. Topographical analysis revealed an architecture characterized by low surface-area to biovolume ratio, high biomass, and diffusion distance only in commensal-rich biofilms. 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. These findings explain the higher incidence of dental caries, gingival inflammation, and antimicrobial resistance observed in vapers.