The Vape, the Mouth, and the Mycobiome: A Comparative Metagenomic Analysis

Electronic nicotine delivery systems (ENDS), including e-cigarettes, are increasingly marketed as safer alternatives to combustible tobacco, yet their effects on oral health remain underexplored. Although the role of ENDS in creating dysbiotic oral bacterial communities is documented, effects on the oral mycobiome remain underexplored. This study compared the subgingival fungal communities of 123 periodontally and systemically healthy e-cigarette–only users, smokers, dual users, former smokers, and never-smokers using whole-genome shotgun sequencing for functional profiling. Taxonomic assignment using Kraken 2 and the PlusPF database identified 98 fungal taxa, and functional annotation with the Kyoto Encyclopedia of Genes and Genomes identified 2,960 fungal genes. Cross-domain bacterial–fungal interactions were interrogated using a correlation threshold of | r | ≥ 0.7 and P ≤ 0.001. E-cigarette users demonstrated a significantly higher α-diversity than smokers and never-smokers did ( P < 0.001; P < 0.005) and a mycobiome enriched with Candida albicans , Aspergillus oryzae , and Schizosaccharomyces pombe . Functional profiling revealed enrichment of genes encoding or DNA repair, xenobiotic degradation, membrane transport, and stress response. The mycobiome of dual users and former smokers using e-cigarettes did not differ from that of e-cigarette users. Cross-kingdom networks identified 5- to 10-fold higher bacterial–fungal connectivity in e-cigarette users, with fungi capable of enhanced stress tolerance, DNA repair capacity, and metabolic adaptability acting as network anchors. Our data support an association between e-cigarette use and remodeling of the oral mycobiome and microbiome, driven by enhanced polymicrobial interactions and increased functional complexity, suggesting that assumptions regarding the biological neutrality of e-cigarette aerosols warrant further investigation.