Abstract
Cigarette smoking affects the oral microbiome, which is related to various systemic diseases. While studies that investigated the relationship between smoking and the oral microbiome by 16S rRNA amplicon sequencing have been performed, investigations involving metagenomic sequences are rare. We investigated the bacterial species composition in the tongue microbiome, as well as single-nucleotide variant (SNV) profiles and gene content of these species, in never and current smokers by utilizing metagenomic sequences. Among 234 never smokers and 52 current smokers, beta diversity, as assessed by weighted UniFrac measure, differed between never and current smokers (pseudo-F = 8.44, R2 = 0.028, p = 0.001). Among the 26 species that had sufficient coverage, the SNV profiles of Actinomyces graevenitzii, Megasphaera micronuciformis, Rothia mucilaginosa, Veillonella dispar, and one Veillonella sp. were significantly different between never and current smokers. Analysis of gene and pathway content revealed that genes related to the lipopolysaccharide biosynthesis pathway in Veillonella dispar were present more frequently in current smokers. We found that species-level tongue microbiome differed between never and current smokers, and 5 species from never and current smokers likely harbor different strains, as suggested by the difference in SNV frequency.
Highlights
Cigarette smoking is associated with many oral diseases such as periodontitis and oral cancer[1]
When the input was the relative abundance of all the species presented in samples, the performance was 0.745 [0.097]. These results indicated that current and never smokers can be discriminated by the singlenucleotide variant (SNV) frequency or gene presence table of Veillonella dispar, one of Veillonella sp, and Actinomyces graevenitzii, which suggested these species within the oral microbiome of current and never smokers have distinct SNV frequency or gene presence frequency characteristics
This study explored the species-level bacterial composition, SNV profile, and gene content of species in the tongue microbiome, with particular focus on the relationship with cigarette smoking
Summary
Cigarette smoking is associated with many oral diseases such as periodontitis and oral cancer[1]. A large study, conducted by Wu et al, indicated that anaerobic bacteria favor the oral environment in smokers, and that aerobic bacteria were less abundant[6]. They revealed that the functional metagenomic profile, which included the degradation of certain toxic compounds contained in cigarettes, differed between current and never smokers. There are few studies that investigated differences in singlenucleotide variant (SNV) profiles and gene content per species in the oral environment across smoking status, which cannot be explored by amplicon sequencing. Specieslevel differences of diversity and abundance, as well as SNV profiles and gene content of the bacterial species, were investigated across the smoking status
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