Tobacco Smoking Correlates with Changes in Relative Abundance of Gut Microbes and Their Inter-Phyla Interactions

Abstract

Smoking tobacco increases the risk of various severe health complications and has been associated with alterations in both the oral and gut microbiomes. E-cigarettes are a novel alternative to smoking cigarettes and have been marketed as a healthier option, but they also carry health risks and have been shown to cause changes to the oral microbiome. A dataset from Stewart et al. was used to compare the microbiome diversity across three groups: tobacco smokers, e-cigarette users, and non-smokers. Univariate regression modelling was first used to determine which demographic or lifestyle factors drive changes in the microbial diversity in the oral and gut microbiome of tobacco smokers and e-cigarette users, and found that only smoking tobacco drives differences in the microbial profile of fecal samples. Furthermore, beta diversity metrics that consider abundance, including Bray-Curtis and weighted Unifrac, identified distinct clustering patterns between tobacco smokers and tobacco non-smokers, suggesting tobacco smoking-driven differences in microbial profile may be associated with the abundance of certain taxa. Taxonomic composition analysis and differential expression sequence analysis revealed that, when comparing tobacco smokers and tobacco non-smokers, there was a decrease in the relative abundance of Firmicutes and an increase in Bacteroidota phyla. Within the Bacteroidota phylum, there was a significant increase in the abundance of Prevotella and a decrease in Bacteroides genera. Co-occurrence analysis and chord diagram visualizations further demonstrated that the decrease in abundance of Firmicutes in tobacco smokers was associated with decreased inter-phyla interactions. This reduced Firmicutes-to-Bacteroidota ratio may predispose individuals to pro-inflammatory gut conditions and reflect a state of dysbiosis. Overall, this study corroborates that tobacco smoking is associated with changes in the gut microbiota, specifically through changes in the relative abundance of taxa and alterations in inter-phyla interactions.