Nepali oral microbiome follows a gradient of lifestyles from traditional to industrialized

Lifestyle has been demonstrated to play a role in the gut microbiome, primarily due to the varying dietary and environmental components of different lifestyle stages. The role of lifestyle in the oral microbiome remains unclear, as it has been difficult to parse out the impact of confounding geographical and technical factors. Furthermore, comparisons have primarily been across vastly different lifestyles, so we lack insight into when oral microbiome shifts occur in response to lifestyle. Finally, our understanding of the oral microbiome is highly limited to industrialized populations, so it is unknown whether similar lifestyle trends would be observed in both industrialized and understudied traditional populations. Here, we investigate salivary microbiomes of individuals from five different lifestyles across two countries: Nepali Foragers, Nepali Recently Settled (individuals that transitioned from foraging to farming within the last 100 years), Nepali Agriculturalists (individuals that have been farming for at least 300 years), Nepali Expats (individuals that immigrated to the US within the last 20 years), and American Industrialists (European Americans). In our study, we sought to understand the role of lifestyle on overall microbiome diversity, identify microbes that differ between lifestyles, and determine which specific lifestyle factors may be driving differences in the microbiomes. We find that overall microbiome diversity follows the lifestyle trend, in that more different lifestyles have more different oral microbiomes, supporting that lifestyle indeed plays a role in the oral microbiome. When examining specific microbes across lifestyle, Streptobacillus and unclassified Porphyromonadaceae are identified as differentially abundant. Finally, when investigating the lifestyle factors involved, we observe that smoking, environmental, and dietary factors are major components driving the differences in the oral microbiomes, components that have also been found to influence the oral microbiomes of industrialized individuals. Our findings demonstrate how the oral microbiome shifts along the lifestyle gradient and highlight the contributions of several lifestyle factors, underlining the importance of carefully examining the oral microbiome across lifestyles to improve our understanding of the global microbiome.