Lifestyle Impacts the Oral Microbiome of Classical and Post-Classical Societies in Italy.

OBJECTIVES: The fall of the Roman Empire (476 CE) profoundly affected the lives of its peoples due to the political, administrative, and territorial changes that occurred. The majority of written records of the time focus on the social élite, leaving larger parts of the population understudied. Here, we employ a bioarchaeological approach to understand how differences in lifestyle may be reflected in the oral microbiome of people from different social classes living before and after the fall. MATERIAL AND METHODS: We analyzed shotgun sequencing data from dental calculus, the preserved oral microbiome, of 67 individuals belonging to different social classes from two Classical cemeteries (I-III century CE, Lucus Feroniae and Isola Sacra) and one post-Classical cemetery (IV-VIII century CE, Selvicciola), all located in proximity to the city of Rome, Italy. RESULTS: We detect significant differences in the taxonomic and functional composition of the oral microbiome between the three sites, with the rural town of Lucus Feroniae standing out compared to its two counterparts. Reliable identification of dietary items was not possible. DISCUSSION: The distinct oral microbiome of Lucus Feroniae could reflect differences in general health and subsistence practices, in line with previously published isotopic and morphological data. Its rural position may have mitigated the cyclical food crises that affected the contemporary Isola Sacra and the later community of Selvicciola, buffering it against the nutritional stress observed in these two locations. This finding supports the temporal stability of the dental calculus microbiome while highlighting the impact of lifestyle on the oral microbial communities.