Post-medieval Latvian oral microbiome in the context of modern dental calculus and modern dental plaque microbial profiles.

Recent advantages in paleomicrobiology provides an opportunity to investigate the evolution of the oral microbial ecologies. Here, we investigated microbial composition and functional profiles of modern dental plaque, modern dental calculus, and historic dental calculus samples retrieved from archaeological human remains from post-medieval Latvia dated 16th - 17th century AD.Metagenomic data were generated by high-throughput sequencing. Calculus and plaque samples formed separate clusters based on bacterial phyla, species and metabolomics profiles. Historic dental calculus expressed significantly greater bacterial diversity in comparison with modern dental calculus and modern dental plaque samples. Several differentially abundant bacterial taxons were identified in the sample groups on both the phylum and species levels. No significant differences within historic samples grouped based on sex, age, presence/absence of caries, and lifestyle were observed. Functional profiling revealed that the majority of identified pathways belonged to the essential metabolic processes. While the majority of pathways were shared, the increased presence of several sugar derivative metabolism pathways in modern oral microbiota metabolic profiles was detected. In conclusions, higher microbial diversity of post-medieval calculus samples and the presence of differentially abundant bacterial taxons probably indicate changes related to the postindustrial lifestyle and dietary shifts.