Abstract
Dental calculus (mineralised dental plaque) preserves many types of microfossils and biomolecules, including microbial and host DNA, and ancient calculus are thus an important source of information regarding our ancestral human oral microbiome. We used genetic data to taxonomically characterise the dental calculus microbiome from 20 ancient human skeletal remains originating from Trentino-South Tyrol, Italy, dating from the Neolithic (6000–3500 BCE) to the Early Middle Ages (400–1000 CE). We found a high abundance of the archaeal genus Methanobrevibacter in the calculus. However, only a fraction of the sequences showed high similarity to Methanobrevibacter oralis, associated with periodontitis and the only described Methanobrevibacter species in the human oral microbiome so far. To further investigate the diversity of this genus, we used de novo metagenome assembly to reconstruct 11 Methanobrevibacter genomes from the ancient calculus samples. Besides the presence of M. oralis in one of the samples, our phylogenetic analysis revealed two hitherto uncharacterised oral Methanobrevibacter species. The study thus suggested a possible shift in the human oral microbiome member Methanobrevibacter over the last millennia. We now aim to incorporate more recently published dental calculus samples to the analysis which will extend the analysis to an even broader range of geographical locations and time periods. This will allow us to further explore microbial diversity and evolution of this potential dental pathogen over the course of human history.