Examination of Oral Microbiomes from a North American Historic Institutionalized Population Using Metagenomic Sequencing

The human oral microbiome is the total amount of microbial biodiversity present in the oral cavity and, given its relevance to human health and disease, has recently become a focus of study. By analyzing dental calculus, and sequencing the resultant DNA, it is possible to reconstruct and examine the oral microbiomes of past individuals. In this study, dental calculus was sampled from (N=4) skeletons recovered from the cemetery of the mid-19th- 20th, century Mississippi State Asylum in Jackson, MS. During its 80-year operation, the asylum housed 35,000 individuals and had periodic epidemics of tuberculosis, yellow fever, and influenza. Conditions in this asylum were severely lacking; there was overcrowding, in addition to poor and often inadequate nutrition. These four individuals hail from the 1920’s based on dendrochronological dating.The shotgun sequencing and 16S analyses yielded data, revealing the first reconstructed historic oral microbiomes from an institutionalized population. The microbial composition was significantly different from modern post-industrial oral microbiomes, and targeted examinations for opportunistically pathogenic oral bacteria were negative including for the common oral bacterium Streptococcus mutans. It is hypothesized that the restrictive diet and lack of fresh food led to a decreased biodiversity, with the individuals in the MSA lacking the tell-tale pathogenic microbes that are generally present in post-industrial oral microbiomes.