Researchers at Trinity College Dublin have recovered remarkably preserved microbiomes from two teeth dating back 4,000 years. Genetic analyses of these microbiomes reveal major changes in the oral microenvironment from the Bronze Age to today.

The study, carried out in collaboration with archaeologists from the Atlantic Technological University and the University of Edinburgh, was published Molecular Biology and Evolution. The authors identified several bacteria linked to gum disease and provided the first high-quality ancient genome of Streptococcus mutans, the major culprit behind tooth decay.

While S. mutans is very common in modern mouths, it is exceptionally rare in the ancient genomic record.

The sampled teeth were part of a larger skeletal assemblage excavated from Killuragh Cave, Co. Limerick, by the late Peter Woodman of University College Cork. While other teeth in the cave showed advanced dental decay, no cavities were visible on the sampled teeth. However, one tooth produced an unprecedented amount of S. mutans DNA, a sign of an extreme imbalance in the oral microbial community.

“We were very surprised to see such a large abundance of S. mutans in this 4,000-year-old tooth,” said Dr Lara Cassidy, an assistant professor in Trinity’s School of Genetics and Microbiology, and senior author of the study, “It is a remarkably rare find and suggests this man was at a high risk of developing cavities right before his death”.

The team also found evidence to support the “disappearing microbiome” hypothesis, which proposes modern microbiomes are less diverse than those of our ancestors. This is cause for concern, as biodiversity loss can impact human health.

Very few full genomes from oral bacteria have been recovered prior to the Medieval era. By characterising prehistoric diversity, the authors were able to reveal dramatic changes in the oral microenvironment that have happened since.

From: https://www.sciencedaily.com/releases/2024/03/240327124735.htm