The communities of bacteria that live in our mouths have changed drastically since the Middle Ages, according to a new study of remains buried in a medieval Danish cemetery. And it turns out that some people may have been more predisposed to tooth and gum disease than others, thanks in part to the bacterial communities that lived in their mouths.
Biochemist Rosa Jersie-Christensen of the Novo Nordisk Foundation Center for Protein Research sampled hardened dental plaque, called calculus, from the skeletal remains of 21 Danish men who lived in the village of Tjærby between 1100 and 1450 CE. She and her colleagues chose men for the study because male immune systems tend to have stronger inflammatory responses, which would make it easier to find proteins associated with inflammation.
Overall, the men’s dental health wasn’t great—about what you might expect from a group of medieval villagers. All 21 showed some signs of gum disease, or periodontitis, along with at least minor cavities. Several had lost teeth sometime before their death.
The calculus had preserved thousands of proteins from the men’s bodies, their food, and the bacteria that lived in their mouths. Using mass spectrometry and a database of known proteins, Jersie-Christensen and her colleagues identified 3,761 different proteins in the samples. A few came from food, and others came from the host’s body. About 50 proteins came from blood plasma, and their presence suggests bleeding gums. But the majority of proteins—between 85 and 95 percent—had been produced by bacteria from the microbiome. There were proteins from about 220 different species in all.
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