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A team of scientists in Mexico have sequenced genetic material of Streptococcus mutans, the bacterium responsible for caries in teeth, from ancient populations.
The study by scientists from Universitat Autònoma de Barcelona (UAB) the National Laboratory of Genomics for Biodiversity was published in Proceedings of The Royal Society B on July 23.
The team studied bacteria from the caries samples from 10 individuals from various periods of time from Europe and both pre- and post-colonization America. The oldest case is that of an individual dating from 1200 BC from the burial cave in Montanisell, Catalonia, and the most recent from the UAB collection dates from the beginning of the twentieth century.
They found that the bacteria has accelerated a change in its genetic material over time, and these changes could coincide with dietary changes in humans which could be due to a population expansion.
The study opens up the possibility of providing evidence for the historical relationship between caries and human beings as well as ascertaining the ways in which distinct historical moments may have affected this; additionally, it makes it possible to reconstruct the dietary habits of the ancient population or of the population movements that took place, says a press release by UAB.
"We saw that, in the most recent populations, genetic diversity was greater; to us, this indicates a population-based expansion by the bacterium that may have occurred in parallel with the demographic expansion of humans. We think that this increase took place in the Neolithic. Currently, the oldest individual we have analysed is from the Bronze Age, but we might actually be witnessing the continuation of this process. In the future, we hope to be able to work with even older samples in order to corroborate our hypothesis", says Marc Simón, the study’s principal author.
The analysis of the bacteria in specimen from various periods can help understand the way of life of ancient people. The analysis of such ancient DNA can also be used to identify changes in the lives of their host. For example, due to the fact that S. mutans is, to some extent, maternally transmitted, mitochondrial DNA analysis from this bacterium can be studied to understand the migration patterns of women.
A previous study by an international team from Australia and UK that also studied tartar from ancient skeletons found that the modern ‘good’ oral bacteria is less genetically diverse than that found in ancient populations due to the increase in consumption of processed sugars and carbohydrates, which is why caries-causing bacteria are more common now.
Historically, the incidence of caries also reflects various markers in history, such as the first stage of farming in the American continent when consumption of fruits high in sugar became more common, or the contact between the people of the Old and the New World, especially from before and after AD 1550 when great quantities of sugar and sugar cane begun to get exported from America to Europe. Both events were reflected in a marked increase in the incidence of caries.