Genetic material of caries bacterium
obtained from ancient teeth
13 August 2014
Spanish and Mexican researchers have sequenced genes of tooth
bacterium going back to the Bronze Age and found increased genetic
change in recent times, coinciding with dietary change linked to the
expansion of humanity.
Researchers from the Universitat Autònoma de Barcelona (UAB) and
the Laboratorio Nacional de Genómica para la Biodiversidad (National
Laboratory of Genomics for Biodiversity) in Mexico have, for the
first time, sequenced genetic material from Streptococcus mutans,
one of the principal bacteria that cause dental caries. The increase
in genetic diversity has been produced especially in the fragment of
a gene that codifies a virulence factor known as dextranase.
The research, published in Proceedings of The Royal Society B,
studied the bacterium in eleven individuals from the Bronze Age up
to the twentieth century, in Europe and in both pre- and
post-colonial America. The oldest case is that of an individual
dating from 1200 BC, from the burial cave in Montanisell (Lleida,
Catalonia); the most recent, from the UAB collection, dates from the
beginning of the twentieth century.
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.
Collecting ancient DNA from a tooth sample.
Image source: UAB
“The relationship is well known between the increase in frequency
of caries and the dietary changes that occurred in the Neolithic, or
with the European discovery of America, with the large-scale
introduction of sugarcane to Europe, or the Industrial Revolution,
but what was not known was whether this change happened jointly with
changes at a genetic level is this bacterium”, explains Marc Simón,
trainee researcher in the UAB Biodiversity doctorate and the
article’s principal author.
“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
Assumpció Malgosa, researcher in Biological Anthropology at the
UAB and coordinator of this research, said, “It is important to know
how the gene varied in the past in order to predict models of
evolution for caries virulence, to know whether these changes were a
response brought about in order to adapt better to changing
environments or even to other parts of the human body, such as the
gastrointestinal tract, or if they changed to become resistant when
conditions of hygiene improved, etc. Knowing how they reacted in the
past in different situations can provide us with an idea of how they
will do so in the future in similar circumstances”.
Simón M, Montiel R, Smerling A, Solórzano E, Díaz N,
Álvarez, Sandoval BA, Jiménez-Marín AR, Malgosa A. 2014. Molecular
analysis of ancient caries. Proc. R. Soc. B 20140586.