Molecular analysis of ancient caries

Abstract

An 84 base pair sequence of the Streptococcus mutans virulence factor, known as dextranase, has been obtained from 10 individuals from the Bronze Age to the Modern Era in Europe and from before and after the colonization in America. Modern samples show four polymorphic sites that have not been found in the ancient samples studied so far. The nucleotide and haplotype diversity of this region have increased over time, which could be reflecting the footprint of a population expansion. While this segment has apparently evolved according to neutral evolution, we have been able to detect one site that is under positive selection pressure both in present and past populations. This study is a first step to study the evolution of this microorganism, analysed using direct evidence obtained from ancient remains.

Keywords: Streptococcus mutans; dextranase; neutral evolution; positive selection.

Figure 1.

Median-joining network of the sequences presented in this study. Modern sequences (11 modern strains from Genbank obtained in this study) are: U159 and GS5 (USA), NN2025 and LJ23 (Japan), D4930.1, ATCC 25175 and 5DC8 (England), KK21, KK23 and AC4446 (Germany) and NCTC11060 (Denmark). Ancient samples frequency is in black inside the circles and their names are highlighted in bold, and modern samples frequency is represented in white. (Online version in colour.)