Global analysis of saliva as a source of bacterial DNA - a potential chronometer for human population and migration studies

智人的历史——一个极具挑战性的研究领域——传统上是通过评估经典的人类DNA标记来探索的。另外，由于与人类相关的细菌具有较高的进化速度，它们在提供人类历史的补充信息方面具有很大的潜力，特别是对于揭示那些太迟而无法用人类DNA标记进行研究的迁徙来说，它们可能特别有用。人类-细菌共同进化的概念已经在幽门螺杆菌中得到了成功的测试，但是它的分析需要胃活检。该项目的目的是验证这样一种假设，即人类唾液微生物群的成员可能作为人类进化的计时器，从而允许人类种群的精细分化。来自全球12个不同民族地区的10名志愿者的唾液样本将被分析。选择的细菌将是口腔链球菌和核梭杆菌，因为它们主要是垂直传播的，很容易在人类唾液中检测到，并且通过定义和完善的标记基因可以区分亚种和克隆簇水平。此外，将进行末端限制性片段长度多态性（T-RFLP）分析，以比较不同样品的微生物群落组成。该项目是微生物学小组和人类学小组之间的独特合作，将建立一个从唾液中识别细菌DNA标记的框架，最终有可能为未解决的人类迁移模式提供新的视角-这是一个具有重大社会，人类学和医学重要性的问题。

The history of Homo sapiens – a highly challenging field of study – has traditionally been explored by assessing classical human DNA markers. Alternatively, because of their higher evolution rate human-associated bacteria principally hold great potential for providing complementary information on human history and could particularly be useful for shedding light on migrations that are too recent to be studied with human DNA markers. The concept of human-bacterial co-evolution has already been successfully tested for Helicobacter pylori however its analysis requires stomach-biopsies. The aim of this project is to test the hypothesis that members of the human salivary microbiota may function as chronometer of human evolution and thus allow a fine-scale differentiation of human populations. Saliva samples from 10 volunteers each from 12 world-wide areas, representing diverse ethnic groups, will be analyzed. The bacteria of choice will be Streptococcus oralis and Fusobacterium nucleatum, because they are primarily transmitted vertically, easily detectable in human saliva, and distinguishable down to subspecies and clonal-cluster level using defined and well-established marker genes. In addition, terminal restriction fragment length polymorphism (T-RFLP) analysis will be performed to compare the microbial community compositions across samples. This project which is a unique collaboration between a microbiology group and an anthropology group will establish a framework for the identification of bacterial DNA markers from saliva with the ultimate potential to provide new perspectives on unsolved human migration patterns – an issue of great social, anthropological, and medical importance.