An investigation of the evolutionary history of tuberculosis using ancient DNA

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Tuberculosis (TB) is a re-emerging infectious disease caused by the bacterium Mycobacterium tuberculosis and its close relatives, and it has a long history of affecting humans as shown by both historical data and lesions in skeletal remains. Recent molecular evidence indicates that M. tuberculosis is much older than previously thought, extending over three million years in the Old World and originating in Africa. The goal of this project is to analyze ancient DNA from skeletal samples dating before, during, and after the "Age of Exploration" that show evidence of tubercular bone lesions and integrate these data with data from modern strains of tuberculosis to assess the evolutionary history of tuberculosis and its effects on human history. The researchers will extract DNA from approximately 275 bone samples, test them for the presence of human and tuberculosis DNA, and then sequence the TB DNA. The data generated will be used to examine the relationship between TB strains in the Americas before and after European contact since it is hypothesized that European strains replaced those found in the Americas prior to contact. In addition, the investigators will assess the relationship between Asian (ancient and modern) TB strains and the strains present in the Americas prior to European contact, as well as assess whether the increase in prevalence of tuberculosis during the 17th and 18th centuries in Europe was due to the spread of new strains. Preliminary data indicate that about 17% of the samples contain TB DNA, and that the strains present in the Americas before European contact were different from the strains present today. This research will aid in the understanding of how human migration events and possible changes in the pathogenicity of M. tuberculosis over time have facilitated the spread of tuberculosis.