(2006). Three of nine auxiliary loci ETR-B, Mtub29 and Mtub34 (Supply et al., 2006) were not included in this study because they were previously shown to be monomorphic in ST125 strains

(Valcheva et al., 2008b). The amplicons were evaluated on 1.5% standard agarose gels using a 100-bp DNA ladder (GE Healthcare). The H37Rv strain was run as an additional control of the performance of the method. Size Compound Library datasheet analysis of the PCR fragments in 1.5% agarose gels and assignment of the VNTR alleles were carried out using totallab tl100 software (Nonlinear Dynamics Ltd, UK) and by comparison with correspondence tables kindly provided by Philip Supply. Some PCR reactions were repeated and allele scoring was performed by an independent analysis by two technicians. Analysis of the IS6110 element specific for the LAM genetic family was performed as described previously (Marais et al., 2006). In brief,

a 205-bp band indicates a LAM strain due to the presence of an IS6110 element BGB324 order in a specific site in the genome, whereas a 141-bp band indicates a non-LAM strain lacking the IS6110 element in this site. To minimize the risk of laboratory cross-contamination during PCR amplification, each procedure (preparation of the PCR mixes, the addition of the DNA, the PCR amplification and the electrophoretic fractionation) was conducted in physically separated rooms. Negative controls (water) were included to control for reagent contamination. Cepharanthine NJ and UPGMA trees were built using the paup 4.0 package (Swofford, 2002) and minimum spanning tree – using the PARS program of the phylip 3.6 package (Felsenstein, 2004). At present, the mechanism of evolution of VNTR loci in M. tuberculosis

is not completely understood; for this reason, similar to other studies, VNTR alleles were treated as categorical variables, i.e. any change in a locus (gain or loss of any number of repeats) was considered equally probable. The search for historical links between the areas targeted in this work was carried out by searching Google (http://www.google.com/), Entrez Pubmed (http://www.ncbi.nlm.nih.gov/sites/entrez) and the History Cooperative (http://www.historycooperative.org/) search resources using the keywords ‘human migration,’‘tuberculosis,’‘history,’‘phylogeography,’‘coevolution’ as well as relevant geographic names used alone and in combination. This was followed by further sorting and mining of the large body of the retrieved information, and, if necessary, an additional search using more specific keywords covering bilateral relations between particular regions and countries. Although this method is neither exhaustive nor quite systematic, a quantitative approach to comprehensively study large events in human history still does not exist, to the best of our knowledge.