PROBING THE GENETIC POPULATION-STRUCTURE OF TRYPANOSOMA-CRUZI WITH POLYMORPHIC MICROSATELLITES

We describe here the identification of eight polymorphic microsatellit e loci with (CA)(n) repeats in the Trypanosoma cruzi genome based on t he affinity capture of fragments using biotinylated (CA)(12) attached to streptavidin-coated magnetic beads. The presence of two peaks in PC R amplification products from individual clones confirmed that T. cruz i is diploid. Hardy-Weinberg and linkage disequilibrium analyses sugge sted that sexual reproduction is rare of absent and that the populatio n structure is clonal. Several strains, especially those isolated from nonhuman sources, showed more than two alleles in many loci demonstra ting that they were multiclonal. The phylogenetic analysis of T. cruzi based on microsatellites revealed a great genetic distance among stra ins, although the strain dispersion profile in the Wagner network was in general agreement with the species dimorphism found in PCR amplific ation of the divergent region of the rRNA 24S alpha gene.