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Trypanosoma cruzi has been historically classified as a species with preponderant clonal evolution (PCE). However, with the advent of highly polymorphic markers and studies at geographically reduced scales, the PCE in T. cruzi was challenged. In fact, some studies have suggested that recombination in T. cruzi lineage I (TcI) is much more frequent than previously believed. Further analyses of TcI populations from different geographical regions of Latin America are needed to examine this hypothesis. In the present study, we contribute to this topic by analyzing the population structure of TcI from a restricted geographical area in the Chaco region, Argentina. We analyzed TcI isolates from different hosts and vectors using a Multilocus Sequence Typing (MLST) approach. These isolates were previously characterized by sequencing the spliced leader intergenic region (SL-IR). Low levels of incongruence and well-supported clusters for MLST dataset were obtained from the analyses. Moreover, high linkage disequilibrium was found and five repeated and overrepresented genotypes were detected. In addition, a good correspondence between SL-IR and MLST was observed which is expected under PCE. However, recombination is not ruled out because five out of 28 pairs of loci were incompatible with strict clonality and one possible genetic exchange event was detected. Overall, our results represent evidence of PCE in TcI from the study area. Finally, considering our findings we discuss the scenario for the genetic structure of TcI. [ABSTRACT FROM AUTHOR]

Phylogenetic relationships among major lineages of Trypanosoma cruzi are still debatable. Particularly, it is controversial the origin of two main lineages: TcIII and TcIV. Some authors proposed that these lineages have been the result of an ancient hybridization between TcI and TcII, and this was one of the most accepted evolutionary models in the scientific community for several years. In the present paper we analyse several genomes of T . cruzi in order to examine if there is evidence supporting that TcIII is an ancient TcI/TcII hybrid. Our results show that TcIII is mainly related to TcI and not to TcII and there is few evidence of mosaicism for TcIII. Our results challenge the hypothesis of the ancient TcI/TcII hybridization. [ABSTRACT FROM AUTHOR]

Highlights: [•] We developed a software for multi-locus sequence data analysis (MLSTest). [•] It was designed for typing and clustering in Eukaryotes (particularly diploids). [•] It includes tools to analyze population genetic structure. [•] It includes tools to develop and to optimize typing schemes. [ABSTRACT FROM AUTHOR]

Abstract: A Multilocus Sequence Typing (MLST) scheme was designed and applied to a set of 20 Trypanosoma cruzi stocks belonging to three main discrete typing units (T. cruzi I, V and VI) from a geographically restricted Chagas disease endemic area in Argentina, 12 reference strains comprising two from each of the six main discrete typing units of the parasite (T. cruzi I–VI), and one T. cruzi marinkellei strain. DNA fragments (≅400-bp) from 10 housekeeping genes were sequenced. A total of 4178bp were analyzed for each stock. In all, 154 polymorphic sites were identified. Ninety-five sites were heterozygous in at least one analyzed stock. Seventeen diploid sequence types were identified from 32 studied T. cruzi stocks (including the reference strains). All stocks were correctly assigned to their corresponding discrete typing units. We propose this MLST scheme as provisional, with scope for improvement by studying new gene targets on a more diverse sample of stocks, in order to define an optimized MLST scheme for T. cruzi. This approach is an excellent candidate to become the gold standard for T. cruzi genetic typing. We suggest that MLST will have a strong impact on molecular epidemiological studies of Chagas disease and the phylogenetics of its causative agent. [Copyright &y& Elsevier]

Abstract: Internal and geographical clustering within Trypanosoma cruzi I (TcI) has been recently revealed by using Multilocus Microsatellite Typing and sequencing of the Spliced-Leader Intergenic Region (SL-IR). In the present work, 14 isolates and 11 laboratory-cloned stocks obtained from a geographically restricted area in Chaco Province, Argentina, were analyzed by PCR and sequencing of SL-IR. We were able to differentiate 8 different genotypes that clustered into 4 groups. One of these groups was classified within the formerly described haplotype A and another one within the recently described SL-IR group E. Both were phylogenetically well-supported. In contrast, none of the stocks from the Chaco province were grouped within the cluster previously named haplotype D despite the fact that they shared a similar microsatellite motif in the SL-IR. No evidence of recombination or gene conversion within these stocks was found. On the other hand, multiple ambiguous alignments in the microsatellite region of SL-IR, affecting the tree topology and relationships among groups were detected. Finally, since there are multiple copies of the SL-IR, and they are arranged in tandem, we discuss how molecular processes affecting this kind of sequences could mislead phylogenetic inference. [Copyright &y& Elsevier]

Leishmaniasis is a vector-borne protozoan infection affecting over 350 million people around the world. In Argentina cutaneous leishmaniasis is endemic in nine provinces and visceral leishmaniasis is spreading from autochthonous transmission foci in seven provinces. However, there is limited information about the diversity of the parasite in this country. Implementation of molecular strategies for parasite typing, particularly multilocus sequence typing (MLST), represents an improved approach for genetic variability and population dynamics analyses. We selected six loci as candidates implemented in reference strains and Argentinean isolates. Phylogenetic analysis showed high correlation with taxonomic classification of the parasite. Autochthonous Leishmania ( Viannia ) braziliensis showed higher genetic diversity than L . ( Leishmania ) infantum but low support was obtained for intra- L . braziliensis complex variants suggesting the need of new loci that contribute to phylogenetic resolution for an improved MLST or nested-MLST scheme. This study represents the first characterization of genetic variability of Leishmania spp. in Argentina. [ABSTRACT FROM AUTHOR]

Highlights: [•] A reassessment of Leptospira spp. MLST schemes was performed. [•] The reassessed scheme includes 7 of 13 loci of the most common used MLST schemes. [•] The new scheme strongly support Leptospira species phylogenetic relations. [•] The Argentinian isolates exhibited congruence between allelic profile and serogroup. [•] This 7 loci scheme provide an alternative to typing by serological methods. [Copyright &y& Elsevier]

Genome-based phylogeny has been proposed to be more accurate than phylogeny based in a few genes as MLST-based phylogeny. However, much is not always better. Here we analyzed 368 complete genomes corresponding to 9 bacterial species in order to address intraspecific phylogeny. The studied species were: Burkholderia pseudomallei, Campylobacter jejuni, Chlamydia trachomatis, Helicobacter pylori, Klebsiella pneumoniae, Listeria monocytogenes, Salmonella enterica, Staphylococcus aureus and Streptococcus pyogenes. The intra-specific phylogenies were inferred using the complete genome sequences of different strains of these species and their MLST schemes. A supermatrix approach was used to infer maximum likelihood phylogenies in both cases. The phylogenetic incongruence between the supermatrix-based genome or MLST tree and individual trees (constructed from genome fragments or MLST genes, respectively) was analyzed. In supermatrix-based trees for genomes, most branches showed a high branch support; however, a high number of branches also showed high percentage of topologically incongruent individual trees. Interestingly, genome and MLST trees showed similar levels of incongruence in the phylogeny for each bacteria specie. Both genome and MLST approaches showed that C. trachomatis and S. aureus have a tree-like evolutionary history (low levels of internal incongruence). Instead, B. pseudomallei and S. pyogenes show high levels of incongruence (network-like evolutionary story) probably caused by HGT (horizontal gene transfer). Concluding, our analysis showed that: high branch supports obtained in genome phylogenies could be an artifact probably caused by data size; MLST is valid to address intraspecific phylogenetic structure; and, each species has its own evolutionary history, which could be affected by HGT to different extents. • Genome trees hide extreme incongruence in intraspecific phylogeny in bacteria • Genomic data can cause artifactual statistical support for branches • MLST unveils the same intraspecific genetic structure patterns than genomes [ABSTRACT FROM AUTHOR]