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Auto Tag: Parasitology

April 21, 2020  |  

Insights into the evolution and drug susceptibility of Babesia duncani from the sequence of its mitochondrial and apicoplast genomes.

Babesia microti and Babesia duncani are the main causative agents of human babesiosis in the United States. While significant knowledge about B. microti has been gained over the past few years, nothing is known about B. duncani biology, pathogenesis, mode of transmission or sensitivity to currently recommended therapies. Studies in immunocompetent wild type mice and hamsters have shown that unlike B. microti, infection with B. duncani results in severe pathology and ultimately death. The parasite factors involved in B. duncani virulence remain unknown. Here we report the first known completed sequence and annotation of the apicoplast and mitochondrial genomes of B. duncani. We found that the apicoplast genome of this parasite consists of a 34?kb monocistronic circular molecule encoding functions that are important for apicoplast gene transcription as well as translation and maturation of the organelle’s proteins. The mitochondrial genome of B. duncani consists of a 5.9?kb monocistronic linear molecule with two inverted repeats of 48?bp at both ends. Using the conserved cytochrome b (Cytb) and cytochrome c oxidase subunit I (coxI) proteins encoded by the mitochondrial genome, phylogenetic analysis revealed that B. duncani defines a new lineage among apicomplexan parasites distinct from B. microti, Babesia bovis, Theileria spp. and Plasmodium spp. Annotation of the apicoplast and mitochondrial genomes of B. duncani identified targets for development of effective therapies. Our studies set the stage for evaluation of the efficacy of these drugs alone or in combination against B. duncani in culture as well as in animal models.Copyright © 2018 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.

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April 21, 2020  |  

Large Enriched Fragment Targeted Sequencing (LEFT-SEQ) Applied to Capture of Wolbachia Genomes.

Symbiosis is a major force of evolutionary change, influencing virtually all aspects of biology, from population ecology and evolution to genomics and molecular/biochemical mechanisms of development and reproduction. A remarkable example is Wolbachia endobacteria, present in some parasitic nematodes and many arthropod species. Acquisition of genomic data from diverse Wolbachia clades will aid in the elucidation of the different symbiotic mechanisms(s). However, challenges of de novo assembly of Wolbachia genomes include the presence in the sample of host DNA: nematode/vertebrate or insect. We designed biotinylated probes to capture large fragments of Wolbachia DNA for sequencing using PacBio technology (LEFT-SEQ: Large Enriched Fragment Targeted Sequencing). LEFT-SEQ was used to capture and sequence four Wolbachia genomes: the filarial nematode Brugia malayi, wBm, (21-fold enrichment), Drosophila mauritiana flies (2 isolates), wMau (11-fold enrichment), and Aedes albopictus mosquitoes, wAlbB (200-fold enrichment). LEFT-SEQ resulted in complete genomes for wBm and for wMau. For wBm, 18 single-nucleotide polymorphisms (SNPs), relative to the wBm reference, were identified and confirmed by PCR. A limit of LEFT-SEQ is illustrated by the wAlbB genome, characterized by a very high level of insertion sequences elements (ISs) and DNA repeats, for which only a 20-contig draft assembly was achieved.

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April 21, 2020  |  

Meiotic sex in Chagas disease parasite Trypanosoma cruzi.

Genetic exchange enables parasites to rapidly transform disease phenotypes and exploit new host populations. Trypanosoma cruzi, the parasitic agent of Chagas disease and a public health concern throughout Latin America, has for decades been presumed to exchange genetic material rarely and without classic meiotic sex. We present compelling evidence from 45 genomes sequenced from southern Ecuador that T. cruzi in fact maintains truly sexual, panmictic groups that can occur alongside others that remain highly clonal after past hybridization events. These groups with divergent reproductive strategies appear genetically isolated despite possible co-occurrence in vectors and hosts. We propose biological explanations for the fine-scale disconnectivity we observe and discuss the epidemiological consequences of flexible reproductive modes. Our study reinvigorates the hunt for the site of genetic exchange in the T. cruzi life cycle, provides tools to define the genetic determinants of parasite virulence, and reforms longstanding theory on clonality in trypanosomatid parasites.

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April 21, 2020  |  

Divergent evolutionary trajectories following speciation in two ectoparasitic honey bee mites.

Multispecies host-parasite evolution is common, but how parasites evolve after speciating remains poorly understood. Shared evolutionary history and physiology may propel species along similar evolutionary trajectories whereas pursuing different strategies can reduce competition. We test these scenarios in the economically important association between honey bees and ectoparasitic mites by sequencing the genomes of the sister mite species Varroa destructor and Varroa jacobsoni. These genomes were closely related, with 99.7% sequence identity. Among the 9,628 orthologous genes, 4.8% showed signs of positive selection in at least one species. Divergent selective trajectories were discovered in conserved chemosensory gene families (IGR, SNMP), and Halloween genes (CYP) involved in moulting and reproduction. However, there was little overlap in these gene sets and associated GO terms, indicating different selective regimes operating on each of the parasites. Based on our findings, we suggest that species-specific strategies may be needed to combat evolving parasite communities. © The Author(s) 2019.

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