scholarly journals Population genomics of Bacillus anthracis from an anthrax hyperendemic area reveals transmission processes across spatial scales and unexpected within-host diversity

2021 ◽  
Author(s):  
Taya L. Forde ◽  
Tristan P. W. Dennis ◽  
O. Rhoda Aminu ◽  
William T. Harvey ◽  
Ayesha Hassim ◽  
...  
Keyword(s):  
Bacillus Anthracis ◽  
Population Genomics ◽  
Spatial Scales ◽  
Genomic Diversity ◽  
Phylogeographic Structure ◽  
Bacterial Disease ◽  
Significant Finding ◽  
Long Distance ◽  
Genome Wide ◽  
Analytical Approaches

AbstractGenomic sequencing has revolutionized our understanding of bacterial disease epidemiology, but remains underutilized for zoonotic pathogens in remote endemic settings. Anthrax, caused by the spore-forming bacterium Bacillus anthracis, remains a threat to human and animal health and rural livelihoods in low- and middle-income countries. While the global genomic diversity of B. anthracis has been well-characterized, there is limited information on how its populations are genetically structured at the scale at which transmission occurs, critical for understanding the pathogen’s evolution and transmission dynamics. Using a uniquely rich dataset, we quantified genome-wide single nucleotide polymorphisms (SNPs) among 73 B. anthracis isolates derived from 33 livestock carcasses sampled over one year throughout the Ngorongoro Conservation Area, Tanzania, an area hyperendemic for anthrax. Genome-wide SNPs distinguished 22 unique B. anthracis genotypes within the study area. However, phylogeographic structure was lacking, as identical SNP profiles were found throughout the study area, likely the result of the long and variable periods of spore dormancy and long-distance livestock movements. Significantly, divergent genotypes were obtained from spatio-temporally linked cases and even individual carcasses. The high number of SNPs distinguishing isolates from the same host is unlikely to have arisen during infection, as supported by our simulation models. This points to an unexpectedly wide transmission bottleneck for B. anthracis, with an inoculum comprising multiple variants being the norm. Our work highlights that inferring transmission patterns of B. anthracis from genomic data will require analytical approaches that account for extended and variable environmental persistence as well as co-infection.ImportancePathogens transmitted between animals and people affect the health and livelihoods of farmers, particularly in developing countries dependent on livestock. Understanding over what distances these pathogens are transmitted and how they evolve is important to inform control strategies towards reducing disease impacts. Information on the circulation of Bacillus anthracis, which causes the often-lethal disease anthrax, is lacking for settings where the disease is commonplace. Consequently, we examined its genetic variability in an area in Tanzania where anthrax is widespread. We found no clear link between how closely cases were sampled and their genetic similarity. We suspect this lack of congruence is primarily driven by large-scale livestock movements, which control efforts should take into consideration. Another significant finding was the co-occurrence of multiple B. anthracis types within individual hosts, suggesting animals are commonly infected with a mixture of variants. This needs to be accounted for when investigating possible connections between cases.

scholarly journals Genome-wide diversity and global migration patterns in dromedaries follow ancient caravan routes

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Sara Lado ◽  
Jean Pierre Elbers ◽  
Angela Doskocil ◽  
Davide Scaglione ◽  
Emiliano Trucchi ◽  
...  
Keyword(s):  
Demographic History ◽  
Genomic Diversity ◽  
Phylogeographic Structure ◽  
Arid Environments ◽  
Migration Patterns ◽  
Migration Rates ◽  
Global Migration ◽  
Genome Wide ◽  
A Genome ◽  
Scale Population

AbstractDromedaries have been essential for the prosperity of civilizations in arid environments and the dispersal of humans, goods and cultures along ancient, cross-continental trading routes. With increasing desertification their importance as livestock species is rising rapidly, but little is known about their genome-wide diversity and demographic history. As previous studies using few nuclear markers found weak phylogeographic structure, here we detected fine-scale population differentiation in dromedaries across Asia and Africa by adopting a genome-wide approach. Global patterns of effective migration rates revealed pathways of dispersal after domestication, following historic caravan routes like the Silk and Incense Roads. Our results show that a Pleistocene bottleneck and Medieval expansions during the rise of the Ottoman empire have shaped genome-wide diversity in modern dromedaries. By understanding subtle population structure we recognize the value of small, locally adapted populations and appeal for securing genomic diversity for a sustainable utilization of this key desert species.

scholarly journals Population genomics of louping ill virus provide new insights into the evolution of tick-borne flaviviruses

2020 ◽  
Author(s):  
Jordan J. Clark ◽  
Janice Gilray ◽  
Richard J. Orton ◽  
Margaret Baird ◽  
Gavin S. Wilkie ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Molecular Clock ◽  
Population Genomics ◽  
Genomic Diversity ◽  
Past Century ◽  
Evolutionary Analysis ◽  
Clock Rate ◽  
Long Distance ◽  
Louping Ill ◽  
The Uk

AbstractBackgroundThe emergence and spread of tick-borne arboviruses pose an increased challenge to human and animal health. In Europe this is demonstrated by the increasingly wide distribution of tick-borne encephalitis virus (TBEV, Flavivirus, Flaviviridae), which has recently been found in the UK. However, much less is known about other tick-borne flaviviruses (TBFV), such as the closely related louping ill virus (LIV), an animal pathogen which is endemic to the UK and Ireland but which has been detected in other parts of Europe including Scandinavia and Russia. The emergence and potential spatial overlap of these viruses necessitates improved understanding of LIV genomic diversity, geographic spread and evolutionary history.Methodology/principal findingsWe sequenced a virus archive composed of 22 LIV isolates which had been sampled throughout the UK over a period of over 80 years. Combining this dataset with published virus sequences, we detected no sign of recombination and found low diversity and limited evidence for positive selection in the LIV genome. Phylogenetic analysis provided evidence of geographic clustering as well as long-distance movement, including movement events that appear recent. However, despite genomic data and an 80-year time span, we found that the data contained insufficient temporal signal to reliably estimate a molecular clock rate for LIV. Additional analyses revealed that this also applied to TBEV, albeit to a lesser extent, pointing to a general problem with phylogenetic dating for TBFV.Conclusions/significanceThe 22 LIV genomes generated during this study provide a more reliable LIV phylogeny, improving our knowledge of the evolution of tick-borne flaviviruses. Our inability to estimate a molecular clock rate for both LIV and TBEV suggests that temporal calibration of tick-borne flavivirus evolution should be interpreted with caution and highlight a unique aspect of these viruses which may be explained by their reliance on tick vectors.Author SummaryTick-borne pathogens represent a major emerging threat to public health and in recent years have been expanding into new areas. LIV is a neglected virus endemic to the UK and Ireland (though it has been detected in Scandinavia and Russia) which is closely related to the major human pathogen TBEV, but predominantly causes disease in sheep and grouse. The recent detection of TBEV in the UK, which has also emerged elsewhere in Europe, requires more detailed understanding of the spread and sequence diversity of LIV. This could be important for diagnosis and vaccination, but also to improve our understanding of the evolution and emergence of these tick-borne viruses. Here we describe the sequencing of 22 LIV isolates which have been sampled from several host species across the past century. We have utilised this dataset to investigate the evolutionary pressures that LIV is subjected to and have explored the evolution of LIV using phylogenetic analysis. Crucially we were unable to estimate a reliable molecular clock rate for LIV and found that this problem also extends to a larger phylogeny of TBEV sequences. This work highlights a previously unknown caveat of tick-borne flavivirus evolutionary analysis which may be important for understanding the evolution of these important pathogens.

scholarly journals Genome-wide scans of selection highlight the impact sof biotic and abiotic constraints in natural populations of the model grass Brachypodium distachyon

2018 ◽  
Author(s):  
Yann Bourgeois ◽  
Christoph Stritt ◽  
Jean-Claude Walser ◽  
Sean P. Gordon ◽  
John P. Vogel ◽  
...  
Keyword(s):  
Candidate Genes ◽  
Population Genomics ◽  
Balancing Selection ◽  
Spatial Scales ◽  
Brachypodium Distachyon ◽  
Grass Species ◽  
Whole Genome Sequencing Data ◽  
Genome Wide ◽  
Genomic Regions ◽  
The Impact

SummaryGrasses are essential plants for ecosystem functioning. Quantifying the selective pressures that act on natural variation in grass species is therefore essential regarding biodiversity maintenance. In this study, we investigate the selection pressures that act on two distinct populations of the grass model Brachypodium distachyon without prior knowledge about the traits under selection. We took advantage of whole-genome sequencing data produced for 44 natural accessions of B. distachyon and used complementary genome-wide scans of selection (GWSS) methods to detect genomic regions under balancing and positive selection. We show that selection is shaping genetic diversity at multiple temporal and spatial scales in this species and affects different genomic regions across the two populations. Gene Ontology annotation of candidate genes reveals that pathogens may constitute important factors of positive and balancing selection in Brachypodium distachyon. We eventually cross-validated our results with QTL data available for leaf-rust resistance in this species and demonstrate that, when paired with classical trait mapping, GWSS can help pinpointing candidate genes for further molecular validation. Thanks to a near-base perfect reference genome and the large collection of freely available natural accessions collected across its natural range, B. distachyon appears as a prime system for studies in ecology, population genomics and evolutionary biology.

scholarly journals Genomic analyses suggest strong population connectivity over large spatial scales of the commercially important baitworm, Australonuphis teres (Onuphidae)

2020 ◽  
Vol 71 (11) ◽  
pp. 1549
Author(s):  
Amanda Padovan ◽  
Rowan C. Chick ◽  
Victoria J. Cole ◽  
Ludovic Dutoit ◽  
Patricia A. Hutchings ◽  
...  
Keyword(s):  
Gene Flow ◽  
Spatial Scales ◽  
Population Connectivity ◽  
Eastern Coast ◽  
Marine Biodiversity ◽  
Marine Animals ◽  
Long Distance ◽  
South Wales ◽  
Genome Wide ◽  
Eastern Australia

Barriers to dispersal can disrupt gene flow between populations, resulting in genetically distinct populations. Although many marine animals have potential for long-distance dispersal via a planktonic stage, gene flow among populations separated by large geographic distances is not always evident. Polychaetes are ecologically important and have been used as biological surrogates for marine biodiversity. Some polychaete species are used as bait for recreational fisheries, with this demand supporting commercial fisheries for polychaetes to service the retail bait market. However, despite their ecological and economic importance, very little is known about the life history or population dynamics of polychaetes, and few studies have used genetic or genomic approaches to understand polychaete population connectivity. Here, we investigate the population structure of one commonly collected beachworm species used for bait on the eastern coast of Australia, namely, Australonuphis teres, by using genome-wide single-nucleotide polymorphism data. We sampled A. teres from hierarchical nested spatial scales along 900km of the coast in New South Wales. We identified six genetic groups, but there was no clear geographic pattern of distribution. Our results suggest that there is considerable gene flow among the sampled populations. These high-resolution genomic data support the findings of previous studies, and we infer that oceanographic processes promote genetic exchange among polychaete populations in south-eastern Australia.

scholarly journals Whole-Genome Sequencing and Characterization of Buffalo Genetic Resources: Recent Advances and Future Challenges

Animals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 904
Author(s):  
Saif ur Rehman ◽  
Faiz-ul Hassan ◽  
Xier Luo ◽  
Zhipeng Li ◽  
Qingyou Liu
Keyword(s):  
Selective Breeding ◽  
Reference Genome ◽  
De Novo ◽  
Phenotypic Diversity ◽  
Molecular Data ◽  
Genomic Diversity ◽  
Production Performance ◽  
Phylogeographic Structure ◽  
Economic Significance ◽  
And Performance

The buffalo was domesticated around 3000–6000 years ago and has substantial economic significance as a meat, dairy, and draught animal. The buffalo has remained underutilized in terms of the development of a well-annotated and assembled reference genome de novo. It is mandatory to explore the genetic architecture of a species to understand the biology that helps to manage its genetic variability, which is ultimately used for selective breeding and genomic selection. Morphological and molecular data have revealed that the swamp buffalo population has strong geographical genomic diversity with low gene flow but strong phenotypic consistency, while the river buffalo population has higher phenotypic diversity with a weak phylogeographic structure. The availability of recent high-quality reference genome and genotyping marker panels has invigorated many genome-based studies on evolutionary history, genetic diversity, functional elements, and performance traits. The increasing molecular knowledge syndicate with selective breeding should pave the way for genetic improvement in the climatic resilience, disease resistance, and production performance of water buffalo populations globally.

scholarly journals Genomic variation in the American pika: signatures of geographic isolation and implications for conservation

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Kelly B. Klingler ◽  
Joshua P. Jahner ◽  
Thomas L. Parchman ◽  
Chris Ray ◽  
Mary M. Peacock
Keyword(s):  
Genetic Variation ◽  
Genetic Structure ◽  
Sierra Nevada ◽  
Spatial Genetic Structure ◽  
Spatial Scales ◽  
Thermal Sensitivity ◽  
Genomic Variation ◽  
Genome Wide ◽  
A Genome ◽  
American Pika

Abstract Background Distributional responses by alpine taxa to repeated, glacial-interglacial cycles throughout the last two million years have significantly influenced the spatial genetic structure of populations. These effects have been exacerbated for the American pika (Ochotona princeps), a small alpine lagomorph constrained by thermal sensitivity and a limited dispersal capacity. As a species of conservation concern, long-term lack of gene flow has important consequences for landscape genetic structure and levels of diversity within populations. Here, we use reduced representation sequencing (ddRADseq) to provide a genome-wide perspective on patterns of genetic variation across pika populations representing distinct subspecies. To investigate how landscape and environmental features shape genetic variation, we collected genetic samples from distinct geographic regions as well as across finer spatial scales in two geographically proximate mountain ranges of eastern Nevada. Results Our genome-wide analyses corroborate range-wide, mitochondrial subspecific designations and reveal pronounced fine-scale population structure between the Ruby Mountains and East Humboldt Range of eastern Nevada. Populations in Nevada were characterized by low genetic diversity (π = 0.0006–0.0009; θW = 0.0005–0.0007) relative to populations in California (π = 0.0014–0.0019; θW = 0.0011–0.0017) and the Rocky Mountains (π = 0.0025–0.0027; θW = 0.0021–0.0024), indicating substantial genetic drift in these isolated populations. Tajima’s D was positive for all sites (D = 0.240–0.811), consistent with recent contraction in population sizes range-wide. Conclusions Substantial influences of geography, elevation and climate variables on genetic differentiation were also detected and may interact with the regional effects of anthropogenic climate change to force the loss of unique genetic lineages through continued population extirpations in the Great Basin and Sierra Nevada.

scholarly journals Population genomics and antimicrobial resistance dynamics of Escherichia coli in wastewater and river environments

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jose F. Delgado-Blas ◽  
Cristina M. Ovejero ◽  
Sophia David ◽  
Natalia Montero ◽  
William Calero-Caceres ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Population Genomics ◽  
Population Diversity ◽  
Genomic Diversity ◽  
Resistant Bacteria ◽  
Aquatic Environments ◽  
E Coli ◽  
Water Ecosystems ◽  
Sequence Types

AbstractAquatic environments are key niches for the emergence, evolution and dissemination of antimicrobial resistance. However, the population diversity and the genetic elements that drive the dynamics of resistant bacteria in different aquatic environments are still largely unknown. The aim of this study was to understand the population genomics and evolutionary events of Escherichia coli resistant to clinically important antibiotics including aminoglycosides, in anthropogenic and natural water ecosystems. Here we show that less different E. coli sequence types (STs) are identified in wastewater than in rivers, albeit more resistant to antibiotics, and with significantly more plasmids/cell (6.36 vs 3.72). However, the genomic diversity within E. coli STs in both aquatic environments is similar. Wastewater environments favor the selection of conserved chromosomal structures associated with diverse flexible plasmids, unraveling promiscuous interplasmidic resistance genes flux. On the contrary, the key driver for river E. coli adaptation is a mutable chromosome along with few plasmid types shared between diverse STs harboring a limited resistance gene content.

scholarly journals Comparing the utility of in vivo transposon mutagenesis approaches in yeast species to infer gene essentiality

2019 ◽  
Author(s):  
Anton Levitan ◽  
Andrew N. Gale ◽  
Emma K. Dallon ◽  
Darby W. Kozan ◽  
Kyle W. Cunningham ◽  
...  
Keyword(s):  
Machine Learning ◽  
Large Scale ◽  
Yeast Species ◽  
Transposon Mutagenesis ◽  
Learning Approach ◽  
Long Distance ◽  
Gene Essentiality ◽  
Genome Wide ◽  
Machine Learning Approach

ABSTRACTIn vivo transposon mutagenesis, coupled with deep sequencing, enables large-scale genome-wide mutant screens for genes essential in different growth conditions. We analyzed six large-scale studies performed on haploid strains of three yeast species (Saccharomyces cerevisiae, Schizosaccaromyces pombe, and Candida albicans), each mutagenized with two of three different heterologous transposons (AcDs, Hermes, and PiggyBac). Using a machine-learning approach, we evaluated the ability of the data to predict gene essentiality. Important data features included sufficient numbers and distribution of independent insertion events. All transposons showed some bias in insertion site preference because of jackpot events, and preferences for specific insertion sequences and short-distance vs long-distance insertions. For PiggyBac, a stringent target sequence limited the ability to predict essentiality in genes with few or no target sequences. The machine learning approach also robustly predicted gene function in less well-studied species by leveraging cross-species orthologs. Finally, comparisons of isogenic diploid versus haploid S. cerevisiae isolates identified several genes that are haplo-insufficient, while most essential genes, as expected, were recessive. We provide recommendations for the choice of transposons and the inference of gene essentiality in genome-wide studies of eukaryotic haploid microbes such as yeasts, including species that have been less amenable to classical genetic studies.

scholarly journals Spatial population genomics of a recent mosquito invasion

2020 ◽  
Author(s):  
Thomas L Schmidt ◽  
T. Swan ◽  
Jessica Chung ◽  
Stephan Karl ◽  
Samuel Demok ◽  
...  
Keyword(s):  
Gene Flow ◽  
Population Genomics ◽  
Isolation By Distance ◽  
Spatial Genetic Structure ◽  
Nucleotide Polymorphisms ◽  
Discrete Events ◽  
Long Distance ◽  
Population Genomic ◽  
Asian Tiger ◽  
Study Designs

AbstractPopulation genomic approaches can characterise dispersal across a single generation through to many generations in the past, bridging the gap between individual movement and intergenerational gene flow. These approaches are particularly useful when investigating dispersal in recently altered systems, where they provide a way of inferring long-distance dispersal between newly established populations and their interactions with existing populations. Human-mediated biological invasions represent such altered systems which can be investigated with appropriate study designs and analyses. Here we apply temporally-restricted sampling and a range of population genomic approaches to investigate dispersal in a 2004 invasion of Aedes albopictus (the Asian tiger mosquito) in the Torres Strait Islands (TSI) of Australia. We sampled mosquitoes from 13 TSI villages simultaneously and genotyped 373 mosquitoes at genome-wide single nucleotide polymorphisms (SNPs): 331 from the TSI, 36 from Papua New Guinea (PNG), and 4 incursive mosquitoes detected in uninvaded regions. Within villages, spatial genetic structure varied substantially but overall displayed isolation by distance and a neighbourhood size of 232–577. Close kin dyads revealed recent movement between islands 31–203 km apart, and deep learning inferences showed incursive Ae. albopictus had travelled to uninvaded regions from both adjacent and non-adjacent islands. Private alleles and a coancestry matrix indicated direct gene flow from PNG into nearby islands. Outlier analyses also detected four linked alleles introgressed from PNG, with the alleles surrounding 12 resistance-associated cytochrome P450 genes. By treating dispersal as both an intergenerational process and a set of discrete events, we describe a highly interconnected invasive system.

scholarly journals Genome-wide characterization of genetic diversity and population structure of Valeriana officinalis L.

2019 ◽  
Author(s):  
Maja Boczkowska ◽  
Katarzyna Bączek ◽  
Olga Kosakowska ◽  
Anna Rucińska ◽  
Wiesław Podyma ◽  
...  
Keyword(s):  
Population Structure ◽  
Population Genomics ◽  
Natural Populations ◽  
Valeriana Officinalis ◽  
Wild Populations ◽  
Genetic Fingerprint ◽  
Genome Wide ◽  
Species Population ◽  
Outcrossing Species

Abstract Background: Valeriana officinalis L. is one of the most important medicinal plant with a mild sedative, nervine, antispasmodic and relaxant effect. Despite a substantial number of studies on this species, population genomics has not yet been analyzed. The main aim of this study was: characterization of genetic variation of natural populations of V. officinalis in Poland and comparison of variation of wild populations and the cultivated form using Next Generation Sequencing based DArTseq technique. We also would like to establish foundations for genetic monitoring of the species in the future and to develop genetic fingerprint profile for samples deposited in gene bank and in natural sites in order to assess the degree of their genetic integrity and population structure preservation in the future.Results: The major and also the most astounding result of our work is the low level of observed heterozygosity of individual plants from natural populations despite the fact that the species is widespread in the studied area. Inbreeding, in naturally outcrossing species such as valerian, decreases the reproductive success. The analysis of the population structure indicated the potential presence of metapopulation in a broad area of Poland and the formation of a distinct gene pool in Bieszczady Mountains. The results also indicate the presence of individuals of the cultivated form in natural populations in the region where the species is cultivated for the needs of the pharmaceutical industry and this could lead to structural and genetic imbalance in wild populations.Conclusions: The DArTseq technology can be applied effectively in genetic studies of V. officinalis. The genetic variability of wild populations is in fact significantly lower than assumed. Individuals from the cultivated population are found in the natural environment and their impact on wild populations should be monitored.

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