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September 22, 2019

Genome evolution across 1,011 Saccharomyces cerevisiae isolates.

Large-scale population genomic surveys are essential to explore the phenotypic diversity of natural populations. Here we report the whole-genome sequencing and phenotyping of 1,011 Saccharomyces cerevisiae isolates, which together provide an accurate evolutionary picture of the genomic variants that shape the species-wide phenotypic landscape of this yeast. Genomic analyses support a single ‘out-of-China’ origin for this species, followed by several independent domestication events. Although domesticated isolates exhibit high variation in ploidy, aneuploidy and genome content, genome evolution in wild isolates is mainly driven by the accumulation of single nucleotide polymorphisms. A common feature is the extensive loss of heterozygosity, which represents an essential source of inter-individual variation in this mainly asexual species. Most of the single nucleotide polymorphisms, including experimentally identified functional polymorphisms, are present at very low frequencies. The largest numbers of variants identified by genome-wide association are copy-number changes, which have a greater phenotypic effect than do single nucleotide polymorphisms. This resource will guide future population genomics and genotype-phenotype studies in this classic model system.

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September 22, 2019

RTS,S/AS01 malaria vaccine mismatch observed among Plasmodium falciparum isolates from southern and central Africa and globally.

The RTS,S/AS01 malaria vaccine encompasses the central repeats and C-terminal of Plasmodium falciparum circumsporozoite protein (PfCSP). Although no Phase II clinical trial studies observed evidence of strain-specific immunity, recent studies show a decrease in vaccine efficacy against non-vaccine strain parasites. In light of goals to reduce malaria morbidity, anticipating the effectiveness of RTS,S/AS01 is critical to planning widespread vaccine introduction. We deep sequenced C-terminal Pfcsp from 77 individuals living along the international border in Luapula Province, Zambia and Haut-Katanga Province, the Democratic Republic of the Congo (DRC) and compared translated amino acid haplotypes to the 3D7 vaccine strain. Only 5.2% of the 193 PfCSP sequences from the Zambia-DRC border region matched 3D7 at all 84 amino acids. To further contextualize the genetic diversity sampled in this study with global PfCSP diversity, we analyzed an additional 3,809 Pfcsp sequences from the Pf3k database and constructed a haplotype network representing 15 countries from Africa and Asia. The diversity observed in our samples was similar to the diversity observed in the global haplotype network. These observations underscore the need for additional research assessing genetic diversity in P. falciparum and the impact of PfCSP diversity on RTS,S/AS01 efficacy.

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September 22, 2019

Genomic analysis of a pan-resistant isolate of Klebsiella pneumoniae, United States 2016.

Antimicrobial resistance is a threat to public health globally and leads to an estimated 23,000 deaths annually in the United States alone. Here, we report the genomic characterization of an unusualKlebsiella pneumoniae, nonsusceptible to all 26 antibiotics tested, that was isolated from a U.S.The isolate harbored four known beta-lactamase genes, including plasmid-mediatedblaNDM-1andblaCMY-6, as well as chromosomalblaCTX-M-15andblaSHV-28, which accounted for resistance to all beta-lactams tested. In addition, sequence analysis identified mechanisms that could explain all other reported nonsusceptibility results, including nonsusceptibility to colistin, tigecycline, and chloramphenicol. Two plasmids, IncA/C2 and IncFIB, were closely related to mobile elements described previously and isolated from Gram-negative bacteria from China, Nepal, India, the United States, and Kenya, suggesting possible origins of the isolate and plasmids. This is one of the firstK. pneumoniaeisolates in the United States to have been reported to the Centers for Disease Control and Prevention (CDC) as nonsusceptible to all drugs tested, including all beta-lactams, colistin, and tigecycline. IMPORTANCE Antimicrobial resistance is a major public health threat worldwide. Bacteria that are nonsusceptible or resistant to all antimicrobials available are of major concern to patients and the public because of lack of treatment options and potential for spread. AKlebsiella pneumoniaestrain that was nonsusceptible to all tested antibiotics was isolated from a U.S.Mechanisms that could explain all observed phenotypic antimicrobial resistance phenotypes, including resistance to colistin and beta-lactams, were identified through whole-genome sequencing. The large variety of resistance determinants identified demonstrates the usefulness of whole-genome sequencing for detecting these genes in an outbreak response. Sequencing of isolates with rare and unusual phenotypes can provide information on how these extremely resistant isolates develop, including whether resistance is acquired on mobile elements or accumulated through chromosomal mutations. Moreover, this provides further insight into not only detecting these highly resistant organisms but also preventing their spread.

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September 22, 2019

Chinook salmon (Oncorhynchus tshawytscha) genome and transcriptome.

When unifying genomic resources among studies and comparing data between species, there is often no better resource than a genome sequence. Having a reference genome for the Chinook salmon (Oncorhynchus tshawytscha) will enable the extensive genomic resources available for Pacific salmon, Atlantic salmon, and rainbow trout to be leveraged when asking questions related to the Chinook salmon. The Chinook salmon’s wide distribution, long cultural impact, evolutionary history, substantial hatchery production, and recent wild-population decline make it an important research species. In this study, we sequenced and assembled the genome of a Chilliwack River Hatchery female Chinook salmon (gynogenetic and homozygous at all loci). With a reference genome sequence, new questions can be asked about the nature of this species, and its role in a rapidly changing world.

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September 22, 2019

The complete chloroplast genome of Chrysanthemum boreale (Asteraceae)

Chrysanthemum boreale is a perennial plant in the Asteraceae family that is native to eastern Asia and has both ornamental and herbal uses. Here, we determined the complete chloroplast genome sequence for C. boreale using long-read sequencing. The chloroplast genome was 151,012?bp and consisted of a large single copy (LSC) region (82,817?bp), a small single copy (SSC) region (18,281?bp) and two inverted repeats (IRs) (24,957?bp). It was predicted to contain 131 genes, including 87 protein-coding genes, eight rRNAs and 46 tRNAs. Phylogenetic analysis of chloroplast genomes clustered C. boreale with other Chrysanthemum and Asteraceae species.

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September 22, 2019

Draft genome sequence of Camellia sinensis var. sinensis provides insights into the evolution of the tea genome and tea quality.

Tea, one of the world’s most important beverage crops, provides numerous secondary metabolites that account for its rich taste and health benefits. Here we present a high-quality sequence of the genome of tea, Camellia sinensis var. sinensis (CSS), using both Illumina and PacBio sequencing technologies. At least 64% of the 3.1-Gb genome assembly consists of repetitive sequences, and the rest yields 33,932 high-confidence predictions of encoded proteins. Divergence between two major lineages, CSS and Camellia sinensis var. assamica (CSA), is calculated to ~0.38 to 1.54 million years ago (Mya). Analysis of genic collinearity reveals that the tea genome is the product of two rounds of whole-genome duplications (WGDs) that occurred ~30 to 40 and ~90 to 100 Mya. We provide evidence that these WGD events, and subsequent paralogous duplications, had major impacts on the copy numbers of secondary metabolite genes, particularly genes critical to producing three key quality compounds: catechins, theanine, and caffeine. Analyses of transcriptome and phytochemistry data show that amplification and transcriptional divergence of genes encoding a large acyltransferase family and leucoanthocyanidin reductases are associated with the characteristic young leaf accumulation of monomeric galloylated catechins in tea, while functional divergence of a single member of the glutamine synthetase gene family yielded theanine synthetase. This genome sequence will facilitate understanding of tea genome evolution and tea metabolite pathways, and will promote germplasm utilization for breeding improved tea varieties. Copyright © 2018 the Author(s). Published by PNAS.

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September 22, 2019

Comparative genomics of cocci-shaped Sporosarcina strains with diverse spatial isolation.

Cocci-shaped Sporosarcina strains are currently one of the few known cocci-shaped spore-forming bacteria, yet we know very little about the genomics. The goal of this study is to utilize comparative genomics to investigate the diversity of cocci-shaped Sporosarcina strains that differ in their geographical isolation and show different nutritional requirements.For this study, we sequenced 28 genomes of cocci-shaped Sporosarcina strains isolated from 13 different locations around the world. We generated the first six complete genomes and methylomes utilizing PacBio sequencing, and an additional 22 draft genomes using Illumina sequencing. Genomic analysis revealed that cocci-shaped Sporosarcina strains contained an average genome of 3.3 Mb comprised of 3222 CDS, 54 tRNAs and 6 rRNAs, while only two strains contained plasmids. The cocci-shaped Sporosarcina genome on average contained 2.3 prophages and 15.6 IS elements, while methylome analysis supported the diversity of these strains as only one of 31 methylation motifs were shared under identical growth conditions. Analysis with a 90% identity cut-off revealed 221 core genes or ~?7% of the genome, while a 30% identity cut-off generated a pan-genome of 8610 genes. The phylogenetic relationship of the cocci-shaped Sporosarcina strains based on either core genes, accessory genes or spore-related genes consistently resulted in the 29 strains being divided into eight clades.This study begins to unravel the phylogenetic relationship of cocci-shaped Sporosarcina strains, and the comparative genomics of these strains supports identification of several new species.

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September 22, 2019

De novo genome assembly of the red silk cotton tree (Bombax ceiba).

Bombax ceiba L. (the red silk cotton tree) is a large deciduous tree that is distributed in tropical and sub-tropical Asia as well as northern Australia. It has great economic and ecological importance, with several applications in industry and traditional medicine in many Asian countries. To facilitate further utilization of this plant resource, we present here the draft genome sequence for B. ceiba.We assembled a relatively intact genome of B. ceiba by using PacBio single-molecule sequencing and BioNano optical mapping technologies. The final draft genome is approximately 895 Mb long, with contig and scaffold N50 sizes of 1.0 Mb and 2.06 Mb, respectively.The high-quality draft genome assembly of B. ceiba will be a valuable resource enabling further genetic improvement and more effective use of this tree species.

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September 22, 2019

Genomic characterization of nonclonal mcr-1-positive multidrug-resistant Klebsiella pneumoniae from clinical samples in Thailand.

Multidrug-resistant Klebsiella pneumoniae strains are one of the most prevalent causes of nosocomial infections and pose an increasingly dangerous public health threat. The lack of remaining treatment options has resulted in the utilization of older drug classes, including colistin. As a drug of last resort, the discovery of plasmid-mediated colistin resistance by mcr-1 denotes the potential development of pandrug-resistant bacterial pathogens. To address the emergence of the mcr-1 gene, 118 gram-negative Enterobacteriaceae isolated from clinical samples collected at Queen Sirikit Naval Hospital in Chonburi, Thailand were screened for colistin resistance using automated antimicrobial susceptibility testing and conventional PCR screening. Two K. pneumoniae strains, QS17-0029 and QS17-0161, were positive for mcr-1, and both isolates were sequenced to closure using short- and long-read whole-genome sequencing. QS17-0029 carried 16 antibiotic resistance genes in addition to mcr-1, including 2 carbapenemases, blaNDM-1 and blaOXA-232. QS17-0161 carried 13 antibiotic resistance genes in addition to mcr-1, including the extended-spectrum ß-lactamase blaCTX-M-55. Both isolates carried multiple plasmids, but mcr-1 was located alone on highly similar 33.9?Kb IncX4 plasmids in both isolates. The IncX4 plasmid shared considerable homology to other mcr-1-containing IncX4 plasmids. This is the first report of a clinical K. pneumoniae strain from Thailand carrying mcr-1 as well as the first strain to simultaneously carry mcr-1 and multiple carbapenemase genes (QS17-0029). The identification and characterization of these isolates serves to highlight the urgent need for continued surveillance and intervention in Southeast Asia, where extensively drug-resistant pathogens are being increasingly identified in hospital-associated infections.

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September 22, 2019

A whole genome assembly of the horn fly, Haematobia irritans, and prediction of genes with roles in metabolism and sex determination.

Haematobia irritans, commonly known as the horn fly, is a globally distributed blood-feeding pest of cattle that is responsible for significant economic losses to cattle producers. Chemical insecticides are the primary means for controlling this pest but problems with insecticide resistance have become common in the horn fly. To provide a foundation for identification of genomic loci for insecticide resistance and for discovery of new control technology, we report the sequencing, assembly, and annotation of the horn fly genome. The assembled genome is 1.14 Gb, comprising 76,616 scaffolds with N50 scaffold length of 23 Kb. Using RNA-Seq data, we have predicted 34,413 gene models of which 19,185 have been assigned functional annotations. Comparative genomics analysis with the Dipteran flies Musca domestica L., Drosophila melanogaster, and Lucilia cuprina, show that the horn fly is most closely related to M. domestica, sharing 8,748 orthologous clusters followed by D. melanogaster and L. cuprina, sharing 7,582 and 7,490 orthologous clusters respectively. We also identified a gene locus for the sodium channel protein in which mutations have been previously reported that confers target site resistance to the most common class of pesticides used in fly control. Additionally, we identified 276 genomic loci encoding members of metabolic enzyme gene families such as cytochrome P450s, esterases and glutathione S-transferases, and several genes orthologous to sex determination pathway genes in other Dipteran species. Copyright © 2018 Konganti et al.

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September 22, 2019

Size and content of the sex-determining region of the Y chromosome in dioecious Mercurialis annua, a plant with homomorphic sex chromosomes.

Dioecious plants vary in whether their sex chromosomes are heteromorphic or homomorphic, but even homomorphic sex chromosomes may show divergence between homologues in the non-recombining, sex-determining region (SDR). Very little is known about the SDR of these species, which might represent particularly early stages of sex-chromosome evolution. Here, we assess the size and content of the SDR of the diploid dioecious herb Mercurialis annua, a species with homomorphic sex chromosomes and mild Y-chromosome degeneration. We used RNA sequencing (RNAseq) to identify new Y-linked markers for M. annua. Twelve of 24 transcripts showing male-specific expression in a previous experiment could be amplified by polymerase chain reaction (PCR) only from males, and are thus likely to be Y-linked. Analysis of genome-capture data from multiple populations of M. annua pointed to an additional six male-limited (and thus Y-linked) sequences. We used these markers to identify and sequence 17 sex-linked bacterial artificial chromosomes (BACs), which form 11 groups of non-overlapping sequences, covering a total sequence length of about 1.5 Mb. Content analysis of this region suggests that it is enriched for repeats, has low gene density, and contains few candidate sex-determining genes. The BACs map to a subset of the sex-linked region of the genetic map, which we estimate to be at least 14.5 Mb. This is substantially larger than estimates for other dioecious plants with homomorphic sex chromosomes, both in absolute terms and relative to their genome sizes. Our data provide a rare, high-resolution view of the homomorphic Y chromosome of a dioecious plant.

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September 22, 2019

Acquisition of resistance to carbapenem and macrolide-mediated quorum sensing inhibition by Pseudomonas aeruginosa via ICE Tn4371 6385

Pseudomonas aeruginosa can cause life-threatening infections in immunocompromised patients. The first-line agents to treat P. aeruginosa infections are carbapenems. However, the emergence of carbapenem-resistant P. aeruginosa strains greatly compromised the effec- tiveness of carbapenem treatment, which makes the surveillance on their spreading and transmission important. Here we characterized the full-length genomes of two carbapenem- resistant P. aeruginosa clinical isolates that are capable of producing New Delhi metallo-ß- lactamase-1 (NDM-1). We show that blaNDM-1 is carried by a novel integrative and conjugative element (ICE) ICETn43716385, which also carries the macrolide resistance gene msr(E) and the florfenicol resistance gene floR. By exogenously expressing msr(E) in P. aeruginosa laboratory strains, we show that Msr(E) can abolish azithromycin-mediated quorum sensing inhibition in vitro and anti-Pseudomonas effect in vivo. We conclude that ICEs are important in transmitting carbapenem resistance, and that anti-virulence treatment of P. aeruginosa infections using sub-inhibitory concentrations of macrolides can be challenged by horizontal gene transfer.

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September 22, 2019

The presence of colistin resistance gene mcr-1 and -3 in ESBL producing Escherichia coli isolated from food in Ho Chi Minh City, Vietnam.

Colistin is indicated for the treatment of multidrug-resistant gram-negative bacterial infections. However, the spread of colistin-resistant bacteria harbouring an mcr gene has become a serious concern. This study investigated local foods in Vietnam for contamination with colistin-resistant bacteria. A total of 261 extended-spectrum ß-lactamase (ESBL)- and AmpC-producing Escherichia coli isolates from 330 meat and seafood products were analysed for colistin susceptibility and the presence of mcr genes. Approximately, 24% (62/261) of ESBL- or AmpC-producing E. coli isolates showed colistin resistance; 97% (60/62) of colistin-resistant isolates harboured mcr-1, whereas 3% (2/62) harboured mcr-3. As the result of plasmid analysis of two strains, both plasmids harbouring mcr-3 revealed that plasmid replicon type was IncFII. Sequencing analysis indicated that an insertion sequence was present near mcr-3, suggesting that IncFII plasmids harbouring mcr-3 could be transferred to other bacterial species by horizontal transfer of the plasmid or transfer with some insertion sequence. In conclusion, ESBL-producing E. coli and AmpC-producing E. coli have acquired colistin resistance because 24% of such isolates show colistin resistance and 3% of the colistin-resistant strains harbour mcr-3. We reported the present of the mcr-3-carrying ESBL-producing E. coli isolated from pork in Vietnam.

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September 22, 2019

Genetic diversity of Cryptosporidium hominis in a Bangladeshi community as revealed by whole genome sequencing.

We studied the genetic diversity of Cryptosporidium hominis infections in slum-dwelling infants from Dhaka over a 2-year period. Cryptosporidium hominis infections were common during the monsoon, and were genetically diverse as measured by gp60 genotyping and whole-genome resequencing. Recombination in the parasite was evidenced by the decay of linkage disequilibrium in the genome over <300 bp. Regions of the genome with high levels of polymorphism were also identified. Yet to be determined is if genomic diversity is responsible in part for the high rate of reinfection, seasonality, and varied clinical presentations of cryptosporidiosis in this population.

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September 22, 2019

Mycobacterial biomaterials and resources for researchers.

There are many resources available to mycobacterial researchers, including culture collections around the world that distribute biomaterials to the general scientific community, genomic and clinical databases, and powerful bioinformatics tools. However, many of these resources may be unknown to the research community. This review article aims to summarize and publicize many of these resources, thus strengthening the quality and reproducibility of mycobacterial research by providing the scientific community access to authenticated and quality-controlled biomaterials and a wealth of information, analytical tools and research opportunities.

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