Menu
September 22, 2019  |  

Whole genome and transcriptome maps of the entirely black native Korean chicken breed Yeonsan Ogye.

Yeonsan Ogye (YO), an indigenous Korean chicken breed (Gallus gallus domesticus), has entirely black external features and internal organs. In this study, the draft genome of YO was assembled using a hybrid de novo assembly method that takes advantage of high-depth Illumina short reads (376.6X) and low-depth Pacific Biosciences (PacBio) long reads (9.7X).The contig and scaffold NG50s of the hybrid de novo assembly were 362.3 Kbp and 16.8 Mbp, respectively. The completeness (97.6%) of the draft genome (Ogye_1.1) was evaluated with single-copy orthologous genes using Benchmarking Universal Single-Copy Orthologs and found to be comparable to the current chicken reference genome (galGal5; 97.4%; contigs were assembled with high-depth PacBio long reads (50X) and scaffolded with short reads) and superior to other avian genomes (92%-93%; assembled with short read-only or hybrid methods). Compared to galGal4 and galGal5, the draft genome included 551 structural variations including the fibromelanosis (FM) locus duplication, related to hyperpigmentation. To comprehensively reconstruct transcriptome maps, RNA sequencing and reduced representation bisulfite sequencing data were analyzed from 20 tissues, including 4 black tissues (skin, shank, comb, and fascia). The maps included 15,766 protein-coding and 6,900 long noncoding RNA genes, many of which were tissue-specifically expressed and displayed tissue-specific DNA methylation patterns in the promoter regions.We expect that the resulting genome sequence and transcriptome maps will be valuable resources for studying domestic chicken breeds, including black-skinned chickens, as well as for understanding genomic differences between breeds and the evolution of hyperpigmented chickens and functional elements related to hyperpigmentation.


September 22, 2019  |  

Heterogeneous and flexible transmission of mcr-1 in hospital-associated Escherichia coli.

The recent emergence of a transferable colistin resistance mechanism, MCR-1, has gained global attention because of its threat to clinical treatment of infections caused by multidrug-resistant Gram-negative bacteria. However, the possible transmission route of mcr-1 among Enterobacteriaceae species in clinical settings is largely unknown. Here, we present a comprehensive genomic analysis of Escherichia coli isolates collected in a hospital in Hangzhou, China. We found that mcr-1-carrying isolates from clinical infections and feces of inpatients and healthy volunteers were genetically diverse and were not closely related phylogenetically, suggesting that clonal expansion is not involved in the spread of mcr-1 The mcr-1 gene was found on either chromosomes or plasmids, but in most of the E. coli isolates, mcr-1 was carried on plasmids. The genetic context of the plasmids showed considerable diversity as evidenced by the different functional insertion sequence (IS) elements, toxin-antitoxin (TA) systems, heavy metal resistance determinants, and Rep proteins of broad-host-range plasmids. Additionally, the genomic analysis revealed nosocomial transmission of mcr-1 and the coexistence of mcr-1 with other genes encoding ß-lactamases and fluoroquinolone resistance in the E. coli isolates. These findings indicate that mcr-1 is heterogeneously disseminated in both commensal and pathogenic strains of E. coli, suggest the high flexibility of this gene in its association with diverse genetic backgrounds of the hosts, and provide new insights into the genome epidemiology of mcr-1 among hospital-associated E. coli strains. IMPORTANCE Colistin represents one of the very few available drugs for treating infections caused by extensively multidrug-resistant Gram-negative bacteria. The recently emergent mcr-1 colistin resistance gene threatens the clinical utility of colistin and has gained global attention. How mcr-1 spreads in hospital settings remains unknown and was investigated by whole-genome sequencing of mcr-1-carrying Escherichia coli in this study. The findings revealed extraordinary flexibility of mcr-1 in its spread among genetically diverse E. coli hosts and plasmids, nosocomial transmission of mcr-1-carrying E. coli, and the continuous emergence of novel Inc types of plasmids carrying mcr-1 and new mcr-1 variants. Additionally, mcr-1 was found to be frequently associated with other genes encoding ß-lactams and fluoroquinolone resistance. These findings provide important information on the transmission and epidemiology of mcr-1 and are of significant public health importance as the information is expected to facilitate the control of this significant antibiotic resistance threat. Copyright © 2018 Shen et al.


September 22, 2019  |  

Horizontal transfer of BovB and L1 retrotransposons in eukaryotes.

Transposable elements (TEs) are mobile DNA sequences, colloquially known as jumping genes because of their ability to replicate to new genomic locations. TEs can jump between organisms or species when given a vector of transfer, such as a tick or virus, in a process known as horizontal transfer. Here, we propose that LINE-1 (L1) and Bovine-B (BovB), the two most abundant TE families in mammals, were initially introduced as foreign DNA via ancient horizontal transfer events.Using analyses of 759 plant, fungal and animal genomes, we identify multiple possible L1 horizontal transfer events in eukaryotic species, primarily involving Tx-like L1s in marine eukaryotes. We also extend the BovB paradigm by increasing the number of estimated transfer events compared to previous studies, finding new parasite vectors of transfer such as bed bug, leech and locust, and BovB occurrences in new lineages such as bat and frog. Given that these transposable elements have colonised more than half of the genome sequence in today’s mammals, our results support a role for horizontal transfer in causing long-term genomic change in new host organisms.We describe extensive horizontal transfer of BovB retrotransposons and provide the first evidence that L1 elements can also undergo horizontal transfer. With the advancement of genome sequencing technologies and bioinformatics tools, we anticipate our study to be a valuable resource for inferring horizontal transfer from large-scale genomic data.


September 22, 2019  |  

The Chara genome: Secondary complexity and implications for plant terrestrialization.

Land plants evolved from charophytic algae, among which Charophyceae possess the most complex body plans. We present the genome of Chara braunii; comparison of the genome to those of land plants identified evolutionary novelties for plant terrestrialization and land plant heritage genes. C. braunii employs unique xylan synthases for cell wall biosynthesis, a phragmoplast (cell separation) mechanism similar to that of land plants, and many phytohormones. C. braunii plastids are controlled via land-plant-like retrograde signaling, and transcriptional regulation is more elaborate than in other algae. The morphological complexity of this organism may result from expanded gene families, with three cases of particular note: genes effecting tolerance to reactive oxygen species (ROS), LysM receptor-like kinases, and transcription factors (TFs). Transcriptomic analysis of sexual reproductive structures reveals intricate control by TFs, activity of the ROS gene network, and the ancestral use of plant-like storage and stress protection proteins in the zygote. Copyright © 2018 Elsevier Inc. All rights reserved.


September 22, 2019  |  

Phenotypic and genomic properties of Brachybacterium vulturis sp. nov. and Brachybacterium avium sp. nov.

Two strains, VM2412T and VR2415T, were isolated from the feces of an Andean condor (Vultur gryphus) living in Seoul Grand Park, Gyeonggi-do, South Korea. Cells of both strains were observed to be Gram-stain positive, non-motile, aerobic, catalase positive and oxidase negative. Growth was found to occur at 10-30°C, showing optimum growth at 30°C. The strains could tolerate up to 15% (w/v) NaCl concentration and grow at pH 6-9. The strains shared 99.3% 16S rRNA gene sequence similarity to each other but were identified as two distinct species based on 89.0-89.2% ANIb, 90.3% ANIm, 89.7% OrthoANI and 38.0% dDDH values calculated using whole genome sequences. Among species with validly published names, Brachybacterium ginsengisoli DCY80T shared high 16S rRNA gene sequence similarities with strains VM2412T (98.7%) and VR2415T (98.4%) and close genetic relatedness with strains VM2412T (83.3-83.5% ANIb, 87.0% ANIm, 84.3% OrthoANI and 27.8% dDDH) and VR2415T (82.8-83.2% ANIb, 86.7% ANIm, 83.9% OrthoANI and 27.2% dDDH). The major fatty acid of the two strains was identified as anteiso-C15:0 and the polar lipids consisted of phosphatidylglycerol, diphosphatidylglycerol, presumptively phosphatidylethanolamine and three unidentified glycolipids. Strain VR2415T also produced an unidentified phospholipid. The cell walls of the two strains contained meso-diaminopimelic acid as diagnostic diamino acid and the whole cell sugars were ribose, glucose, and galactose. The strains contained MK-7 as their predominant menaquinone. The genomes of strains VM2412T, VR2415T, and B. ginsengisoli DCY80T were sequenced in this study. The genomic G+C contents of strains VM2412T and VR2415T were determined to be 70.8 and 70.4 mol%, respectively. A genome-based phylogenetic tree constructed using an up-to-date bacterial core gene set (UBCG) showed that the strains formed a clade with members of the genus Brachybacterium, supporting their taxonomic classification into the genus Brachybacterium. Based on phenotypic and genotypic analyses in this study, strains VM2412T and VR2415T are considered to represent two novel species of the genus Brachybacterium and the names Brachybacterium vulturis sp. nov. and Brachybacterium avium sp. nov. are proposed for strains VM2412T (=KCTC 39996T = JCM 32142T) and VR2415T (=KCTC 39997T = JCM 32143T), respectively.


September 22, 2019  |  

Discovery of new genes involved in curli production by a uropathogenic Escherichia coli strain from the highly virulent O45:K1:H7 lineage.

Curli are bacterial surface-associated amyloid fibers that bind to the dye Congo red (CR) and facilitate uropathogenic Escherichia coli (UPEC) biofilm formation and protection against host innate defenses. Here we sequenced the genome of the curli-producing UPEC pyelonephritis strain MS7163 and showed it belongs to the highly virulent O45:K1:H7 neonatal meningitis-associated clone. MS7163 produced curli at human physiological temperature, and this correlated with biofilm growth, resistance of sessile cells to the human cationic peptide cathelicidin, and enhanced colonization of the mouse bladder. We devised a forward genetic screen using CR staining as a proxy for curli production and identified 41 genes that were required for optimal CR binding, of which 19 genes were essential for curli synthesis. Ten of these genes were novel or poorly characterized with respect to curli synthesis and included genes involved in purine de novo biosynthesis, a regulator that controls the Rcs phosphorelay system, and a novel repressor of curli production (referred to as rcpA). The involvement of these genes in curli production was confirmed by the construction of defined mutants and their complementation. The mutants did not express the curli major subunit CsgA and failed to produce curli based on CR binding. Mutation of purF (the first gene in the purine biosynthesis pathway) and rcpA also led to attenuated colonization of the mouse bladder. Overall, this work has provided new insight into the regulation of curli and the role of these amyloid fibers in UPEC biofilm formation and pathogenesis.IMPORTANCE Uropathogenic Escherichia coli (UPEC) strains are the most common cause of urinary tract infection, a disease increasingly associated with escalating antibiotic resistance. UPEC strains possess multiple surface-associated factors that enable their colonization of the urinary tract, including fimbriae, curli, and autotransporters. Curli are extracellular amyloid fibers that enhance UPEC virulence and promote biofilm formation. Here we examined the function and regulation of curli in a UPEC pyelonephritis strain belonging to the highly virulent O45:K1:H7 neonatal meningitis-associated clone. Curli expression at human physiological temperature led to increased biofilm formation, resistance of sessile cells to the human cationic peptide LL-37, and enhanced bladder colonization. Using a comprehensive genetic screen, we identified multiple genes involved in curli production, including several that were novel or poorly characterized with respect to curli synthesis. In total, this study demonstrates an important role for curli as a UPEC virulence factor that promotes biofilm formation, resistance, and pathogenesis. Copyright © 2018 Nhu et al.


September 22, 2019  |  

Population genomics of Culiseta melanura, the principal vector of Eastern equine encephalitis virus in the United States.

Eastern Equine Encephalitis (EEE) (Togaviridae, Alphavirus) is a highly pathogenic mosquito-borne arbovirus that circulates in an enzootic cycle involving Culiseta melanura mosquitoes and wild Passeriformes birds in freshwater swamp habitats. Recently, the northeastern United States has experienced an intensification of virus activity with increased human involvement and northward expansion into new regions. In addition to its principal role in enzootic transmission of EEE virus among avian hosts, recent studies on the blood-feeding behavior of Cs. melanura throughout its geographic range suggest that this mosquito may also be involved in epizootic / epidemic transmission to equines and humans in certain locales. Variations in blood feeding behavior may be a function of host availability, environmental factors, and/or underlying genetic differences among regional populations. Despite the importance of Cs. melanura in transmission and maintenance of EEE virus, the genetics of this species remains largely unexplored.To investigate the occurrence of genetic variation in Cs. melanura, the genome of this mosquito vector was sequenced resulting in a draft genome assembly of 1.28 gigabases with a contig N50 of 93.36 kilobases. Populations of Cs. melanura from 10 EEE virus foci in the eastern North America were genotyped with double-digest RAD-seq. Following alignment of reads to the reference genome, variant calling, and filtering, 40,384 SNPs were retained for downstream analyses. Subsequent analyses revealed genetic differentiation between northern and southern populations of this mosquito species. Moreover, limited fine-scale population structure was detected throughout northeastern North America, suggesting local differentiation of populations but also a history of ancestral polymorphism or contemporary gene flow. Additionally, a genetically distinct cluster was identified predominantly at two northern sites.This study elucidates the first evidence of fine-scale population structure in Cs. melanura throughout its eastern range and detects evidence of gene flow between populations in northeastern North America. This investigation provides the groundwork for examining the consequences of genetic variations in the populations of this mosquito species that could influence vector-host interactions and the risk of human and equine infection with EEE virus.


September 22, 2019  |  

Comparative genomics of Salmonella enterica serovar Montevideo reveals lineage-specific gene differences that may influence ecological niche association.

Salmonella enterica serovar Montevideo has been linked to recent foodborne illness outbreaks resulting from contamination of products such as fruits, vegetables, seeds and spices. Studies have shown that Montevideo also is frequently associated with healthy cattle and can be isolated from ground beef, yet human salmonellosis outbreaks of Montevideo associated with ground beef contamination are rare. This disparity fuelled our interest in characterizing the genomic differences between Montevideo strains isolated from healthy cattle and beef products, and those isolated from human patients and outbreak sources. To that end, we sequenced 13 Montevideo strains to completion, producing high-quality genome assemblies of isolates from human patients (n=8) or from healthy cattle at slaughter (n=5). Comparative analysis of sequence data from this study and publicly available sequences (n=72) shows that Montevideo falls into four previously established clades, differentially occupied by cattle and human strains. The results of these analyses reveal differences in metabolic islands, environmental adhesion determinants and virulence factors within each clade, and suggest explanations for the infrequent association between bovine isolates and human illnesses.


September 22, 2019  |  

Discovery of multi-drug resistant, MCR-1 and ESBL-coproducing ST117 Escherichia coli from diseased chickens in Northeast China

An endemic multi-drug resistant ST117 E. coli isolate coproducing MCR-1 and 3 ESBL loci was, for the first time, detected from diseased chicken, Liaoning Province, in Northeast China, from 2011 to 2012. Whole-genome sequencing revealed 5 unique plasmids, namely pHXH-1, pHXH-2, pHXH-3, pHXH-4 and pHXH-5). Among them, pHXH1 and pHXH4 encode ESBL, and pHXH-5 mediates MCR-1 colistin resistance. The results indicate that the potentially-national dissemination of MCR-1-positive pathogens with pan-drug resistance proceeds via food chains.


September 22, 2019  |  

Genomic analysis of multidrug-resistant Escherichia coli ST58 causing urosepsis.

Sequence type 58 (ST58) phylogroup B1 Escherichia coli have been isolated from a wide variety of mammalian and avian hosts but are not noted for their ability to cause serious disease in humans or animals. Here we determined the genome sequences of two multidrug-resistant E. coli ST58 strains from urine and blood of one patient using a combination of Illumina and Single Molecule, Real-Time (SMRT) sequencing. Both ST58 strains were clonal and were characterised as serotype O8:H25, phylogroup B1 and carried a complex resistance locus/loci (CRL) that featured an atypical class 1 integron with a dfrA5 (trimethoprim resistance) gene cassette followed by only 24 bp of the 3′-CS. CRL that carry this particular integron have been described previously in E. coli from cattle, pigs and humans in Australia. The integron abuts a copy of Tn6029, an IS26-flanked composite transposon encoding blaTEM, sul2 and strAB genes that confer resistance to ampicillin, sulfathiazole and streptomycin, respectively. The CRL resides within a novel Tn2610-like hybrid Tn1721/Tn21 transposon on an IncF, ColV plasmid (pSDJ2009-52F) of 138 553 bp that encodes virulence associated genes implicated in life-threatening extraintestinal pathogenic E. coli (ExPEC) infections. Notably, pSDJ2009-52F shares high sequence identity with pSF-088-1, a plasmid reported in an E. coli ST95 strain from a patient with blood sepsis from a hospital in San Francisco. These data suggest that extraintestinal infections caused by E. coli carrying ColV-like plasmids, irrespective of their phylogroup or ST, may pose a potential threat to human health, particularly to the elderly and immunocompromised. Copyright © 2018. Published by Elsevier B.V.


September 22, 2019  |  

Dissemination and persistence of extended-spectrum cephalosporin-resistance encoding IncI1-blaCTXM-1 plasmid among Escherichia coli in pigs.

This study investigated the ecology, epidemiology and plasmid characteristics of extended-spectrum cephalosporin (ESC)-resistant E. coli in healthy pigs over a period of 4 years (2013-2016) following the withdrawal of ESCs. High carriage rates of ESC-resistant E. coli were demonstrated in 2013 (86.6%) and 2014 (83.3%), compared to 2015 (22%) and 2016 (8.5%). ESC resistance identified among E. coli isolates was attributed to the carriage of an IncI1 ST-3 plasmid (pCTXM1-MU2) encoding blaCTXM-1. Genomic characterisation of selected E. coli isolates (n?=?61) identified plasmid movement into multiple commensal E. coli (n?=?22 STs). Major STs included ST10, ST5440, ST453, ST2514 and ST23. A subset of the isolates belong to the atypical enteropathogenic E. coli (aEPEC) pathotype that harboured multiple LEE pathogenic islands. pCTXM1-MU2 was similar (99% nt identity) to IncI1-ST3 plasmids reported from Europe, encoded resistance to aminoglycosides, sulphonamides and trimethoprim, and carried colicin Ib. pCTXM1-MU2 appears to be highly stable and readily transferable. This study demonstrates that ESC resistance may persist for a protracted period following removal of direct selection pressure, resulting in the emergence of ESC-resistance in both commensal E. coli and aEPEC isolates of potential significance to human and animal health.


September 22, 2019  |  

Discovery of mcr-1-mediated colistin resistance in a highly virulent Escherichia coli lineage.

Resistance to last-line polymyxins mediated by the plasmid-borne mobile colistin resistance gene (mcr-1) represents a new threat to global human health. Here we present the complete genome sequence of an mcr-1-positive multidrug-resistant Escherichia coli strain (MS8345). We show that MS8345 belongs to serotype O2:K1:H4, has a large 241,164-bp IncHI2 plasmid that carries 15 other antibiotic resistance genes (including the extended-spectrum ß-lactamase blaCTX-M-1) and 3 putative multidrug efflux systems, and contains 14 chromosomally encoded antibiotic resistance genes. MS8345 also carries a large ColV-like virulence plasmid that has been associated with E. coli bacteremia. Whole-genome phylogeny revealed that MS8345 clusters within a discrete clade in the sequence type 95 (ST95) lineage, and MS8345 is very closely related to the highly virulent O45:K1:H4 clone associated with neonatal meningitis. Overall, the acquisition of a plasmid carrying resistance to colistin and multiple other antibiotics in this virulent E. coli lineage is concerning and might herald an era where the empirical treatment of ST95 infections becomes increasingly more difficult.IMPORTANCEEscherichia coli ST95 is a globally disseminated clone frequently associated with bloodstream infections and neonatal meningitis. However, the ST95 lineage is defined by low levels of drug resistance amongst clinical isolates, which normally provides for uncomplicated treatment options. Here, we provide the first detailed genomic analysis of an E. coli ST95 isolate that has both high virulence potential and resistance to multiple antibiotics. Using the genome, we predicted its virulence and antibiotic resistance mechanisms, which include resistance to last-line antibiotics mediated by the plasmid-borne mcr-1 gene. Finding an ST95 isolate resistant to nearly all antibiotics that also has a high virulence potential is of major clinical importance and underscores the need to monitor new and emerging trends in antibiotic resistance development in this important global lineage. Copyright © 2018 Forde et al.


September 22, 2019  |  

Antimicrobial resistance profile of mcr-1 positive clinical isolates of Escherichia coli in China From 2013 to 2016.

Multidrug-resistant (MDR) Escherichia coli poses a great challenge for public health in recent decades. Polymyxins have been reconsidered as a valuable therapeutic option for the treatment of infections caused by MDR E. coli. A plasmid-encoded colistin resistance gene mcr-1 encoding phosphoethanolamine transferase has been recently described in Enterobacteriaceae. In this study, a total of 123 E. coli isolates obtained from patients with diarrheal diseases in China were used for the genetic analysis of colistin resistance in clinical isolates. Antimicrobial resistance profile of polymyxin B (PB) and 11 commonly used antimicrobial agents were determined. Among the 123 E. coli isolates, 9 isolates (7.3%) were resistant to PB and PCR screening showed that seven (5.7%) isolates carried the mcr-1 gene. A hybrid sequencing analysis using single-molecule, real-time (SMRT) sequencing and Illumina sequencing was then performed to resolve the genomes of the seven mcr-1 positive isolates. These seven isolates harbored multiple plasmids and are MDR, with six isolates carrying one mcr-1 positive plasmid and one isolate (14EC033) carrying two mcr-1 positive plasmids. These eight mcr-1 positive plasmids belonged to the IncX4, IncI2, and IncP1 types. In addition, the mcr-1 gene was the solo antibiotic resistance gene identified in the mcr-1 positive plasmids, while the rest of the antibiotic resistance genes were mostly clustered into one or two plasmids. Interestingly, one mcr-1 positive isolate (14EC047) was susceptible to PB, and we showed that the activity of MCR-1-mediated colistin resistance was not phenotypically expressed in 14EC047 host strain. Furthermore, three isolates exhibited resistance to PB but did not carry previously reported mcr-related genes. Multilocus sequence typing (MLST) showed that these mcr-1 positive E. coli isolates belonged to five different STs, and three isolates belonged to ST301 which carried multiple virulence factors related to diarrhea. Additionally, the mcr-1 positive isolates were all susceptible to imipenem (IMP), suggesting that IMP could be used to treat infection caused by mcr-1 positive E. coli isolates. Collectively, this study showed a high occurrence of mcr-1 positive plasmids in patients with diarrheal diseases of Guangzhou in China and the abolishment of the MCR-1 mediated colistin resistance in one E. coli isolate.


September 22, 2019  |  

Understanding explosive diversification through cichlid fish genomics.

Owing to their taxonomic, phenotypic, ecological and behavioural diversity and propensity for explosive diversification, the assemblages of cichlid fish in the East African Great Lakes Victoria, Malawi and Tanganyika are important role models in evolutionary biology. With the release of five reference genomes and many additional genomic resources, as well as the establishment of functional genomic tools, the cichlid system has fully entered the genomic era. The in-depth genomic exploration of the East African cichlid fauna – in combination with the examination of their ecology, morphology and behaviour – permits novel insights into the way organisms diversify.


September 22, 2019  |  

How complete are “complete” genome assemblies?-An avian perspective.

The genomics revolution has led to the sequencing of a large variety of nonmodel organisms often referred to as “whole” or “complete” genome assemblies. But how complete are these, really? Here, we use birds as an example for nonmodel vertebrates and find that, although suitable in principle for genomic studies, the current standard of short-read assemblies misses a significant proportion of the expected genome size (7% to 42%; mean 20 ± 9%). In particular, regions with strongly deviating nucleotide composition (e.g., guanine-cytosine-[GC]-rich) and regions highly enriched in repetitive DNA (e.g., transposable elements and satellite DNA) are usually underrepresented in assemblies. However, long-read sequencing technologies successfully characterize many of these underrepresented GC-rich or repeat-rich regions in several bird genomes. For instance, only ~2% of the expected total base pairs are missing in the last chicken reference (galGal5). These assemblies still contain thousands of gaps (i.e., fragmented sequences) because some chromosomal structures (e.g., centromeres) likely contain arrays of repetitive DNA that are too long to bridge with currently available technologies. We discuss how to minimize the number of assembly gaps by combining the latest available technologies with complementary strengths. At last, we emphasize the importance of knowing the location, size and potential content of assembly gaps when making population genetic inferences about adjacent genomic regions.© 2018 The Authors. Molecular Ecology Resources Published by John Wiley & Sons Ltd.


Talk with an expert

If you have a question, need to check the status of an order, or are interested in purchasing an instrument, we're here to help.