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July 7, 2019

LongISLND: in silico sequencing of lengthy and noisy datatypes.

LongISLND is a software package designed to simulate sequencing data according to the characteristics of third generation, single-molecule sequencing technologies. The general software architecture is easily extendable, as demonstrated by the emulation of Pacific Biosciences (PacBio) multi-pass sequencing with P5 and P6 chemistries, producing data in FASTQ, H5, and the latest PacBio BAM format. We demonstrate its utility by downstream processing with consensus building and variant calling.LongISLND is implemented in Java and available at http://bioinform.github.io/longislnd CONTACT: hugo.lam@roche.comSupplementary information: Supplementary data are available at Bioinformatics online.© The Author 2016. Published by Oxford University Press.

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July 7, 2019

Novel m4C modification in type I restriction-modification systems.

We identify a new subgroup of Type I Restriction-Modification enzymes that modify cytosine in one DNA strand and adenine in the opposite strand for host protection. Recognition specificity has been determined for ten systems using SMRT sequencing and each recognizes a novel DNA sequence motif. Previously characterized Type I systems use two identical copies of a single methyltransferase (MTase) subunit, with one bound at each half site of the specificity (S) subunit to form the MTase. The new m4C-producing Type I systems we describe have two separate yet highly similar MTase subunits that form a heterodimeric M1M2S MTase. The MTase subunits from these systems group into two families, one of which has NPPF in the highly conserved catalytic motif IV and modifies adenine to m6A, and one having an NPPY catalytic motif IV and modifying cytosine to m4C. The high degree of similarity among their cytosine-recognizing components (MTase and S) suggest they have recently evolved, most likely from the far more common m6A Type I systems. Type I enzymes that modify cytosine exclusively were formed by replacing the adenine target recognition domain (TRD) with a cytosine-recognizing TRD. These are the first examples of m4C modification in Type I RM systems.© The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

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July 7, 2019

Emergence of endemic MLST non-typeable vancomycin-resistant Enterococcus faecium.

Enterococcus faecium is a major nosocomial pathogen causing significant morbidity and mortality worldwide. Assessment of E. faecium using MLST to understand the spread of this organism is an important component of hospital infection control measures. Recent studies, however, suggest that MLST might be inadequate for E. faecium surveillance.To use WGS to characterize recently identified vancomycin-resistant E. faecium (VREfm) isolates non-typeable by MLST that appear to be causing a multi-jurisdictional outbreak in Australia.Illumina NextSeq and Pacific Biosciences SMRT sequencing platforms were used to determine the genome sequences of 66 non-typeable E. faecium (NTEfm) isolates. Phylogenetic and bioinformatics analyses were subsequently performed using a number of in silico tools.Sixty-six E. faecium isolates were identified by WGS from multiple health jurisdictions in Australia that could not be typed by MLST due to a missing pstS allele. SMRT sequencing and complete genome assembly revealed a large chromosomal rearrangement in representative strain DMG1500801, which likely facilitated the deletion of the pstS region. Phylogenomic analysis of this population suggests that deletion of pstS within E. faecium has arisen independently on at least three occasions. Importantly, the majority of these isolates displayed a vancomycin-resistant genotype.We have identified NTEfm isolates that appear to be causing a multi-jurisdictional outbreak in Australia. Identification of these isolates has important implications for MLST-based typing activities designed to monitor the spread of VREfm and provides further evidence supporting the use of WGS for hospital surveillance of E. faecium.© The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

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July 7, 2019

Divergent isoprenoid biosynthesis pathways in Staphylococcus species constitute a drug target for treating infections in companion animals.

Staphylococcus species are a leading cause of skin and soft tissue infections in humans and animals, and the antibiotics used to treat these infections are often the same. Methicillin- and multidrug-resistant staphylococcal infections are becoming more common in human and veterinary medicine. From a “One Health” perspective, this overlap in antibiotic use and resistance raises concerns over the potential spread of antibiotic resistance genes. Whole-genome sequencing and comparative genomics analysis revealed that Staphylococcus species use divergent pathways to synthesize isoprenoids. Species frequently associated with skin and soft tissue infections in companion animals, including S. schleiferi and S. pseudintermedius, use the nonmevalonate pathway. In contrast, S. aureus, S. epidermidis, and S. lugdunensis use the mevalonate pathway. The antibiotic fosmidomycin, an inhibitor of the nonmevalonate pathway, was effective in killing canine clinical staphylococcal isolates but had no effect on the growth or survival of S. aureus and S. epidermidis. These data identify an essential metabolic pathway in Staphylococcus that differs among members of this genus and suggest that drugs such as fosmidomycin, which targets enzymes in the nonmevalonate pathway, may be an effective treatment for certain staphylococcal infections. IMPORTANCE Drug-resistant Staphylococcus species are a major concern in human and veterinary medicine. There is a need for new antibiotics that exhibit a selective effect in treating infections in companion and livestock animals and that would not be used to treat human bacterial infections. We have identified fosmidomycin as an antibiotic that selectively targets certain Staphylococcus species that are often encountered in skin infections in cats and dogs. These findings expand our understanding of Staphylococcus evolution and may have direct implications for treating staphylococcal infections in veterinary medicine.

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July 7, 2019

ChIP-Seq-annotated Heliconius erato genome highlights patterns of cis-regulatory evolution in Lepidoptera.

Uncovering phylogenetic patterns of cis-regulatory evolution remains a fundamental goal for evolutionary and developmental biology. Here, we characterize the evolution of regulatory loci in butterflies and moths using chromatin immunoprecipitation sequencing (ChIP-seq) annotation of regulatory elements across three stages of head development. In the process we provide a high-quality, functionally annotated genome assembly for the butterfly, Heliconius erato. Comparing cis-regulatory element conservation across six lepidopteran genomes, we find that regulatory sequences evolve at a pace similar to that of protein-coding regions. We also observe that elements active at multiple developmental stages are markedly more conserved than elements with stage-specific activity. Surprisingly, we also find that stage-specific proximal and distal regulatory elements evolve at nearly identical rates. Our study provides a benchmark for genome-wide patterns of regulatory element evolution in insects, and it shows that developmental timing of activity strongly predicts patterns of regulatory sequence evolution. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

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July 7, 2019

The complete genome of Dietzia timorensis ID05-A0528(T) revealed the genetic basis for its saline-alkali tolerance.

The type strain Dietzia timorensis ID05-A0528(T), was reported to be able to survive in the highly saline and alkaline environments with diverse carbon sources. In order to more pertinently understand the genetic mechanisms of its environmental tolerance and crude oil emulsification, we reported the complete genome sequence of the strain in the study. The genome contains only one circular chromosome, with the total size of 3,607,892 bps, and the G+C content of this strain is 65.58%, much lower than other type strains of this genus. It was found that strain ID05-A0528(T) contains genes involved in transportation and biosynthesis of compatible solutes, as well as genes encoding monovalent cation/proton antiporters, which could explain its abilities to tolerate high salinity and alkalinity. Various central metabolic routes and complete alkane hydroxylation pathway were also identified in the genome of strain ID05-A0528(T), which is in accordance with its ability to use a wide spectrum of carbon sources and to degrade n-alkanes. Copyright © 2016. Published by Elsevier B.V.

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July 7, 2019

Silicon content of individual cells of Synechococcus from the North Atlantic Ocean

The widely distributed marine cyanobacterium Synechococcus is thought to exert an influence on the marine silicon (Si) cycle through its high cellular Si relative to organic content. There are few measurements of Si in natural populations of Synechococcus, however, and the degree to which Synechococcus from various oligotrophic field sites and depths accumulate the element is unknown. We used synchrotron x-ray fluorescence to measure Si quotas in individual Synechococcus cells collected during three cruises in the western North Atlantic Ocean in the summer and fall, focusing on cells from the surface mixed layer (SML; <10 m) and the deep chlorophyll maximum (DCM). Individual cell quotas varied widely, from 1 to 4700 amol Si cell- 1, though the middle 50% of quotas ranged between 17 and 119 amol Si cell- 1. Mean station-specific quotas exhibited an even narrower range of 31–72 amol Si cell- 1. No significant differences in Si quotas were observed across cruises or among stations, and no effect of ambient silicic acid concentration on quotas was observed within the narrow range of silicic acid concentrations encountered (0.6–1.3 µM). Despite this small range in ambient silicic acid, cells collected from the SML had an average of two-fold more Si than cells collected from the DCM. Differences in Si content with depth may be related to observed differences in the dominant Synechococcus clades between the SML and DCM habitats, determined by petB gene sequencing.

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July 7, 2019

Key experimental evidence of chromosomal DNA transfer among selected tuberculosis-causing mycobacteria.

Horizontal gene transfer (HGT) is a major driving force of bacterial diversification and evolution. For tuberculosis-causing mycobacteria, the impact of HGT in the emergence and distribution of dominant lineages remains a matter of debate. Here, by using fluorescence-assisted mating assays and whole genome sequencing, we present unique experimental evidence of chromosomal DNA transfer between tubercle bacilli of the early-branching Mycobacterium canettii clade. We found that the obtained recombinants had received multiple donor-derived DNA fragments in the size range of 100 bp to 118 kbp, fragments large enough to contain whole operons. Although the transfer frequency between M. canettii strains was low and no transfer could be observed among classical Mycobacterium tuberculosis complex (MTBC) strains, our study provides the proof of concept for genetic exchange in tubercle bacilli. This outstanding, now experimentally validated phenomenon presumably played a key role in the early evolution of the MTBC toward pathogenicity. Moreover, our findings also provide important information for the risk evaluation of potential transfer of drug resistance and fitness mutations among clinically relevant mycobacterial strains.

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July 7, 2019

Whole genome sequence analysis indicates recent diversification of mammal-associated Campylobacter fetus and implicates a genetic factor associated with H2S production.

Campylobacter fetus (C. fetus) can cause disease in both humans and animals. C. fetus has been divided into three subspecies: C. fetus subsp. fetus (Cff), C. fetus subsp. venerealis (Cfv) and C. fetus subsp. testudinum (Cft). Subspecies identification of mammal-associated C. fetus strains is crucial in the control of Bovine Genital Campylobacteriosis (BGC), a syndrome associated with Cfv. The prescribed methods for subspecies identification of the Cff and Cfv isolates are: tolerance to 1 % glycine and H2S production.In this study, we observed the deletion of a putative cysteine transporter in the Cfv strains, which are not able to produce H2S from L-cysteine. Phylogenetic reconstruction of the core genome single nucleotide polymorphisms (SNPs) within Cff and Cfv strains divided these strains into five different clades and showed that the Cfv clade and a Cff clade evolved from a single Cff ancestor.Multiple C. fetus clades were observed, which were not consistent with the biochemical differentiation of the strains. This suggests the need for a closer evaluation of the current C. fetus subspecies differentiation, considering that the phenotypic differentiation is still applied in BGC control programs.

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July 7, 2019

Genome and plasmid analysis of blaIMP-4 -carrying Citrobacter freundii B38.

Sequencing of the blaIMP-4 -carrying C. freundii B38 using PacBio SMRT technique revealed that the genome contained a chromosome of 5,134,500 bp, and three plasmids, pOZ172 (127,005 bp), pOZ181 (277,592 bp), and pOZ182 (18,467 bp). Plasmid pOZ172 was identified as IncFIIY, like pP10164-NDM and pNDM-EcGN174. It carries a class 1 integron with four cassettes: blaIMP-4-qacG2-aacA4-aphA15, and a complete hybrid tni module (tniR-tniQ-tniB-tniA). The recombination of tniR from Tn402 (identical) with tniQBA (99%) from Tn5053 occurred within the res site of Tn402/5053. The Tn402/5053-like integron, named Tn6017, was inserted into Tn1722 at the res II site. The replication, partitioning and transfer systems of pOZ181 were similar to IncHI2 (e.g. R478) and contained a sul1-type class 1 integron with the cassette array: orf-dfrA1-orf-gcu37-aadA5 linked to an upstream Tn1696 tnpA-tnpR and to a downstream 3′ CS and ISCR1 A Tn2 transposon with a blaTEM-1b ß-lactamase was identified on pOZ182. Other interesting resistance determinants on the B38 chromosome included MDR efflux pumps, AmpC ß-lactamase, and resistances to Cu, Ag, As, and Zn. This is the first report of a complete tni module linked to a blaIMP- 4 carrying class 1 integron, and together with other recently reported non-sul1 integrons, represents the emergence of a distinct evolutionary lineage of class 1 integrons lacking a 3′ -CS (qacE?1-sul1). The unique cassette array, complete tni module of Tn6017, and incompatibility group of pOZ172 suggests a different blaIMP-4 evolutionary pathway in C. freundii B38 compared to other blaIMP-4 foundin Gram-negative bacteria in the Western Pacific Region. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

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July 7, 2019

Tracking inter-institutional spread of NDM and identification of a novel NDM-positive plasmid, pSg1-NDM, using next-generation sequencing approaches.

Owing to gene transposition and plasmid conjugation, New Delhi metallo-ß-lactamase (NDM) is typically identified among varied Enterobacteriaceae species and STs. We used WGS to characterize the chromosomal and plasmid molecular epidemiology of NDM transmission involving four institutions in Singapore.Thirty-three Enterobacteriaceae isolates (collection years 2010-14) were sequenced using short-read sequencing-by-synthesis and analysed. Long-read single molecule, real-time sequencing (SMRTS) was used to characterize genetically a novel plasmid pSg1-NDM carried on Klebsiella pneumoniae ST147.In 20 (61%) isolates, blaNDM was located on the pNDM-ECS01 plasmid in the background of multiple bacterial STs, including eight K. pneumoniae STs and five Escherichia coli STs. In six (18%) isolates, a novel blaNDM-positive plasmid, pSg1-NDM, was found only in K. pneumoniae ST147. The pSg1-NDM-K. pneumoniae ST147 clone (Sg1-NDM) was fully sequenced using SMRTS. pSg1-NDM, a 90?103 bp IncR plasmid, carried genes responsible for resistance to six classes of antimicrobials. A large portion of pSg1-NDM had no significant homology to any known plasmids in GenBank. pSg1-NDM had no conjugative transfer region. Combined chromosomal-plasmid phylogenetic analysis revealed five clusters of clonal bacterial NDM-positive plasmid transmission, of which two were inter-institution clusters. The largest inter-institution cluster involved six K. pneumoniae ST147-pSg1-NDM isolates. Fifteen patients were involved in transmission clusters, of which four had ward contact, six had hospital contact and five had an unknown transmission link.A combined sequencing-by-synthesis and SMRTS approach can determine effectively the transmission clusters of blaNDM and genetically characterize novel plasmids. Plasmid molecular epidemiology is important to understanding NDM spread as blaNDM-positive plasmids can conjugate extensively across species and STs.© The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

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July 7, 2019

Genomic recombination leading to decreased virulence of group B Streptococcus in a mouse model of adult invasive disease.

Adult invasive disease caused by Group B Streptococcus (GBS) is increasing worldwide. Whole-genome sequencing (WGS) now permits rapid identification of recombination events, a phenomenon that occurs frequently in GBS. Using WGS, we described that strain NGBS375, a capsular serotype V GBS isolate of sequence type (ST)297, has an ST1 genomic background but has acquired approximately 300 kbp of genetic material likely from an ST17 strain. Here, we examined the virulence of this strain in an in vivo model of GBS adult invasive infection. The mosaic ST297 strain showed intermediate virulence, causing significantly less systemic infection and reduced mortality than a more virulent, serotype V ST1 isolate. Bacteremia induced by the ST297 strain was similar to that induced by a serotype III ST17 strain, which was the least virulent under the conditions tested. Yet, under normalized bacteremia levels, the in vivo intrinsic capacity to induce the production of pro-inflammatory cytokines was similar between the ST297 strain and the virulent ST1 strain. Thus, the diminished virulence of the mosaic strain may be due to reduced capacity to disseminate or multiply in blood during a systemic infection which could be mediated by regulatory factors contained in the recombined region.

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July 7, 2019

Probabilistic viral quasispecies assembly

Viruses are pathogens that cause infectious diseases. The swarm of virions is subject to the host’s immune pressure and possibly antiviral therapy. It may escape this selective pressure and gain selective advantage by acquiring one or more of the genomic alterations: single-nucleotide variants (SNVs), loss or gain of one or more amino acids, large deletions, for example, due to alternative splicing, or recombination of different strains. Genotypic antiretroviral drug resistance testing is performed via sequencing. Next-generation sequencing (NGS) technologies revolutionized assessing viral genetic diversity experimentally. In viral quasispecies analysis, there are two main goals: the identification of low-frequency variants and haplotype assembly on a whole-genome scale. PacBio performs single-molecule sequencing. This chapter elaborates human haplotyping and its relationship to probabilistic viral haplotype reconstruction methods. Viral quasispecies assembly has the potential to replace the current de facto diversity estimation by SNV calling. With advances in library preparation, increasing sensitivity of sequencing platforms, and more sophisticated models, it might be possible to detect all or most viral strains in a single individual.

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July 7, 2019

IncHI2 plasmids are the key vectors responsible for oqxAB transmission among Salmonella species.

This study reported and analysed the complete sequences of two oqxAB-bearing IncHI2 plasmids harboured by a clinical S. Typhimurium strain and an S. Indiana strain of animal origin, respectively. Particularly, pA3T recovered from S. Indiana comprised the resistance determinants oqxAB, aac(6′)Ib-cr, fosA3 and blaCTX-M-14 Further genetic screening of 63 oqxAB-positive Salmonella spp. isolates revealed that the majority carried IncHI2 plasmids, confirming that such plasmids play a pivotal role in dissemination of oqxAB in Salmonella spp.. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

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July 7, 2019

Multiplication of blaOXA-23 is common in clinical Acinetobacter baumannii, but does not enhance carbapenem resistance.

To investigate the copy number of blaOXA-23 and its correlation with carbapenem resistance in carbapenem-resistant Acinetobacter baumannii (CRAB).A total of 113 blaOXA-23-positive clinical CRAB isolates were collected from two hospitals in Zhejiang province, China. Their genetic relatedness was determined by MLST. The MIC of imipenem was determined using the agar diffusion method and the copy number of blaOXA-23 was measured using quantitative real-time PCR (qRT-PCR). The complete genomes of five clinical CRAB strains were sequenced using PacBio technology to investigate the multiplication mechanism of blaOXA-23.Most of the isolates (100/113) belonged to global clone II and the MIC of imipenem ranged from 16 to 96 mg/L. The gene blaOXA-23 resided exclusively in Tn2006 or Tn2009. Approximately 38% of the isolates carried two or more copies of blaOXA-23. The copy number of blaOXA-23 was not correlated with the MIC of imipenem. Within the five sequenced strains, multiple copies of blaOXA-23 were either tandemly clustered or independently inserted at different genomic sites.Multiplication of blaOXA-23 is common in CRAB, but does not enhance carbapenem resistance. Multiplication can be present in the form of either tandem amplifications or independent insertions at different sites.© The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

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