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July 7, 2019

Complete genome sequence of a new halophilic archaeon, Haloarcula taiwanensis, isolated from a solar saltern in southern Taiwan.

We report here the completion of the genome sequence of a new species of haloarchaea, Haloarcula taiwanensis, isolated in southern Taiwan. The 3,721,706-bp genome consisted of chromosome I (2,966,258 bp, 63.6% GC content), chromosome II (525,233 bp, 59.6% GC content), plasmid pNYT1 (129,893 bp, 55.3% GC content), and plasmid pNYT2 (100,322 bp, 55.7% GC content).


July 7, 2019

Complete genome sequence of Pseudomonas sp. strain NC02, isolated from soil.

We report here the complete genome sequence of Pseudomonas sp. strain NC02, isolated from soil in eastern Massachusetts. We assembled PacBio reads into a single closed contig with 132× mean coverage and then polished this contig using Illumina MiSeq reads, yielding a 6,890,566-bp sequence with 61.1% GC content. Copyright © 2018 Cerra et al.


July 7, 2019

Complete genome sequence of Escherichia coli ML35.

We report here the complete genome sequence of Escherichia coli strain ML35. We assembled PacBio reads into a single closed contig with 169× mean coverage and then polished this contig using Illumina MiSeq reads, yielding a 4,918,774-bp sequence with 50.8% GC content. Copyright © 2018 Casale et al.


July 7, 2019

Genome sequence of the necrotrophic plant pathogen Alternaria brassicicola Abra43.

Alternaria brassicicola causes dark spot (or black spot) disease, which is one of the most common and destructive fungal diseases of Brassicaceae spp. worldwide. Here, we report the draft genome sequence of strain Abra43. The assembly comprises 29 scaffolds, with an N50 value of 2.1 Mb. The assembled genome was 31,036,461 bp in length, with a G+C content of 50.85%.


July 7, 2019

An empirical evaluation of error correction methods and tools for next generation sequencing data

esearch. However, data produced by NGS is affected by different errors such as substitutions, deletions or insertion. It is essential to differentiate between true biological variants and alterations occurred due to errors for accurate downstream analysis. Many types of methods and tools have been developed for NGS error correction. Some of these methods only correct substitutions errors whereas others correct multi types of data errors. In this article, a comprehensive evaluation of three types of methods (k-spectrum based, Multi- sequencing alignment and Hybrid based) is presented which are implemented and adopted by different tools. Experiments have been conducted to compare the performance based on runtime and error correction rate. Two different computing platforms have been used for the experiments to evaluate effectiveness of runtime and error correction rate. The mission and aim of this comparative evaluation is to provide recommendations for selection of suitable tools to cope with the specific needs of users and practitioners. It has been noticed that k-mer spectrum based methodology generated superior results as compared to other methods. Amongst all the tools being utilized, Racer has shown eminent performance in terms of error correction rate and execution time for both small as well as large data sets. In multisequence alignment based tools, Karect depicts excellent error correction rate whereas Coral shows better execution time for all data sets. In hybrid based tools, Jabba shows better error correction rate and execution time as compared to brownie. Computing platforms mostly affect execution time but have no general effect on error correction rate.


July 7, 2019

Ten steps to get started in Genome Assembly and Annotation.

As a part of the ELIXIR-EXCELERATE efforts in capacity building, we present here 10 steps to facilitate researchers getting started in genome assembly and genome annotation. The guidelines given are broadly applicable, intended to be stable over time, and cover all aspects from start to finish of a general assembly and annotation project. Intrinsic properties of genomes are discussed, as is the importance of using high quality DNA. Different sequencing technologies and generally applicable workflows for genome assembly are also detailed. We cover structural and functional annotation and encourage readers to also annotate transposable elements, something that is often omitted from annotation workflows. The importance of data management is stressed, and we give advice on where to submit data and how to make your results Findable, Accessible, Interoperable, and Reusable (FAIR).


July 7, 2019

FMLRC: Hybrid long read error correction using an FM-index.

Long read sequencing is changing the landscape of genomic research, especially de novo assembly. Despite the high error rate inherent to long read technologies, increased read lengths dramatically improve the continuity and accuracy of genome assemblies. However, the cost and throughput of these technologies limits their application to complex genomes. One solution is to decrease the cost and time to assemble novel genomes by leveraging “hybrid” assemblies that use long reads for scaffolding and short reads for accuracy.We describe a novel method leveraging a multi-string Burrows-Wheeler Transform with auxiliary FM-index to correct errors in long read sequences using a set of complementary short reads. We demonstrate that our method efficiently produces significantly more high quality corrected sequence than existing hybrid error-correction methods. We also show that our method produces more contiguous assemblies, in many cases, than existing state-of-the-art hybrid and long-read only de novo assembly methods.Our method accurately corrects long read sequence data using complementary short reads. We demonstrate higher total throughput of corrected long reads and a corresponding increase in contiguity of the resulting de novo assemblies. Improved throughput and computational efficiency than existing methods will help better economically utilize emerging long read sequencing technologies.


July 7, 2019

The odyssey of the ancestral Escherich strain through culture collections: an example of allopatric diversification.

More than a century ago, Theodor Escherich isolated the bacterium that was to become Escherichia coli, one of the most studied organisms. Not long after, the strain began an odyssey and landed in many laboratories across the world. As laboratory culture conditions could be responsible for major changes in bacterial strains, we conducted a genome analysis of isolates of this emblematic strain from different culture collections (England, France, the United States, Germany). Strikingly, many discrepancies between the isolates were observed, as revealed by multilocus sequence typing (MLST), the presence of virulence-associated genes, core genome MLST, and single nucleotide polymorphism/indel analyses. These differences are correlated with the phylogeographic history of the strain and were due to an unprecedented number of mutations in coding DNA repair functions such as mismatch repair (MutL) and oxidized guanine nucleotide pool cleaning (MutT), conferring a specific mutational spectrum and leading to a mutator phenotype. The mutator phenotype was probably acquired during subculturing and corresponded to second-order selection. Furthermore, all of the isolates exhibited hypersusceptibility to antibiotics due to mutations in efflux pump- and porin-encoding genes, as well as a specific mutation in the sigma factor-encoding generpoS. These defects reflect a self-preservation and nutritional competence tradeoff allowing survival under the starvation conditions imposed by storage. From a clinical point of view, dealing with such mutator strains can lead microbiologists to draw false conclusions about isolate relatedness and may impact therapeutic effectiveness. IMPORTANCE Mutator phenotypes have been described in laboratory-evolved bacteria, as well as in natural isolates. Several genes can be impacted, each of them being associated with a typical mutational spectrum. By studying one of the oldest strains available, the ancestral Escherich strain, we were able to identify its mutator status leading to tremendous genetic diversity among the isolates from various collections and allowing us to reconstruct the phylogeographic history of the strain. This mutator phenotype was probably acquired during the storage of the strain, promoting adaptation to a specific environment. Other mutations inrpoSand efflux pump- and porin-encoding genes highlight the acclimatization of the strain through self-preservation and nutritional competence regulation. This strain history can be viewed as unintentional experimental evolution in culture collections all over the word since 1885, mimicking the long-term experimental evolution ofE. coliof Lenski et al. (O. Tenaillon, J. E. Barrick, N. Ribeck, D. E. Deatherage, J. L. Blanchard, A. Dasgupta, G. C. Wu, S. Wielgoss, S. Cruveiller, C. Médigue, D. Schneider, and R. E. Lenski, Nature 536:165-170, 2016, https://doi.org/10.1038/nature18959) that shares numerous molecular features.


July 7, 2019

Complete genome sequence of uropathogenic Escherichia coli isolate UPEC 26-1.

Urinary tract infections (UTIs) are among the most common infections in humans, predominantly caused by uropathogenic Escherichia coli (UPEC). The diverse genomes of UPEC strains mostly impede disease prevention and control measures. In this study, we comparatively analyzed the whole genome sequence of a highly virulent UPEC strain, namely UPEC 26-1, which was isolated from urine sample of a patient suffering from UTI in Korea. Whole genome analysis showed that the genome consists of one circular chromosome of 5,329,753 bp, comprising 5064 protein-coding genes, 122 RNA genes (94 tRNA, 22 rRNA and 6 ncRNA genes), and 100 pseudogenes, with an average G+C content of 50.56%. In addition, we identified 8 prophage regions comprising 5 intact, 2 incomplete and 1 questionable ones and 63 genomic islands, suggesting the possibility of horizontal gene transfer in this strain. Comparative genome analysis of UPEC 26-1 with the UPEC strain CFT073 revealed an average nucleotide identity of 99.7%. The genome comparison with CFT073 provides major differences in the genome of UPEC 26-1 that would explain its increased virulence and biofilm formation. Nineteen of the total GIs were unique to UPEC 26-1 compared to CFT073 and nine of them harbored unique genes that are involved in virulence, multidrug resistance, biofilm formation and bacterial pathogenesis. The data from this study will assist in future studies of UPEC strains to develop effective control measures.


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