Menu
July 7, 2019

Structural variation analysis with strobe reads.

Structural variation including deletions, duplications and rearrangements of DNA sequence are an important contributor to genome variation in many organisms. In human, many structural variants are found in complex and highly repetitive regions of the genome making their identification difficult. A new sequencing technology called strobe sequencing generates strobe reads containing multiple subreads from a single contiguous fragment of DNA. Strobe reads thus generalize the concept of paired reads, or mate pairs, that have been routinely used for structural variant detection. Strobe sequencing holds promise for unraveling complex variants that have been difficult to characterize with current sequencing technologies.We introduce an algorithm for identification of structural variants using strobe sequencing data. We consider strobe reads from a test genome that have multiple possible alignments to a reference genome due to sequencing errors and/or repetitive sequences in the reference. We formulate the combinatorial optimization problem of finding the minimum number of structural variants in the test genome that are consistent with these alignments. We solve this problem using an integer linear program. Using simulated strobe sequencing data, we show that our algorithm has better sensitivity and specificity than paired read approaches for structural variation identification.braphael@brown.edu


July 7, 2019

Computational solutions to large-scale data management and analysis.

Today we can generate hundreds of gigabases of DNA and RNA sequencing data in a week for less than US$5,000. The astonishing rate of data generation by these low-cost, high-throughput technologies in genomics is being matched by that of other technologies, such as real-time imaging and mass spectrometry-based flow cytometry. Success in the life sciences will depend on our ability to properly interpret the large-scale, high-dimensional data sets that are generated by these technologies, which in turn requires us to adopt advances in informatics. Here we discuss how we can master the different types of computational environments that exist – such as cloud and heterogeneous computing – to successfully tackle our big data problems.


July 7, 2019

Complete mitogenome of Indian mottled eel, Anguilla bengalensis bengalensis (Gray, 1831) through PacBio RSII sequencing.

Complete mitogenome sequence for Anguilla bengalensis bengalensis (family Anguillidae) was generated through third-generation sequencing platform. The 16?714 bp mitgenome sequence contained 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs, and a non-coding (control) region. The gene order was identical to that observed in most of the other vertebrates. The comparison of complete mitogenome sequence of Indian mottled eel generated during this study with two other subspecies did not agree with the taxonomic status of the three subspecies and considered as one species.


July 7, 2019

Absence of genome reduction in diverse, facultative endohyphal bacteria.

Fungi interact closely with bacteria, both on the surfaces of the hyphae and within their living tissues (i.e. endohyphal bacteria, EHB). These EHB can be obligate or facultative symbionts and can mediate diverse phenotypic traits in their hosts. Although EHB have been observed in many lineages of fungi, it remains unclear how widespread and general these associations are, and whether there are unifying ecological and genomic features can be found across EHB strains as a whole. We cultured 11 bacterial strains after they emerged from the hyphae of diverse Ascomycota that were isolated as foliar endophytes of cupressaceous trees, and generated nearly complete genome sequences for all. Unlike the genomes of largely obligate EHB, the genomes of these facultative EHB resembled those of closely related strains isolated from environmental sources. Although all analysed genomes encoded structures that could be used to interact with eukaryotic hosts, pathways previously implicated in maintenance and establishment of EHB symbiosis were not universally present across all strains. Independent isolation of two nearly identical pairs of strains from different classes of fungi, coupled with recent experimental evidence, suggests horizontal transfer of EHB across endophytic hosts. Given the potential for EHB to influence fungal phenotypes, these genomes could shed light on the mechanisms of plant growth promotion or stress mitigation by fungal endophytes during the symbiotic phase, as well as degradation of plant material during the saprotrophic phase. As such, these findings contribute to the illumination of a new dimension of functional biodiversity in fungi.


July 7, 2019

Accurate selfcorrection of errors in long reads using de Bruijn graphs.

New long read sequencing technologies, like PacBio SMRT and Oxford NanoPore, can produce sequencing reads up to 50,000 bp long but with an error rate of at least 15%. Reducing the error rate is necessary for subsequent utilisation of the reads in, e.g., de novo genome assembly. The error correction problem has been tackled either by aligning the long reads against each other or by a hybrid approach that uses the more accurate short reads produced by second generation sequencing technologies to correct the long reads.We present an error correction method that uses long reads only. The method consists of two phases: first we use an iterative alignment-free correction method based on de Bruijn graphs with increasing length of k-mers, and second, the corrected reads are further polished using long-distance dependencies that are found using multiple alignments. According to our experiments the proposed method is the most accurate one relying on long reads only for read sets with high coverage. Furthermore, when the coverage of the read set is at least 75x, the throughput of the new method is at least 20% higher.LoRMA is freely available at http://www.cs.helsinki.fi/u/lmsalmel/LoRMA/ CONTACT: leena.salmela@cs.helsinki.fi. © The Author(s) 2016. Published by Oxford University Press.


July 7, 2019

Cultivation of a chemoautotroph from the SUP05 clade of marine bacteria that produces nitrite and consumes ammonium.

Marine oxygen minimum zones (OMZs) are expanding regions of intense nitrogen cycling. Up to half of the nitrogen available for marine organisms is removed from the ocean in these regions. Metagenomic studies have identified an abundant group of sulfur-oxidizing bacteria (SUP05) with the genetic potential for nitrogen cycling and loss in OMZs. However, SUP05 have defied cultivation and their physiology remains untested. We cultured, sequenced and tested the physiology of an isolate from the SUP05 clade. We describe a facultatively anaerobic sulfur-oxidizing chemolithoautotroph that produces nitrite and consumes ammonium under anaerobic conditions. Genetic evidence that closely related strains are abundant at nitrite maxima in OMZs suggests that sulfur-oxidizing chemoautotrophs from the SUP05 clade are a potential source of nitrite, fueling competing nitrogen removal processes in the ocean.


July 7, 2019

Enabling the democratization of the genomics revolution with a fully integrated web-based bioinformatics platform.

Continued advancements in sequencing technologies have fueled the development of new sequencing applications and promise to flood current databases with raw data. A number of factors prevent the seamless and easy use of these data, including the breadth of project goals, the wide array of tools that individually perform fractions of any given analysis, the large number of associated software/hardware dependencies, and the detailed expertise required to perform these analyses. To address these issues, we have developed an intuitive web-based environment with a wide assortment of integrated and cutting-edge bioinformatics tools in pre-configured workflows. These workflows, coupled with the ease of use of the environment, provide even novice next-generation sequencing users with the ability to perform many complex analyses with only a few mouse clicks and, within the context of the same environment, to visualize and further interrogate their results. This bioinformatics platform is an initial attempt at Empowering the Development of Genomics Expertise (EDGE) in a wide range of applications for microbial research.© The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.


July 7, 2019

Quantum changes in Helicobacter pylori gene expression accompany host-adaptation.

Helicobacter pylori is a highly successful gastric pathogen. High genomic plasticity allows its adaptation to changing host environments. Complete genomes of H. pylori clinical isolate UM032 and its mice-adapted serial derivatives 298 and 299, generated using both PacBio RS and Illumina MiSeq sequencing technologies, were compared to identify novel elements responsible for host-adaptation. The acquisition of a jhp0562-like allele, which encodes for a galactosyltransferase, was identified in the mice-adapted strains. Our analysis implies a new ß-1,4-galactosyltransferase role for this enzyme, essential for Ley antigen expression. Intragenomic recombination between babA and babB genes was also observed. Further, we expanded on the list of candidate genes whose expression patterns have been mediated by upstream homopolymer-length alterations to facilitate host adaption. Importantly, greater than four-fold reduction of mRNA levels was demonstrated in five genes. Among the down-regulated genes, three encode for outer membrane proteins, including BabA, BabB and HopD. As expected, a substantial reduction in BabA protein abundance was detected in mice-adapted strains 298 and 299 via Western analysis. Our results suggest that the expression of Ley antigen and reduced outer membrane protein expressions may facilitate H. pylori colonisation of mouse gastric epithelium.© The Author 2016. Published by Oxford University Press on behalf of Kazusa DNA Research Institute.


July 7, 2019

Implementation and data analysis of Tn-seq, whole genome resequencing, and single-molecule real time sequencing for bacterial genetics.

Few discoveries have been more transformative to the biological sciences than the development of DNA sequencing technologies. The rapid advancement of sequencing and bioinformatics tools has revolutionized bacterial genetics, deepening our understanding of model and clinically relevant organisms. Although application of newer sequencing technologies to studies in bacterial genetics is increasing, the implementation of DNA sequencing technologies and development of the bioinformatics tools required for analyzing the large data sets generated remains a challenge for many. In this minireview, we have chosen to summarize three sequencing approaches that are particularly useful for bacterial genetics. We provide resources for scientists new to and interested in their application. Herein, we discuss the analysis of Tn-seq data to determine gene disruptions differentially represented in a mutant population, Illumina sequencing for identification of suppressor or other mutations, and we summarize single-molecule real time (SMRT) sequencing for de novo genome assembly and the use of the output data for detection of DNA base modifications. Copyright © 2016, American Society for Microbiology. All Rights Reserved.


July 7, 2019

Development of new methods for the quantitative detection and typing of Lactobacillus parabuchneri in dairy products

Thirty-one isolates of Lactobacillus parabuchneri were obtained from cheese containing histamine; of these, 26 were found to possess the hdcA gene encoding histidine decarboxylase. By analysing the genome data of 13 isolates, specific targets for the development of PCR-based detection and typing systems for L. parabuchneri were identified. The real-time PCR for detection showed a linear quantification over a range of 7 logs and a detection limit of 10 gene equivalents per reaction. The strain typing method utilised the amplification of repeat sequences and showed discrimination comparable with a phylogenetic tree, based on genome comparisons. The method was suitable for detecting and monitoring the development of L. parabuchneri in raw milk and cheese.


July 7, 2019

Genomic analysis of the multi-drug-resistant clinical isolate Myroides odoratimimus PR63039.

Myroides odoratimimus (M. odoratimimus) has been gradually implicated as an important nosocomial pathogen that poses a serious health threat to immunocompromised patients owing to its multi-drug resistance. However, the resistance mechanism is currently unclear. To clarify the antibiotic resistance and infectivity mechanisms of M. odoratimimus, whole genome sequencing was performed on the multi-drug-resistant M. odoratimimus strain PR63039. The genome sequence was completed with single molecule real-time (SMRT) technologies. Then, annotation was performed using RAST and IMG-ER. A number of databases and software programs were used to analyze the genomic characteristics, including GC-Profile, ISfinder, CG viewer, ARDB, CARD, ResFinder, the VFDB database, PHAST and Progressive Mauve. The M. odoratimimus PR63039 genome consisted of a chromosome and a plasmid. The genome contained a large number of resistance genes and virulence factors. The distribution of the resistance genes was distinctive, and a resistance region named MY63039-RR was found. The subsystem features generated by RAST indicated that the annotated genome had 108 genes that were potentially involved in virulence, disease and defense, all of which had strong associations with resistance and pathogenicity. The prophage analysis showed two incomplete prophages in the genome. The genomic analysis of M. odoratimimus PR63039 partially clarified its antibiotic resistance mechanisms and virulence factors. Obtaining a clear understanding of its genomic characteristics will be conducive to the management of multidrug-resistant M. odoratimimus.


July 7, 2019

Current status of genome sequencing and its applications in aquaculture

Aquaculture is the fastest-growing food production sector in agriculture, with great potential to meet projected protein needs of human beings. Aquaculture is facing several challenges, including lack of a sufficient number of genetically improved species, lack of species-specific feeds, high mortality due to diseases and pollution of ecosystems. The rapid development of sequencing technologies has revolutionized biological sciences, and supplied necessary tools to tackle these challenges in aquaculture and thus ensure its sustainability and profitability. So far, draft genomes have been published in over 24 aquaculture species, and used to address important issues related to aquaculture. We briefly review the advances of next generation sequencing technologies, and summarize the status of whole genome sequencing and its general applications (i.e. establishing reference genomes and discovering DNA markers) and specific applications in tackling some important issues (e.g. breeding, diseases, sex determination & maturation) related to aquaculture. For sequencing a new genome, we recommend the use of 100–200 × short reads using Illumina and 50–60 × long reads with PacBio sequencing technologies. For identification of a large number of SNPs, resequencing pooled DNA samples from different populations is the most cost-effective way. We also discuss the challenges and future directions of whole genome sequencing in aquaculture.


July 7, 2019

A gapless genome sequence of the fungus Botrytis cinerea.

Following earlier incomplete and fragmented versions of a genome sequence for the grey mould Botrytis cinerea, we here report a gapless, near-finished genome sequence for B. cinerea strain B05.10. The assembly comprises 18 chromosomes and was confirmed by an optical map and a genetic map based on ~75 000 SNP markers. All chromosomes contain fully assembled centromeric regions, and 10 chromosomes have telomeres on both ends. The genetic map consisted of 4153 cM and comparison of genetic distances with the physical distances identified 40 recombination hotspots. The linkage map also identified two mutations, located in the previously described genes Bos1 and BcsdhB, that confer resistance to the fungicides boscalid and iprodione. The genome was predicted to encode 11 701 proteins. RNAseq data from >20 different samples were used to validate and improve gene models. Manual curation of chromosome 1 revealed interesting features, such as the occurrence of a dicistronic transcript and fully overlapping genes in opposite orientations, as well as many spliced antisense transcripts. Manual curation also revealed that UTRs of genes can be complex and long, with many UTRs exceeding lengths of 1 kb and possessing multiple introns. Community annotation is in progress. This article is protected by copyright. All rights reserved. © 2016 BSPP AND JOHN WILEY & SONS LTD.


July 7, 2019

What distinguishes cyanobacteria able to revive after desiccation from those that cannot: the genome aspect.

Filamentous cyanobacteria are the main founders and primary producers in biological desert soil crusts (BSCs) and are likely equipped to cope with one of the harshest environmental conditions on earth including daily hydration/dehydration cycles, high irradiance and extreme temperatures. Here, we resolved and report on the genome sequence of Leptolyngbya ohadii, an important constituent of the BSC. Comparative genomics identified a set of genes present in desiccation-tolerant but not in dehydration-sensitive cyanobacteria. RT qPCR analyses showed that the transcript abundance of many of them is upregulated during desiccation in L. ohadii. In addition, we identified genes where the orthologs detected in desiccation-tolerant cyanobacteria differs substantially from that found in desiccation-sensitive cells. We present two examples, treS and fbpA (encoding trehalose synthase and fructose 1,6-bisphosphate aldolase respectively) where, in addition to the orthologs present in the desiccation-sensitive strains, the resistant cyanobacteria also possess genes with different predicted structures. We show that in both cases the two orthologs are transcribed during controlled dehydration of L. ohadii and discuss the genetic basis for the acclimation of cyanobacteria to the desiccation conditions in desert BSC.© 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.


July 7, 2019

Genomic analysis of 495 vancomycin-resistant Enterococcus faecium reveals broad dissemination of a vanA plasmid in more than 19 clones from Copenhagen, Denmark.

From 2012 to 2014, there has been a huge increase in vancomycin-resistant (vanA) Enterococcus faecium (VREfm) in Copenhagen, Denmark, with 602 patients infected or colonized with VREfm in 2014 compared with just 22 in 2012. The objective of this study was to describe the genetic epidemiology of VREfm to assess the contribution of clonal spread and horizontal transfer of the vanA transposon (Tn1546) and plasmid in the dissemination of VREfm in hospitals.VREfm from Copenhagen, Denmark (2012-14) were whole-genome sequenced. The clonal structure was determined and the structure of Tn1546-like transposons was characterized. One VREfm isolate belonging to the largest clonal group was sequenced using long-read technology to close a 37 kb vanA plasmid.Phylogeny revealed a polyclonal structure where 495 VREfm isolates were divided into 13 main groups and 7 small groups. The majority of the isolates were located in three groups (n?=?44, 100 and 218) and clonal spread of VREfm between wards and hospitals was identified. Five Tn1546-like transposon types were identified. A dominant truncated transposon (type 4, 92%) was spread across all but one VREfm group. The closed vanA plasmid was highly covered by reads from isolates containing the type 4 transposon.This study suggests that it was the dissemination of the type 4 Tn1546-like transposon and plasmid via horizontal transfer to multiple populations of E. faecium, followed by clonal spread of new VREfm clones, that contributed to the increase in and diversity of VREfm in Danish hospitals.© 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.


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.