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April 21, 2020

Complete genome sequence of Pseudoalteromonas sp. MEBiC 03485, isolated from deep-sea sediment

Pseudoalteromonas strains are widely distributed in the marine environment and most have attracted considerable interest owing to their ability to synthesize biologically active metabolites. In this study, we report and describe the genome sequence of Pseudoalteromonas sp. MEBiC 03485, isolated from the deep-sea sediment of Pacific Ocean at a depth of 2000?m. The complete genome consisted of three contigs with a total genome size of 4,167,407?bp and a GC content of 40.76?l%, and was predicted to contain 4194 protein-coding genes and 131 non-coding RNA genes. The strain MEBiC 03485 genome was also shown to contain genes for diverse metabolic pathways. Genome analysis revealed that the genome of strain MEBiC 03485 was enriched with genes involved in signal transduction, mobile elements, and cold-adaptation, some of which might improve ecological fitness in the deep-sea environment. These findings improve our understanding of microbial adaptation strategies in deep-sea environments.

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April 21, 2020

Graph analysis of fragmented long-read bacterial genome assemblies.

Long-read genome assembly tools are expected to reconstruct bacterial genomes nearly perfectly, however they still produce fragmented assemblies in some cases. It would be beneficial to understand whether these cases are intrinsically impossible to resolve, or if assemblers are at fault, implying that genomes could be refined or even finished with little to no additional experimental cost.We propose a set of computational techniques to assist inspection of fragmented bacterial genome assemblies, through careful analysis of assembly graphs. By finding paths of overlapping raw reads between pairs of contigs, we recover potential short-range connections between contigs that were lost during the assembly process. We show that our procedure recovers 45% of missing contig adjacencies in fragmented Canu assemblies, on samples from the NCTC bacterial sequencing project. We also observe that a simple procedure based on enumerating weighted Hamiltonian cycles can suggest likely contig orderings. In our tests, the correct contig order is ranked first in half of the cases and within the top-3 predictions in nearly all evaluated cases, providing a direction for finishing fragmented long-read assemblies.https://gitlab.inria.fr/pmarijon/knot.Supplementary data are available at Bioinformatics online. © The Author(s) (2019). Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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April 21, 2020

A comprehensive evaluation of long read error correction methods

Motivation: Third-generation sequencing technologies can sequence long reads, which is advancing the frontiers of genomics research. However, their high error rates prohibit accurate and efficient downstream analysis. This difficulty has motivated the development of many long read error correction tools, which tackle this problem through sampling redundancy and/or leveraging accurate short reads of the same biological samples. Existing studies to asses these tools use simulated data sets, and are not sufficiently comprehensive in the range of software covered or diversity of evaluation measures used. Results: In this paper, we present a categorization and review of long read error correction methods, and provide a comprehensive evaluation of the corresponding long read error correction tools. Leveraging recent real sequencing data, we establish benchmark data sets and set up evaluation criteria for a comparative assessment which includes quality of error correction as well as run-time and memory usage. We study how trimming and long read sequencing depth affect error correction in terms of length distribution and genome coverage post-correction, and the impact of error correction performance on an important application of long reads, genome assembly. We provide guidelines for practitioners for choosing among the available error correction tools and identify directions for future research.

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April 21, 2020

Morphological and genomic characterisation of the hybrid schistosome infecting humans in Europe reveals a complex admixture between Schistosoma haematobium and Schistosoma bovis parasites

Schistosomes cause schistosomiasis, the worldtextquoterights second most important parasitic disease after malaria. A peculiar feature of schistosomes is their ability to produce viable and fertile hybrids. Originally only present in the tropics, schistosomiasis is now also endemic in Europe. Based on two genetic markers the European species had been identified as a hybrid between the ruminant-infective Schistosoma bovis and the human-infective Schistosoma haematobium.Here we describe for the first time the genomic composition of the European schistosome hybrid (77% of S. haematobium and 23% of S. bovis origins), its morphometric parameters and its compatibility with the European vector snail and intermediate host Compatibility is a key parameter for the parasites life cycle progression. We also show that egg morphology (a classical diagnostic parameter) does not allow for differential diagnosis while genetic tests do so. Additionally, we performed genome assembly improvement and annotation of S. bovis, the parental species for which no satisfactory genome assembly was available.For the first time since the discovery of hybrid schistosomes, these results reveal at the whole genomic level a complex admixture of parental genomes highlighting (i) the high permeability of schistosomes to other speciestextquoteright alleles, and (ii) the importance of hybrid formation for pushing species boundaries not only conceptionally but also geographically.

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April 21, 2020

Genome sequence analysis of 91 Salmonella Enteritidis isolates from mice caught on poultry farms in the mid 1990s.

A total of 91 draft genome sequences were used to analyze isolates of Salmonella enterica serovar Enteritidis obtained from feral mice caught on poultry farms in Pennsylvania. One objective was to find mutations disrupting open reading frames (ORFs) and another was to determine if ORF-disruptive mutations were present in isolates obtained from other sources. A total of 83 mice were obtained between 1995-1998. Isolates separated into two genomic clades and 12 subgroups due to 742 mutations. Nineteen ORF-disruptive mutations were found, and in addition, bigA had exceptional heterogeneity requiring additional evaluation. The TRAMS algorithm detected only 6 ORF disruptions. The sefD mutation was the most frequently encountered mutation and it was prevalent in human, poultry, environmental and mouse isolates. These results confirm previous assessments of the mouse as a rich source of Salmonella enterica serovar Enteritidis that varies in genotype and phenotype. Copyright © 2019. Published by Elsevier Inc.

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April 21, 2020

A microbial factory for defensive kahalalides in a tripartite marine symbiosis.

Chemical defense against predators is widespread in natural ecosystems. Occasionally, taxonomically distant organisms share the same defense chemical. Here, we describe an unusual tripartite marine symbiosis, in which an intracellular bacterial symbiont (“Candidatus Endobryopsis kahalalidefaciens”) uses a diverse array of biosynthetic enzymes to convert simple substrates into a library of complex molecules (the kahalalides) for chemical defense of the host, the alga Bryopsis sp., against predation. The kahalalides are subsequently hijacked by a third partner, the herbivorous mollusk Elysia rufescens, and employed similarly for defense. “Ca E. kahalalidefaciens” has lost many essential traits for free living and acts as a factory for kahalalide production. This interaction between a bacterium, an alga, and an animal highlights the importance of chemical defense in the evolution of complex symbioses.Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

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April 21, 2020

Rapid transcriptional responses to serum exposure are associated with sensitivity and resistance to antibody-mediated complement killing in invasive Salmonella Typhimurium ST313

Background: Salmonella Typhimurium ST313 exhibits signatures of adaptation to invasive human infection, including higher resistance to humoral immune responses than gastrointestinal isolates. Full resistance to antibody-mediated complement killing (serum resistance) among nontyphoidal Salmonellae is uncommon, but selection of highly resistant strains could compromise vaccine-induced antibody immunity. Here, we address the hypothesis that serum resistance is due to a distinct genotype or transcriptome response in S. Typhimurium ST313.

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April 21, 2020

Complete Genome Sequence of a Parabacteroides distasonis Strain (CavFT hAR46) Isolated from a Gut Wall-Cavitating Microlesion in a Patient with Severe Crohn’s Disease.

Crohn’s disease (CD) is a chronic inflammatory bowel disease (IBD) of the digestive tract in humans. There is evidence that Parabacteroides distasonis could contribute to IBD. Here, we present the complete genome sequence of a strain designated CavFT-hAR46, which was isolated from a gut intramural cavernous fistulous tract (CavFT) microlesion in a CD patient.Copyright © 2019 Yang et al.

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April 21, 2020

Complete Genome Sequence of Subcluster 5.2 Synechococcus sp. Strain CB0101, Isolated from the Chesapeake Bay.

Synechococcus sp. strain CB0101 is a model strain for cyanobacteria living in the estuarine environment. It is also a representative member of marine Synechococcus subcluster 5.2. The draft genome sequence of CB0101 was reported in 2014 with 454 sequencing. Here, we report the complete genome sequence of CB0101, obtained with PacBio sequencing. CB0101 contains a specialized array of genes which are involved in sensing, responding to, and persisting in the presence of environmental stress.Copyright © 2019 Fucich et al.

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April 21, 2020

Complete Genome Sequence of Streptomyces sp. Strain SGAir0924, an Actinobacterium Isolated from Outdoor Air in Singapore.

Streptomyces sp. strain SGAir0924 was isolated from outdoor air collected in Singapore. Its genome was assembled using long reads generated by single-molecule real-time sequencing. The final assembly had one chromosome of 7.65?Mb and three plasmids with an average length of 142 kb. The genome contained 6,825 protein-coding genes, 68 tRNAs, and 18 rRNAs.Copyright © 2019 Gupta et al.

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April 21, 2020

Complete Genome Sequence of Dehalococcoides mccartyi Strain FL2, a Trichloroethene-Respiring Anaerobe Isolated from Pristine Freshwater Sediment.

Dehalococcoides mccartyi strain FL2 couples growth to hydrogen oxidation and reductive dechlorination of trichloroethene and cis- and trans-1,2-dichloroethenes. Strain FL2 has a 1.42-Mb genome with a G+C content of 47.0% and carries 1,465 protein-coding sequences, including 24 reductive dehalogenase genes.Copyright © 2019 Yan et al.

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