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July 7, 2019  |  

Complex population structure and virulence differences among serotype 2 Streptococcus suis strains belonging to sequence type 28.

Streptococcus suis is a major swine pathogen and a zoonotic agent. Serotype 2 strains are the most frequently associated with disease. However, not all serotype 2 lineages are considered virulent. Indeed, sequence type (ST) 28 serotype 2 S. suis strains have been described as a homogeneous group of low virulence. However, ST28 strains are often isolated from diseased swine in some countries, and at least four human ST28 cases have been reported. Here, we used whole-genome sequencing and animal infection models to test the hypothesis that the ST28 lineage comprises strains of different genetic backgrounds and different virulence. We used 50 S. suis ST28 strains isolated in Canada, the United States and Japan from diseased pigs, and one ST28 strain from a human case isolated in Thailand. We report a complex population structure among the 51 ST28 strains. Diversity resulted from variable gene content, recombination events and numerous genome-wide polymorphisms not attributable to recombination. Phylogenetic analysis using core genome single-nucleotide polymorphisms revealed four discrete clades with strong geographic structure, and a fifth clade formed by US, Thai and Japanese strains. When tested in experimental animal models, strains from this latter clade were significantly more virulent than a Canadian ST28 reference strain, and a closely related Canadian strain. Our results highlight the limitations of MLST for both phylogenetic analysis and virulence prediction and raise concerns about the possible emergence of ST28 strains in human clinical cases.

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July 7, 2019  |  

Complete genome and plasmid sequences of three Canadian strains of Salmonella enterica subsp. enterica serovar Enteritidis belonging to phage types 8, 13, and 13a.

Salmonella enterica subsp. enterica serovar Enteritidis is a prominent cause of human salmonellosis frequently linked to poultry products. In Canada, S. Enteritidis phage types 8, 13, and 13a predominate among both clinical and poultry isolates. Here, we report the complete genome and plasmid sequences of poultry isolates of these three phage types. Copyright © 2015 Rehman et al.

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July 7, 2019  |  

Improved draft genome sequence of Clostridium pasteurianum strain ATCC 6013 (DSM 525) using a hybrid next-generation sequencing approach.

We present an improved draft genome sequence for Clostridium pasteurianum strain ATCC 6013 (DSM 525), the type strain of the species and an important solventogenic bacterium with industrial potential. Availability of a near-complete genome sequence will enable strain engineering of this promising bacterium. Copyright © 2014 Pyne et al.

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July 7, 2019  |  

First complete genome sequence of Staphylococcus xylosus, a meat starter culture and a host to propagate Staphylococcus aureus phages.

Staphylococcus xylosus is a bacterial species used in meat fermentation and a commensal microorganism found on animals. We present the first complete circular genome from this species. The genome is composed of 2,757,557 bp, with a G+C content of 32.9%, and contains 2,514 genes and 79 structural RNAs. Copyright © 2014 Labrie et al.

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July 7, 2019  |  

High resolution assembly and characterization of genomes of Canadian isolates of Salmonella Enteritidis.

There is a need to characterize genomes of the foodborne pathogen, Salmonella enterica serovar Enteritidis (SE) and identify genetic information that could be ultimately deployed for differentiating strains of the organism, a need that is yet to be addressed mainly because of the high degree of clonality of the organism. In an effort to achieve the first characterization of the genomes of SE of Canadian origin, we carried out massively parallel sequencing of the nucleotide sequence of 11 SE isolates obtained from poultry production environments (n?=?9), a clam and a chicken, assembled finished genomes and investigated diversity of the SE genome.The median genome size was 4,678,683 bp. A total of 4,833 chromosomal genes defined the pan genome of our field SE isolates consisting of 4,600 genes present in all the genomes, i.e., core genome, and 233 genes absent in at least one genome (accessory genome). Genome diversity was demonstrable by the presence of 1,360 loci showing single nucleotide polymorphism (SNP) in the core genome which was used to portray the genetic distances by means of a phylogenetic tree for the SE isolates. The accessory genome consisted mostly of previously identified SE prophage sequences as well as two, apparently full-sized, novel prophages namely a 28 kb sequence provisionally designated as SE-OLF-10058 (3) prophage and a 43 kb sequence provisionally designated as SE-OLF-10012 prophage.The number of SNPs identified in the relatively large core genome of SE is a reflection of substantial diversity that could be exploited for strain differentiation as shown by the development of an informative phylogenetic tree. Prophage sequences can also be exploited for SE strain differentiation and lineage tracking. This work has laid the ground work for further studies to develop a readily adoptable laboratory test for the subtyping of SE.

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July 7, 2019  |  

First complete genome sequence of Haemophilus influenzae serotype a.

Haemophilus influenzae is an important human pathogen that primarily infects small children. In recent years, H. influenzae serotype a has emerged as a significant cause of invasive disease among indigenous populations. Here, we present the first complete whole-genome sequence of H. influenzae serotype a.© Crown copyright 2017.

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July 7, 2019  |  

Multi-omics approach to study global changes in a triclosan-resistant mutant strain of Acinetobacter baumannii ATCC 17978.

Acinetobacter baumannii AB042, a triclosan-resistant mutant strain, was examined for modulated gene expression using whole-genome sequencing, transcriptomics and proteomics in order to understand the mechanism of triclosan resistance as well as its impact on A. baumannii. Data revealed modulated expression of the fatty acid metabolism pathway, co-factors known to play a role in the synthesis of fatty acids, as well as several transcriptional regulators. The membrane composition of the mutant revealed a decrease in C18 with a corresponding increase in C16 fatty acids compared with the parent strain A. baumannii ATCC 17978. These data indicate that A. baumannii responds to triclosan by altering the expression of genes involved in fatty acid metabolism, antibiotic resistance and amino acid metabolism. Copyright © 2016 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

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July 7, 2019  |  

An antimicrobial peptide-resistant minor subpopulation of Photorhabdus luminescens is responsible for virulence.

Some of the bacterial cells in isogenic populations behave differently from others. We describe here how a new type of phenotypic heterogeneity relating to resistance to cationic antimicrobial peptides (CAMPs) is determinant for the pathogenic infection process of the entomopathogenic bacterium Photorhabdus luminescens. We demonstrate that the resistant subpopulation, which accounts for only 0.5% of the wild-type population, causes septicemia in insects. Bacterial heterogeneity is driven by the PhoPQ two-component regulatory system and expression of pbgPE, an operon encoding proteins involved in lipopolysaccharide (LPS) modifications. We also report the characterization of a core regulon controlled by the DNA-binding PhoP protein, which governs virulence in P. luminescens. Comparative RNAseq analysis revealed an upregulation of marker genes for resistance, virulence and bacterial antagonism in the pre-existing resistant subpopulation, suggesting a greater ability to infect insect prey and to survive in cadavers. Finally, we suggest that the infection process of P. luminescens is based on a bet-hedging strategy to cope with the diverse environmental conditions experienced during the lifecycle.

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July 7, 2019  |  

An improved genome assembly uncovers prolific tandem repeats in Atlantic cod.

The first Atlantic cod (Gadus morhua) genome assembly published in 2011 was one of the early genome assemblies exclusively based on high-throughput 454 pyrosequencing. Since then, rapid advances in sequencing technologies have led to a multitude of assemblies generated for complex genomes, although many of these are of a fragmented nature with a significant fraction of bases in gaps. The development of long-read sequencing and improved software now enable the generation of more contiguous genome assemblies.By combining data from Illumina, 454 and the longer PacBio sequencing technologies, as well as integrating the results of multiple assembly programs, we have created a substantially improved version of the Atlantic cod genome assembly. The sequence contiguity of this assembly is increased fifty-fold and the proportion of gap-bases has been reduced fifteen-fold. Compared to other vertebrates, the assembly contains an unusual high density of tandem repeats (TRs). Indeed, retrospective analyses reveal that gaps in the first genome assembly were largely associated with these TRs. We show that 21% of the TRs across the assembly, 19% in the promoter regions and 12% in the coding sequences are heterozygous in the sequenced individual.The inclusion of PacBio reads combined with the use of multiple assembly programs drastically improved the Atlantic cod genome assembly by successfully resolving long TRs. The high frequency of heterozygous TRs within or in the vicinity of genes in the genome indicate a considerable standing genomic variation in Atlantic cod populations, which is likely of evolutionary importance.

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July 7, 2019  |  

Complete genome sequence and comparative genomics of the probiotic yeast Saccharomyces boulardii.

The probiotic yeast, Saccharomyces boulardii (Sb) is known to be effective against many gastrointestinal disorders and antibiotic-associated diarrhea. To understand molecular basis of probiotic-properties ascribed to Sb we determined the complete genomes of two strains of Sb i.e. Biocodex and unique28 and the draft genomes for three other Sb strains that are marketed as probiotics in India. We compared these genomes with 145 strains of S. cerevisiae (Sc) to understand genome-level similarities and differences between these yeasts. A distinctive feature of Sb from other Sc is absence of Ty elements Ty1, Ty3, Ty4 and associated LTR. However, we could identify complete Ty2 and Ty5 elements in Sb. The genes for hexose transporters HXT11 and HXT9, and asparagine-utilization are absent in all Sb strains. We find differences in repeat periods and copy numbers of repeats in flocculin genes that are likely related to the differential adhesion of Sb as compared to Sc. Core-proteome based taxonomy places Sb strains along with wine strains of Sc. We find the introgression of five genes from Z. bailii into the chromosome IV of Sb and wine strains of Sc. Intriguingly, genes involved in conferring known probiotic properties to Sb are conserved in most Sc strains.

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July 7, 2019  |  

Complete genome of a panresistant Pseudomonas aeruginosa strain, isolated from a patient with respiratory failure in a Canadian community hospital.

We report here the complete genome sequence of a panresistant Pseudomonas aeruginosa strain, isolated from a patient with respiratory failure in Canada. No carbapenemase genes were identified. Carbapenem resistance is attributable to a frameshift in the oprD gene; the basis for colistin resistance remains undetermined. Copyright © 2017 Xiong et al.

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July 7, 2019  |  

Complete genome sequences of 12 isolates of Listeria monocytogenes belonging to serotypes 1/2a, 1/2b, and 4b obtained from food products and food-processing environments in Canada.

Listeria monocytogenes is the etiological agent for an often fatal foodborne illness known as listeriosis. Here, we present the complete genome sequences of 12 L. monocytogenes isolates representing the three most common serotypes of this pathogen (1/2a, 1/2b, and 4b), collected in Canada from different food products and environmental sources.© Crown copyright 2017.

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July 7, 2019  |  

Biosynthesis of 1a-hydroxycorticosterone in the winter skate Leucoraja ocellata: evidence to suggest a novel steroidogenic route.

The present study explores the ability of intracellular bacteria within the renal-inter-renal tissue of the winter skate Leucoraja ocellata to metabolize steroids and contribute to the synthesis of the novel elasmobranch corticosteroid, 1a-hydroxycorticosterone (1a-OH-B). Despite the rarity of C1 hydroxylation noted in the original identification of 1a-OH-B, literature provides evidence for steroid C1 hydroxylation by micro-organisms. Eight ureolytic bacterial isolates were identified in the renal-inter-renal tissue of L. ocellata, the latter being the site of 1a-OH-B synthesis. From incubations of bacterial isolates with known amounts of potential 1a-OH-B precursors, one isolate UM008 of the genus Rhodococcus was seen to metabolize corticosteroids and produce novel products via HPLC analysis. Cations Zn2+and Fe3+altered metabolism of certain steroid precursors, suggesting inhibition of Rhodococcus steroid catabolism. Genome sequencing of UM008 identified strong sequence and structural homology to that of Rhodococcus erythropolis PR4. A complete enzymatic pathway for steroid-ring oxidation as documented within other Actinobacteria was identified within the UM008 genome. This study highlights the potential role of Rhodococcus bacteria in steroid metabolism and proposes a novel alternative pathway for 1a-OH-B synthesis, suggesting a unique form of mutualism between intracellular bacteria and their elasmobranch host.© 2017 The Fisheries Society of the British Isles.

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