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Charette, Steve

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Charette

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Université Laval. Département de biochimie, de microbiologie et de bio-informatique

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  • PublicationAccès libre
    Characterization and diversity of phages infecting Aeromonas salmonicida subsp. salmonicida
    (Nature Publishing Group, 2017-08-01) Tremblay, Denise; Paquet, Valérie; Bernatchez, Alex; Moineau, Sylvain; Vincent, Antony; Charette, Steve
    Phages infecting Aeromonas salmonicida subsp. salmonicida, the causative agent of the fish disease furunculosis, have been isolated for decades but very few of them have been characterized. Here, the host range of 12 virulent phages, including three isolated in the present study, was evaluated against a panel of 65 A. salmonicida isolates, including representatives of the psychrophilic subspecies salmonicida, smithia, masoucida, and the mesophilic subspecies pectinolytica. This bacterial set also included three isolates from India suspected of being members of a new subspecies. Our results allowed to elucidate a lytic dichotomy based on the lifestyle of A. salmonicida (mesophilic or psychrophilic) and more generally, on phage types (lysotypes) for the subspecies salmonicida. The genomic analyses of the 12 phages from this study with those available in GenBank led us to propose an A. salmonicida phage pan-virome. Our comparative genomic analyses also suggest that some phage genes were under positive selection and A. salmonicida phage genomes having a discrepancy in GC% compared to the host genome encode tRNA genes to likely overpass the bias in codon usage. Finally, we propose a new classification scheme for A. salmonicida phages.
  • PublicationAccès libre
    Implementing a web-based introductory bioinformatics course for non-bioinformaticians that incorporates practical exercises
    (Elsevier Science, 2017-09-13) Bourbonnais, Yves; Droit, Arnaud; Deveau, Hélène; Lagüe, Patrick; Brouard, Jean-Simon.; Lemieux, Claude; Guertin, Michel; Gagné, Stéphane; Vincent, Antony; Rathier, Louis; Charette, Steve
    A recent scientific discipline, bioinformatics, defined as using informatics for the study of biological problems, is now a requirement for the study of biological sciences. Bioinformatics has become such a powerful and popular discipline that several academic institutions have created programs in this field, allowing students to become specialized. However, biology students who are not involved in a bioinformatics program also need a solid toolbox of bioinformatics software and skills. Therefore, we have developed a completely online bioinformatics course for non-bioinformaticians, entitled “BIF-1901 Introduction à la bio-informatique et à ses outils (Introduction to bioinformatics and bioinformatics tools),” given by the Department of Biochemistry, Microbiology, and Bioinformatics of Université Laval (Quebec City, Canada). This course requires neither a bioinformatics background nor specific skills in informatics. The underlying main goal was to produce a completely online up-to-date bioinformatics course, including practical exercises, with an intuitive pedagogical framework. The course, BIF-1901, was conceived to cover the three fundamental aspects of bioinformatics: (1) informatics, (2) biological sequence analysis, and (3) structural bioinformatics. This article discusses the content of the modules, the evaluations, the pedagogical framework, and the challenges inherent to a multidisciplinary, fully online course. © 2017 by The International Union of Biochemistry and Molecular Biology, 2017.
  • PublicationAccès libre
    Study of mesophilic Aeromonas salmonicida A527 strain sheds light on the species’ lifestyles and taxonomic dilemma
    (Elsevier/North-Holland, 2017-11-08) Moineau, Sylvain; Rouleau, Francois D.; Vincent, Antony; Charette, Steve
    The Gram-negative bacterium Aeromonas salmonicida contains five subspecies: salmonicida, smithia, achromogenes, masoucida and pectinolytica. Pectinolytica is a mesophilic subspecies with the ability to thrive at a wide range of temperatures, including 37°C, while the four other subspecies are psychrophilic, restricted to lower temperatures. The psychrophilic subspecies are known to infect a wide range of fishes. However, there is no evidence of pathogenicity for the mesophilic subspecies pectinolytica. Study of the differences between the mesophilic and psychrophilic subspecies is hampered by the lack of completely sequenced and closed genomes from the mesophilic subspecies. A previous study reported that insertion sequences, which can induce genomic rearrangements at temperatures around 25°C, could be one of the determinants explaining the differences in lifestyle (mesophilic or psychrophilic) between the subspecies. In this study, the genome of mesophilic strain A527 of A. salmonicida was sequenced, closed and analyzed to investigate the mesophilic–psychrophilic discrepancy. This reference genome supports the hypothesis that insertion sequences are major determinants of the lifestyle differences between the A. salmonicida subspecies. Moreover, the phylogenetic analysis performed to position strain A527 within the taxonomy raises an issue regarding the intraspecies structure of A. salmonicida.
  • PublicationAccès libre
    Next-generation sequencing (NGS) in the microbiological world : how to make the most of your money
    (Elsevier, 2016-06-16) Culley, Alexander; Vincent, Antony; Boyle, Brian; Charette, Steve; Derome, Nicolas
    The Sanger sequencing method produces relatively long DNA sequences of unmatched quality and has been considered for long time as the gold standard for sequencing DNA. Many improvements of the Sanger method that culminated with fluorescent dyes coupled with automated capillary electrophoresis enabled the sequencing of the first genomes. Nevertheless, using this technology to sequence whole genomes was costly, laborious and time consuming even for genomes that are relatively small in size. A major technological advance was the introduction of next-generation sequencing (NGS) pioneered by 454 Life Sciences in the early part of the 21th century. NGS allowed scientists to sequence thousands to millions of DNA molecules in a single machine run. Since then, new NGS technologies have emerged and existing NGS platforms have been improved, enabling the production of genome sequences at an unprecedented rate as well as broadening the spectrum of NGS applications. The current affordability of generating genomic information, especially with microbial samples, has resulted in a false sense of simplicity that belies the fact that many researchers still consider these technologies a black box. In this review, our objective is to identify and discuss four steps that we consider crucial to the success of any NGS-related project. These steps are: (1) the definition of the research objectives beyond sequencing and appropriate experimental planning, (2) library preparation, (3) sequencing and (4) data analysis. The goal of this review is to give an overview of the process, from sample to analysis, and discuss how to optimize your resources to achieve the most from your NGS-based research. Regardless of the evolution and improvement of the sequencing technologies, these four steps will remain relevant.
  • PublicationAccès libre
    Microbe Profile: Aeromonas salmonicida: an opportunistic pathogen with multiple personalities
    (Microbiology Society, 2021-05-04) Charette, Steve
    The bacterial species Aeromonas salmonicida is a fish pathogen. Feared by fish farmers everywhere on Earth over the past century, this species has turned out to be more diverse than initially suspected. While some psychrophilic subspecies cannot grow at temperatures above 25 °C or 30 °C, other mesophilic strains growing up to 37 °C and above are now characterized. Adding to the surprising diversity of this species, some of the mesophilic strains infect mammals and birds. The remarkable diversity is explained in part by the presence of numerous mobile genetic elements, which sculpt and modify the genome of the various strains of this species.
  • PublicationAccès libre
    Characterization of bacteriophage T7-Ah reveals its lytic activity against a subset of both mesophilic and psychrophilic Aeromonas salmonicida strains
    (Springer, 2021-01-04) Leduc, Gabrielle R.; Paquet, Valérie; Vincent, Antony; Charette, Steve
    Aeromonas salmonicida strains cause problematic bacterial infections in the aquaculture industry worldwide. The genus Aeromonas includes both mesophilic and psychrophilic species. Bacteriophages that infect Aeromonas spp. strains are usually specific for mesophilic or psychrophilic species; only a few bacteriophages can infect both types of strains. In this study, we characterized the podophage T7-Ah, which was initially found to infect the Aeromonas salmonicida HER1209 strain. The burst size of T7-Ah against its original host is 72 new virions per infected cell, and its burst time is 30 minutes. It has been found that this phage can lyse both mesophilic and psychrophilic A. salmonicida strains, as well as one strain of Escherichia coli. Its genome comprises 40,153 bp of DNA and does not contain any recognizable toxin or antibiotic resistance genes. The adsorption rate of the phage on highly sensitive bacterial strains was variable and could not be related to the presence or absence of a functional A-layer on the surface of the bacterial strains. The lipopolysaccharide migration patterns of both resistant and sensitive bacterial strains were also studied and compared to investigate the nature of the potential receptor of this phage on the bacterial surface. This study sheds light on the surprising diversity of lifestyles of the bacterial strains sensitive to phage T7-Ah and opens the door to the potential use of this phage against A. salmonicida infections in aquaculture.
  • PublicationAccès libre
    One Aeromonas salmonicida subsp. salmonicida isolate with a pAsa5 variant bearing antibiotic resistance and a pRAS3 variant making a link with a swine pathogen
    (Amsterdam Elsevier, 2019-11-10) Schneider, Anna; Frenette, Michel; Paquet, Valérie; Charette, Steve.; Massicotte, Marie-Ange; Vincent, Antony
    The Gram-negative bacterium Aeromonas salmonicida subsp. salmonicida is an aquatic pathogen which causes furunculosis to salmonids, especially in fish farms. The emergence of strains of this bacterium exhibiting antibiotic resistance is increasing, limiting the effectiveness of antibiotherapy as a treatment against this worldwide disease. In the present study, we discovered an isolate of A. salmonicida subsp. salmonicida that harbors two novel plasmids variants carrying antibiotic resistance genes. The use of long-read sequencing (PacBio) allowed us to fully characterize those variants, named pAsa5-3432 and pRAS3-3432, which both differ from their classic counterpart through their content in mobile genetic elements. The plasmid pAsa5-3432 carries a new multidrug region composed of multiple mobile genetic elements, including a Class 1 integron similar to an integrated element of Salmonella enterica. With this new region, probably acquired through plasmid recombination, pAsa5-3432 is the first reported plasmid of this bacterium that bears both an essential virulence factor (the type three secretion system) and multiple antibiotic resistance genes. As for pRAS3-3432, compared to the classic pRAS3, it carries a new mobile element that has only been identified in Chlamydia suis. Hence, with the identification of those two novel plasmids harboring mobile genetic elements that are normally encountered in other bacterial species, the present study puts emphasis on the important impact of mobile genetic elements in the genomic plasticity of A. salmonicida subsp. salmonicida and suggests that this aquatic bacterium could be an important reservoir of antibiotic resistance genes that can be exchanged with other bacteria, including human and animal pathogens.
  • PublicationAccès libre
    The fate of multilamellar bodies produced and secreted by Dictyostelium discoideum amoebae
    (Elsevier, 2017-10-14) Paquet, Valérie; Denoncourt, Alix; Charette, Steve; Durocher, Alicia
    The amoeba Dictyostelium discoideum produces and secretes multilamellar bodies (MLBs) mainly composed of amoebal membranes upon digestion of bacteria. After their secretion, the fate of these MLBs remains unknown. The aim of this study was to determine if protozoa can internalize and digest secreted D. discoideum MLBs. Our results showed that MLBs were ingested by naive axenic D. discoideum cells (i. e. cells not exposed to bacteria and consequently not producing MLBs). Only a small fraction of the ingested MLBs were found in cells’ post-lysosomes compared to undigestible beads suggesting that naive amoebae digest them. D. discoideum MLBs were also ingested by the ciliates Tetrahymena pyriformis and Tetrahymena thermophila. MLBs internalized by the ciliates were compacted into pellets and expelled in the extracellular medium without obvious signs of degradation. The results of this study provide new insights on the biological function of MLBs and, considering that MLBs are also involved in bacteria packaging, suggest additional layers of complexity in microbial interactions.
  • PublicationAccès libre
    Isolation of vB_AsaM_LPM4 reveals the dynamics of Prophage 3 in Aeromonas salmonicida subsp. salmonicida
    (Springer-Verlag, 2023-01-20) Leduc, Gabrielle R.; Paquet, Valérie; Vincent, Antony; Charette, Steve; Piché, Laurie C.
    Aeromonas salmonicida subsp. salmonicida causes furunculosis, a major infection that affects fish farms worldwide. We isolated phage vB_AsaM_LPM4 (LPM4) from a diseased fish. Based on its DNA sequence, LPM4 is identical to the uncharacterized Prophage 3, a prophage present mostly in North American A. salmonicida subsp. salmonicida isolates that bear the genomic island AsaGEI2a. Prophage 3 and AsaGEI2a are inserted side by side in the bacterial chromosome. The LPM4/Prophage 3 sequence is similar to that of other prophages found in various members of the genus Aeromonas. LPM4 specifically infects A. salmonicida subsp. salmonicida strains that do not already bear Prophage 3. The presence of an A-layer on the surface of the bacteria is not necessary for the adsorption of phage LPM4 but seems to facilitate its infection process. We also successfully produced lysogenic strains that bear Prophage 3 using sensitive strains with different genetic backgrounds, suggesting that there is no interdependency between LPM4 and AsaGEIs. PCR analysis of the excision dynamics of Prophage 3 and AsaGEIs revealed that these genetic elements can spontaneously excise themselves from the bacterial chromosome independently of one another. Through the isolation and characterization of LPM4, this study reveals new facets of Prophage 3 and AsaGEIs
  • PublicationAccès libre
    Genomic and phenotypic characterization of an atypical Aeromonas salmonicida strain isolated from a lumpfish and producing unusual granular structures
    (Oxford Blackwell Science, 2018-01-09) Rouleau, Francois D.; Vincent, Antony; Charette, Steve
    Aeromonas salmonicida strains are roughly classified into two categories, typical and atypical strains. The latter mainly regroup isolates that present unusual phenotypes or hosts, comparatively to the typical strains that belong to the salmonicida subspecies. This study focuses on an uncharacterized atypical strain, M18076-11, isolated from lumpfish (Cyclopterus lumpus) and not part of the four recognized Aeromonas salmonicida subspecies. This isolate presents an unreported phenotype in the A. salmonicida species: the formation of large granular aggregates. Granules are formed of a heterogeneous mix of live and dead cells, with live cells composing the majority of the population. Even if no mechanism was determined to cause cellular aggregation, small globular structures at the cell surface were observed, which might affect granular formation. Pan-genome phylogenetic analysis indicated that this strain groups alongside the masoucida subspecies. However, phenotypic tests showed that these strains have diverging phenotypes, suggesting that M18076-11 might belong to a new subspecies. Also, a pAsal1-like plasmid, which was only reported in strains of the subspecies salmonicida, was discovered in M18076-11. This study sheds light on unsuspected diversity in A. salmonicida subspecies and stresses the need of thorough identification when a new strain is encountered, as unique traits might be discovered.