Personne :
Charette, Steve

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Université Laval. Département de biochimie, de microbiologie et de bio-informatique
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Voici les éléments 1 - 10 sur 23
  • Publication
    Accès 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.
  • Publication
    Accès 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.
  • Publication
    Accès libre
    Various dictyostelids from the environment can produce multilamellar bodies
    (Ottawa National Research Council, 2020-07-31) Durocher, Alicia; Gagné-Thivierge, Cynthia; Charette, Steve
    Multilamellar bodies (MLBs), structures composed of concentric membrane layers, are known to be produced by different protozoa, including species of ciliates, free-living amoebae, and Dictyostelium discoideum social amoebae. Initially believed to be metabolic waste, potential roles like cell communication and food storage have been suggested for D. discoideum MLBs, which could be useful for the multicellular development of social amoebae and as a food source. However, among dictyostelids, this phenomenon has only been observed with D. discoideum, and mainly with laboratory strains grown in axenic conditions. It was thought that other social amoebae may also produce MLBs. Four environmental social amoeba isolates were characterized. All strains belong to the Dictyostelium genus, including some likely to be Dictyostelium giganteum. They have distinctive phenotypes comprising their growth rate on Klebsiella aerogenes lawns and the morphology of their fruiting bodies. They all produce MLBs like those produced by a D. discoideum laboratory strain when grown on K. aerogenes lawns, as revealed by analysis using the H36 antibody in epifluorescence microscopy as well as by transmission electron microscopy. Consequently, this study shows that MLBs are produced by various dictyostelid species, which further supports a role for MLBs in the lifestyle of amoebae.
  • Publication
    Accès libre
    Investigation of the virulence and genomics of Aeromonas salmonicida strains isolated from human patients
    (Elsevier, 2018-11-28) Vincent, Antony; Fernández-Bravo, Ana; Charette, Steve; Sanchis, Marta; Mayayo, Emilio; Figueras, M. J.
    The bacterium Aeromonas salmonicida is known since long time as a major fish pathogen unable to grow at 37 °C. However, some cases of human infection by putative mesophilic A. salmonicida have been reported. The goal of the present study is to examine two clinical cases of human infection by A. salmonicida in Spain and to investigate the pathogenicity in mammals of selected mesophilic A. salmonicida strains. An evaluation of the pathogenicity in a mouse model of clinical and environmental A. salmonicida strains was performed. The genomes of the strains were sequenced and analyzed in order to find the virulence determinants of these strains. The experimental infection in mice showed a gradient in the virulence of these strains and that some of them can cause necrotizing fasciitis and tissue damage in the liver. In addition to demonstrating significant genomic diversity among the strains studied, bioinformatics analyses permitted also to shed light on crucial elements for the virulence of the strains, like the presence of a type III secretion system in the one that caused the highest mortality in the experimental infection. Clinicians and microbiologists should consider these results for the inclusion of A. salmonicida in diagnosis tests since it is now clear that some mesophilic strains are also pathogens for humans.
  • Publication
    Haloacetic acid degradation by a biofilm in a simulated drinking water distribution system
    (IWA Publishing, 2013-03-01) Duchaine, Caroline; Sérodes, Jean-Baptiste; Pluchon, Cécile; Rodriguez, Manuel J.; Fournier-Larente, Jade; Berthiaume, C.; Gilbert, Yan.; Fillion, G.; Charette, Steve
    Haloacetic acids (HAAs) are disinfection by-products formed as a result of the reaction between chlorine and natural organic matter found in water. HAA concentrations have been observed to decrease at distribution system extremities. This decrease is associated with microbiological degradation by pipe wall biofilm. The objective of this study was to evaluate HAA degradation in a drinking water system in the presence of a biofilm and to identify the factors that influence this degradation. Degradation of dichloracetic acid (DCAA) and trichloroacetic acid (TCAA) was observed in a simulated distribution system. The results obtained showed that different parameters came into play simultaneously in the degradation of HAAs, including retention time, water temperature, biomass, composition of organic matter, and pipe diameter. Seasonal variations had a major effect on HAA degradation and biomass quantity was lower by 1 to 2 logs in the winter and spring compared with the fall. HAA removal decreased with increasingly large pipe diameters. The specific effects of each of these factors were difficult to isolate from each other owing to interactions.
  • Publication
    Accès libre
    Identification of dichloroacetic acid degrading Cupriavidus bacteria in a drinking water distribution network model
    (Blackwell Science, 2013-10-17) Duchaine, Caroline; Sérodes, Jean-Baptiste; Jubinville, Éric; Rodriguez, Manuel J.; Fournier-Larente, Jade; Berthiaume, C.; Gilbert, Yan.; Fillion, G.; Charette, Steve; Pluchon, Cécile
    Aims Bacterial community structure and composition of a drinking water network were assessed to better understand this ecosystem in relation to haloacetic acid (HAA) degradation and to identify new bacterial species having HAA degradation capacities. Methods and Results Biofilm samples were collected from a model system, simulating the end of the drinking water distribution network and supplied with different concentrations of dichloroacetic and trichloroacetic acids at different periods over the course of a year. The samples were analysed by culturing, denaturing gradient gel electrophoresis (DGGE) and sequencing. Pipe diameter and HAA ratios did not impact the bacterial community profiles, but the season had a clear influence. Based on DGGE profiles, it appeared that a particular biomass has developed during the summer compared with the other seasons. Among the bacteria isolated in this study, those from genus Cupriavidus were able to degrade dichloroacetic acid. Moreover, these bacteria degrade dichloroacetic acid at 18°C but not at 10°C. Conclusions The microbial diversity evolved throughout the experiment, but the bacterial community was distinct during the summer. Results obtained on the capacity of Cupriavidus to degrade DCAA only at 18°C but not at 10°C indicate that water temperature is a major element affecting DCAA degradation and confirming observations made regarding season influence on HAA degradation in the drinking water distribution network. Significance and Impact of the Study This is the first demonstration of the HAA biodegradation capacity of the genus Cupriavidus.
  • Publication
    Accès 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.
  • Publication
    Accès libre
    Beyond the A-layer : adsorption of lipopolysaccharides and characterization of bacteriophage-insensitive mutants of Aeromonas salmonicida subsp. salmonicida
    (Blackwell Science, 2019-05-22) Paquet, Valérie; Moineau, Sylvain; Vincent, Antony; Charette, Steve
    Aeromonas salmonicida subsp. salmonicida is a fish pathogen that causes furunculosis. Antibiotherapy used to treat furunculosis in fish has led to resistance. Virulent phages are increasingly seen as alternatives or complementary treatments against furunculosis in aquaculture environments. For phage therapy to be successful, it is essential to study the natural mechanisms of phage resistance in A. salmonicida subsp. salmonicida. Here, we generated bacteriophage‐insensitive mutants (BIMs) of A. salmonicida subsp. salmonicida, using a myophage with broad host range and characterized them. Phage plaques were different depending on whether the A‐layer surface array protein was expressed or not. The genome analysis of the BIMs helped to identify mutations in genes involved in the biogenesis of lipopolysaccharides (LPS) and on an uncharacterized gene (ASA_1998). The characterization of the LPS profile and gene complementation assays identified LPS as a phage receptor and confirmed the involvement of the uncharacterized protein ASA_1998 in phage infection. In addition, we confirmed that the presence of an A‐layer at the bacterial surface could act as protection against phages. This study brings new elements into our understanding of the phage adsorption to A. salmonicida subsp. salmonicida cells.
  • Publication
    Accès libre
    Unexpected diversity in the mobilome of a Pseudomonas aeruginosa strain isolated from a dental unit waterline revealed by SMRT Sequencing
    (Canadian Science Publishing, 2018-03-16) Barbeau, Jean; Vincent, Antony; Charette, Steve
    The Gram-negative bacterium Pseudomonas aeruginosa is found in several habitats, both natural and human-made, and is particularly known for its recurrent presence as a pathogen in the lungs of patients suffering from cystic fibrosis, a genetic disease. Given its clinical importance, several major studies have investigated the genomic adaptation of P. aeruginosa in lungs and its transition as acute infections become chronic. However, our knowledge about the diversity and adaptation of the P. aeruginosa genome to non-clinical environments is still fragmentary, in part due to the lack of accurate reference genomes of strains from the numerous environments colonized by the bacterium. Here, we used PacBio long-read technology to sequence the genome of PPF-1, a strain of P. aeruginosa isolated from a dental unit waterline. Generating this closed genome was an opportunity to investigate genomic features that are difficult to accurately study in a draft genome (contigs state). It was possible to shed light on putative genomic islands, some shared with other reference genomes, new prophages, and the complete content of insertion sequences. In addition, four different group II introns were also found, including two characterized here and not listed in the specialized group II intron database.