Canadian journal of microbiology最新文献

Unprecedented seabird mass mortality events (MMEs) were reported in multiple European countries in 2022 and 2023. These events were attributed to Clade 2.3.4.4b H5N1 high pathogenicity avian influenza viruses (HPAIVs). In Denmark, populations of Sandwich Terns (Thalasseus sandvicensis) and Black-headed Gulls (Chroicocephalus ridibundus) were significantly impacted. Sandwich Tern mortality occurred primarily between May and June of 2022 and was caused by the HPAIV genotype EA-AB. From 2022 to 2023, Danish Sandwich Tern populations decreased by 36%. Sandwich Terns commonly nest within Black-headed Gull colonies, allowing for direct contact between the species. Despite their proximity, in 2022, neither adults nor chicks of Black-headed Gulls exhibited morbidity associated with HPAIV. During the autumn of 2022 and the winter 2022/23 a novel clade 2.3.4.4b H5N1 HPAIV, genotype EA-BB, emerged in Black-headed Gulls. The new genotype caused the death of at least 3000 adult Black-headed Gulls in Denmark (i.e., >1.8% of the Danish breeding population) in the spring of 2023. Notably, in 2023 Sandwich Tern chicks, but not adults, in contact with Black-headed Gulls were affected by mass mortality. These observations suggest that adult Terns in 2023 were less susceptible to HPAIV infection, mitigating the impact of MMEs.

Certain Shewanella spp. cause spoilage of seafood. However, Shewanella from fish production facilities in Canada have not yet been characterized. In our study, we first isolated Shewanella oncorhynchi S23-S33 (S2-3) from the water in a rainbow trout tank from a recirculating aquaculture system (RAS) facility located in Alberta, Canada. Later we found another strain (FD-1) from the biofilters from the same facility. Whole genome sequencing revealed that both strains possess gene clusters for the biosynthesis of eicosapentaenoic acid and we confirmed the production in FD-1 by gas chromatography. Phylogenetic analyses showed the close relatedness of FD-1 and S2-3 to S. oncorhynchi S-1. Rainbow trout filets inoculated with FD-1 turned brown in colour compared to uninoculated. However, when we inoculated retail pink salmon (Oncorhynchus gorbuscha) with either FD-1 or S2-3, we did not observe the brown colour change. The storage time had a significant (P < 0.0001) impact on the lightness (L^*), red/green (a^*), and yellow/blue (b^*) of pink salmon. In summary, our research note records the preliminary characterization of Shewanella from a RAS trout facility in Alberta, Canada.

Extracellular vesicles (EVs) are small, lipid bi-layered structures released from various cell types throughout the body. These structures are responsible for the delivery of proteins, compounds, and communication signals across spatial distances. EVs are highly important to diverse biological processes within mammalian systems, including roles in cellular maintenance and homeostasis of physiological conditions and response to infection, and they have the potential to serve as diagnostic hallmarks of infection. Despite these advances and promise, knowledge of the dynamics of EV production and composition during bacterial infection is limited. In this study, we characterize phenotypic traits and proteome remodeling of host EVs derived from murine models during a state of infection by the bacterial pathogen, Klebsiella pneumoniae, compared to an uninfected control. Phenotypic profiling defines consistent size, diameter, and number of EVs from samples across infectious states, whereas a closer look into molecular regulation at the protein level defines core and infection-exclusive proteomes. Within the core proteome (i.e., protein detection common between plasma from uninfected vs. infected samples) clustering based on infectious state was observed and significant increase (p < 0.01) in fibrinogen production upon infection were reported. Conversely, assessment of the infection-exclusive EV proteome supported detection of EVs by Gene Ontology Cellular Component classification revealed an enrichment of proteins associated with blood microparticles, membrane-bound, and the extracellular region, and highlighted the production of immune-associated proteins classified by Gene Ontology Biological Processes. Overall, this study emphasizes complex reprogramming of the host EV proteome upon exposure to K. pneumoniae within a murine model of infection and proposes protein-level signatures indicative of bacterial infection.

Mine tailings are inhospitable to plant establishment because of substrate instability, nutrient limitation, heavy metals, and temperature fluctuations at the soil surface. Biological soil crusts (biocrusts) and their associated microbial communities can initiate primary succession and facilitate plant-soil interactions, thereby supporting ecosystem recovery. Here, we characterized soil bacterial communities beneath biocrusts along a successional gradient in abandoned and rehabilitated molybdenum-bismuth mine tailings in Western Boreal Quebec. We collected 125 soil samples from bare soil, cyanobacterial-, chlorolichen-, and bryophyte-dominated biocrusts, as well as from a mixed bryophyte-lichen cover layer. Bacterial communities were assessed using amplicon sequencing (16S rRNA and nifH genes) and linked to soil physicochemical properties to infer functional potential. Soil pH, electrical-conductivity, and sulfur content were associated with bacterial diversity (distance-based redundancy analysis, R² = 0.20, p < 0.01). Rehabilitated sites exhibited moderate relative abundances of Proteobacteria (6.9%), whereas Actinobacteriota prevailed in nutrient-poor abandoned sites (17.1%), consistent with oligotrophic adaptation. Additionally, functional potential from chemoheterotrophy in later stages was associated with sulfur-oxidation (Spearman's ρ = 0.6, p < 0.05), with anoxygenic photoautotrophs potentially contributing to sulfur oxidation. Overall, our study indicates that bacterial communities may contribute to soil stabilization and could serve as key bioindicators of restoration success.

Although Citrus aurantium has enormous medicinal and ecological value in southern China, little research has been conducted into the composition and functions of endophytic fungi in it. To better explore the characteristics of the endophytic fungal community in C. aurantium, ITS rRNA gene analyses were used to characterize the endophytic fungal microbiome across three plant compartments and three regions. The results showed that a total of 12 109 OTUs were obtained and further divided into 15 phyla and 768 genera. Ascomycota was the dominant phylum. Fusarium, Alternaria, Mortierella, Plectosphaerella, Cladosporium, Colletotrichum, Trichomerium, Botryotrichum, and Aspergillus were the dominant genera. The endemic and dominant genera of endophytic fungi in C. aurantium exhibited plant compartment specificity. The assembly of endophytic fungal communities was dominated by homogeneous selection of deterministic processes. The endophytic fungal genera of C. aurantium predominantly exhibited positive interactions (with a proportion > 99%). The dominant functions of endophytic fungi in C. aurantium were pathotroph and saprotroph. The composition (niche: R² = 0.09, P = 0.001; site: R² = 0.06, P = 0.021) and functional components (niche: R² = 0.117, P = 0.002; site: R² = 0.122, P = 0.006) exhibited significant plant compartment and region specificity. The results of this study reveal the characteristics of the endophytic fungal community of C. aurantium, and provide a theoretical reference for the further development and utilization of endophytic fungal resources.

Listeria costaricensis was recently isolated from a food-processing facility. However, its pathogenic potential and persistence capacity remain poorly characterized at the phenotypic level, raising concerns about food safety. Therefore, we assessed its pathogenic potential through phenotypic invasion and adhesion assays in HeLa cells, showing that L. costaricensis cannot invade HeLa cells despite displaying a cell adhesion capacity comparable to that of Listeria monocytogenes and Listeria innocua reference strains. Given the industrial origin of the strain, we further evaluated its susceptibility to commonly used disinfectants by broth microdilution, finding susceptibility to a mixture of quaternary ammonium compounds (MIC < 100 µg/mL), and reduced susceptibility to peracetic acid (MIC > 160 µg/mL) and sodium hypochlorite (MIC > 500 µg/mL). Considering its demonstrated adhesion capacity, we assessed its ability to form biofilms on polystyrene surfaces, reporting a weak biofilm-forming phenotype comparable to other L. monocytogenes strains. Finally, using the VFanalyzer platform we identified on the L. costaricensis genome 28 virulence-associated gene sequences related to regulatory and structural functions, adherence, and an incomplete invasion gene group compared to L. monocytogenes strains. Collectively, these findings phenotypically support the previously proposed non-pathogenic nature of L. costaricensis, while also revealing a level of persistence comparable to other L. monocytogenes isolates.

Candida albicans is a common commensal yeast and an opportunistic pathogen of global health importance. However, its global geographic and temporal patterns of genetic variation remain poorly understood. Here we analyzed sequence data on seven housekeeping loci from >5000 isolates in the C. albicans PubMLST database representing >60 countries and spanning >70 years. Diploid sequences at each locus were phased into haplotypes to provide higher-resolution insights into diversity, differentiation, and recombination. Our analyses revealed high allelic and genotypic diversities within most geographic and temporal populations. Pairwise FST estimates revealed low but statistically significant differentiation among both geographic and temporal populations, with AMOVA revealing that most genetic variation resides within rather than among subpopulations. STRUCTURE analysis identified two genetic clusters but with extensive admixture within most geographic populations, consistent with frequent gene flow. Phylogenetic and haplotype network analyses revealed evidence of clonal expansion, with globally distributed haplotypes being genetically closer to one another than among more localized haplotypes. Finally, recombination analyses revealed evidence of non-random recombination within populations, including an overall deficiency of heterozygosity, suggesting the importance of parasexuality and/or mitotic recombination in C. albicans populations. Together, these results highlight the global evolutionary dynamics and population structure of C. albicans.

During the COVID-19 pandemic, educators rapidly pivoted their instructional approaches. While this period of disruption is behind us, we are left with a legacy of experiences that can continue to benefit learners. Open educational resources improve accessibility in the classroom, and for learners globally without access to well-resourced institutional libraries. In the 2023-2024 academic year, lecture videos for Veterinary Bacteriology and Mycology (a 3-credit, second year Doctor of Veterinary Medicine (DVM) course at the University of Saskatchewan) were published on YouTube. Two student cohorts were surveyed about their use of the videos, and YouTube analytics was used to describe how videos were accessed globally. Students generally favored these prerecorded videos, citing improved video quality (24%) and shorter duration (36%) compared to other courses where in-person lectures were filmed. Seventy-three percent of students reported that having these videos on YouTube improved accessibility. From August 2023 through December 2024, the YouTube channel received >230 000 views from 86 countries. Approximately 6% of views originated in Canada while 62% were from low- and middle-income countries. This exercise was a positive experience yielding an easy to access repository of content to share with learners locally and globally. Other instructors are encouraged to seek out opportunities for the creation of open resources. Future studies should assess the impacts of online video sharing platforms on student learning.

Highly pathogenic avian influenza clade 2.3.4.4b H5Nx viruses (HPAIVs) have caused significant mortality in wild birds. We investigated active avian influenza virus (AIV) infections and assessed seroprevalence based on general nucleoprotein-specific and H5-specific antibodies in seabirds in Atlantic Canada during 2022-2023. Results were compared to seroprevalence data from 2011 to 2016 to evaluate changes in infection rates following the incursion of HPAIV. We sampled 1073 wild live birds belonging to 14 species. Active H5Nx infections were detected only in 2022, with the highest prevalence in Common Murres (64%), followed by Black-legged Kittiwakes (13%). Differences in seroprevalence were observed between years and species, with both Common Murres and Atlantic Puffins exhibiting higher rates after HPAIV incursion, particularly for anti-H5-specific antibodies. Seroprevalence also differed between locations, and age-related differences in exposure were observed with juvenile birds having much lower seroprevalence than adult birds, particularly among gulls. Despite no active infections being detected in 2023, high seroprevalence across species suggests persisting immunity and/or recent virus circulation. These findings underscore the importance of serological monitoring in tracking AIV dynamics, as antibody detection provides critical insights into past HPAIV exposure even when active infection rates are low.