Canadian journal of microbiology最新文献

As it flows through the collection system, maple sap is likely to be contaminated by microorganisms that colonize the tubing, potentially compromising its quality in terms of physicochemical properties, microbial load, and flavor. This study investigates the effect of microbial inoculation, as protective cultures, on the sap collection system to improve maple syrup quality. The research explored how inoculating collection tubing with specific bacterial strains influences the microbial composition, physicochemical properties (pH, Brix, conductivity, sugars, and organic acids content), and sensory attributes of both maple sap and syrup. Three strains selected for their capacity to produce biofilm on plastic tubing and their impact on maple syrup production from inoculated sap, Pseudomonas sp. MSB2019, Janthinobacterium lividum 100-P12-9, and Pseudomonas fluorescens ATCC 17926, were inoculated to independent sap collection system throughout two sugaring seasons. A non-inoculated system was included. Pseudomonas sp. MSB2019 treatment resulted in a distinct bacterial composition in sap and impact the organoleptic properties of syrup by the end of second flow season, particularly the maple and overall flavor intensity scores were higher. While sap yield and primary microbial load remained unaffected, inoculation treatments corresponded to shifts in flavor attributes of the syrup. These findings indicate that inoculating sap collection systems with targeted strains can positively influence maple syrup quality, particularly in enhancing desirable flavor profiles, suggesting promising applications for syrup production.

Many arthropods, including economically important pests of stored grains, host intracellular bacterial symbionts. These symbionts can have diverse impacts on host morphology, stress tolerance, and reproductive success. The ability to rapidly determine the infection status of host insects and the identity of intracellular symbionts, if present, is vital to understanding the biology and ecology of these organisms. We used a microbiome profiling method based on amplicon sequencing to rapidly screen 35 captive insect colonies. This method effectively revealed single and mixed infections by intracellular bacterial symbionts, as well as the presence or absence of a dominant symbiont, when that was the case. Because no a priori decisions are required about probable host-symbiont pairing, this method is able to quickly identify novel associations. This work highlights the frequency of endosymbionts, indicates some unexpected pairings that should be investigated further, such as dominant bacterial taxa that are not among the canonical genera of endosymbionts, and reveals different colonies of the same host insect species that differ in the presence and identity of endosymbiotic bacteria.

M13 bacteriophages form self-assembled nanorods with the ability to self-assemble into complex materials with higher-order structures. These features make them useful templates for material fabrication. Their use in soft materials, bio-nano systems, and biomedical applications is well established. For these bio-interfacial applications, it is crucial that phages remain biocompatible and their production sustainable. Here, we review the bioprocessing of M13 phages and genetic engineering strategies that retain their natural assets in nanomaterials or bulk materials. Specifically, we highlight the extensively studied fermentation process of M13 phages with Escherichia coli (E. coli) and common downstream processing methods suitable for materials manufacturing. The ease of phage production contributes to its wide use for phage display, enabling the creation of large libraries of functional mutants. For materials purposes, genetic engineering often targets the pIII and pVIII proteins, enabling different geometries and fragment sizes. We also review common peptides displayed on phages, including arginine-glycine-aspartic acid (RGD) peptides, used for surface plasmon resonance (SPR) probes, targeted medicine, cell regeneration, or tissue scaffolding. We study glutamate-modified phages for metal binding, biomineralization, and electronics in bulk materials. By considering self-assembly, bioprocessing, and genetic engineering, material engineers can fully harness M13 phages for diverse functional and sustainable devices.

Pyrimidine base and ribonucleoside salvage metabolism was investigated in Pseudomonas putida ATCC 17536 cells. In ATCC 17536 cell extracts, the pyrimidine ribonucleoside salvage enzymes nucleoside hydrolase and cytosine deaminase activities were measurable, while uridine phosphorylase activity was not. Carbon and nitrogen sources influenced the levels of the salvage pathway enzyme activities in P. putida ATCC 17536. Catabolite repression by a glucose metabolite of nucleoside hydrolase and cytosine deaminase synthesis in ATCC 17536 cells compared to cells grown on the carbon source succinate or ribose was observed, while a nitrogen metabolite appeared to be controlling pyrimidine salvage enzyme synthesis. When glucose was the carbon source, ATCC 17536 cells grown on uracil or 5-methylcytosine as a nitrogen source caused at least a five-fold increase in hydrolase and deaminase synthesis relative to their activities in ammonium sulfate-grown cells. In succinate-grown ATCC 17536 cells, thymine or 5-methylcytosine as a nitrogen catabolite produced at least double the hydrolase or deaminase activity relative to either activity in ammonium sulfate-grown cells. Overall, the pyrimidine base and ribonucleoside salvage enzymes in P. putida ATCC 17536 biovar B cells were regulated by the carbon or nitrogen source with pyrimidine salvage metabolism differing in biovar A and B strains.

Highly pathogenic avian influenza (HPAI) H5N1 has caused the deaths of more than 100 million birds since 2021, and human cases since 1997 have been associated with significant morbidity and mortality. Given recent detections of HPAI H5N1 in dairy cattle and H5N1 RNA detections in pasteurized retail milk in the United States, we established the pan-Canadian Milk Network in April 2024. Through our network of collaborators from across Canada, retail milk was procured longitudinally, approximately every 2 weeks, and sent to a central laboratory to test for the presence of influenza A virus RNA. Between 29 April and 17 July 2024, we tested 109 retail milk samples from all 10 Canadian provinces (NL, NS, PEI, NB, QC, ON, MB, SK, AB, and BC). All samples tested negative for influenza A virus RNA. This nationwide initiative was established for rapid retail milk screening as per the earliest reports of similar undertakings in the United States. Our independent testing results have aligned with reporting from federal retail milk testing initiatives. Despite no known HPAI infections of dairy cattle in Canada to date, H5N1 poses a significant threat to the health of both humans and other animals. By performing routine surveillance of retail milk on a national scale, we have shown that academic networks and initiatives can rapidly establish nationwide emerging infectious disease surveillance that is cost-effective, standardized, scalable, and easily accessible. Our network can serve as an early detection system to help inform containment and mitigation activities if positive samples are identified and can be readily reactivated should HPAI H5N1 or other emerging zoonotic viruses be identified in agricultural or livestock settings, including Canadian dairy cattle.

Whole-genome sequence-based surveillance of bacteria for determinants of antimicrobial resistance (AMR) promises many advantages over traditional, wet-lab approaches. However, adjustments to parameters used to identify genetic determinants from sequencing data can affect results and interpretation of the important determinants in circulation. Using a dataset of whole-genome sequences from 1633 isolates of Salmonella Heidelberg and S. Kentucky collected from surveillance of Canadian poultry production, we queried the genomic data using an in silico AMR detection tool, StarAMR, applying a range of parameter values required for the detection pipeline to test for differences in detection accuracy. We compared the results from each iteration to phenotypic antimicrobial susceptibility results, and generated estimates of sensitivity and specificity using regression models that controlled for the effects of multiple sampling events and variables, and interactions between covariates. Results from our analyses revealed small, yet significant effects of the input parameters on the sensitivity and specificity of the AMR detection tool, and these effects differed based on the serovar and drug class in question. Findings from this study may have implications for the incorporation of whole-genome sequence-based approaches to the surveillance of AMR determinants in bacteria sampled from food products and animals related to food production.

This study investigated the cecal microbiome of broilers raised under specific antimicrobial feeding programs (AFPs). A total of 2304 day-old Ross-708 male (M, n = 1152) and female (F, n = 1152) chicks were distributed into 48 floor pens which were allocated to one of three AFPs: Conventional, raised without medically important antibiotics (RWMIA), and raised without antibiotics (RWA). At 28 (D28) and 41 (D41) days of age, cecal contents were collected for culture dependent and independent analyses. At both 28 and 41 days, Enterococcus was more abundant in RWA-raised broilers than other groups with the most abundance of this bacterium being found in female birds (P < 0.05). At D41, the most abundant Eimeria tenella counts was observed in RWA-raised broiler ceca (P < 0.05). Sex effects were observed on the abundances of four of the 248 identified antimicrobial resistance genes while abundances of 10 were modulated by AFPs (P < 0.05). Ceca of females birds showed more tssB than males, and ceca of RWMIA-raised birds contained the highest abundance of chuY genes regardless of sex. This study showed that in a specific feeding program, cecal resistome can be affected by chicken's sex contributing to understand the AMR related to the AMU.

The Cryptococcus neoformans and Cryptococcus gattii species complexes are the etiological agents of cryptococcosis, a disease responsible for 181 000 deaths annually worldwide due to late diagnosis and limited treatment options. Studies focusing on the identification of new substances with antifungal activity, such as essential oils (EOs), are urgently needed. While the antifungal effects of EO have already been suggested, their mechanism of action at the molecular level still requires evaluation. In this work, we assessed the molecular changes induced by the exposure of Cryptococus neoformans (H99) and Cryptococcus deuterogatti (R265) to lavender essential oil (LEO) using a morphological and proteomics approach. The identified proteins were categorized by Gene Ontology according to biological processes and molecular functions, and Kyoto Encyclopedia of Genes and Genomes pathway analysis was also conducted. Our findings indicate that LEO creates a stressful environment in both strains; however, the response to this stimulus differs between the two species. In C. neoformans, changes were observed in energy metabolism and pathways related to alternative sources of energy and oxidative stress response. In C. deuterogatti, changes were identified in pathways related to cellular architecture, implying that the cell underwent morphological changes such as membrane and cell wall stiffening.

This study investigates the composition, structure, and predictive associated functions of epilithic bacteria living in the biofilms of a freshwater (FWR) and a mixed-saline (MSR) tropical river. High-throughput sequencing revealed a 69% overlap in species richness between the two sites. Cyanobacteria were dominant in freshwater, while heterotrophic classes like Alphaproteobacteria and Betaproteobacteria were prevalent in the mixed-saline biofilm. Predictive functional analysis (FAPROTAX) indicated greater diversity in MSR, favoring organic matter degradation and nutrient cycling, with more bacterial OTUs involved in chemoheterotrophy and hydrogen oxidation (Wilcoxon, p > 0.001). In contrast, FWR had a higher abundance of OTUs linked to phototrophy and degradation of aromatic compounds and plastics (Wilcoxon, p > 0.001). Key microbial interactions were revealed between phototrophic cyanobacteria and heterotrophs such as Fulvivirga (Cytophagia), suggesting a pivotal role for this genus in the carbon cycle. Additionally, bacterial species known for their ability to remove chlorine from pollutants, such as Acidovorax, Acinetobacter, Comamonas, Curvibacter, Sediminibacterium, or bacterial species belonging to the Sphingomonadaceae family were more diverse and abundant in FWR site. These findings point to promising bioremediation potential driven by biofilm community activities, particularly in tropical freshwater environments impacted by organochlorine contaminants.

Between 2022 and 2025, high pathogenicity avian influenza (HPAI) H5N1 clade 2.3.4.4b was detected in poultry and wildlife across most countries in Central and South America. The epizootic peaked in 2023, subsided in 2024, and resurged in 2025. In Central America, outbreaks in wildlife were few and small, and mostly affected pelicans. In contrast, South America experienced unprecedented mass mortality in colonial seabirds and pinnipeds, including endangered and endemic species. Notably, viral adaptation enabled mammal-to-mammal transmission in pinnipeds and rapid viral spread across multiple countries along the Pacific and Atlantic coasts. Subsequent introductions to subantarctic islands and Antarctica stemmed from South American viruses. In February 2025, a novel reassortant virus emerged, recombining HPAI H5N1 B3.2 genotype with South American low pathogenicity avian influenza viruses. In May 2025, HPAI H5N1 viruses re-emerged in Brazil, causing a series of outbreaks in poultry and wild birds. The ongoing circulation and evolution of HPAI H5N1 in this region underscores the need for strengthened surveillance, expanded genomic monitoring, and enhanced integration of wildlife conservation and environmental sectors in regional response frameworks.