Canadian journal of microbiology最新文献

Aspergillus fumigatus is a globally distributed mold and a major cause of opportunistic infections in humans. Because most infections are from environmental exposure, it is critical to understand environmental populations of A. fumigatus. Soil is a major ecological niche for A. fumigatus. Here, we analyzed 748 soil isolates from 21 locations in six provinces and one territory in Canada. All isolates were genotyped using nine microsatellite markers. Due to small sample size and/or close proximities for some local samples, these isolates were grouped into 16 local geographic and ecological populations. Our results indicated high allelic and genotypic diversities within most local and provincial populations. Interestingly, low but statistically significant genetic differentiations were found among geographic populations within Canada, with relatively similar proportions of strains and genotypes belonging to two large genetic clusters. In Hamilton, Ontario, and Vancouver, BC, where two and three ecological populations were analyzed, respectively, we found limited genetic difference among them. Most local and provincial populations showed evidence of both clonality and recombination, with no population showing random recombination. Of the 748 soil isolates analyzed here, two were resistant to triazole antifungals. We discuss the implications of our results to the evolution and epidemiology of A. fumigatus.

Vibrio parahaemolyticus produces a key virulent factor known as thermostable direct hemolysin (TDH). TDH exhibits diverse biological activities, including hemolytic activity. The β-type hemolysis observed on Wagatsuma agar due to TDH is recognized as the Kanagawa phenomenon (KP). The tdh2 gene is primarily responsible for TDH production and the associated KP. AcsS was originally identified as an activator of swimming and swarming motility in V. parahaemolyticus. However, its potential roles in other cellular pathways remain unclear. In this study, we investigated the regulatory effects of AcsS on the hemolytic activity and tdh2 expression in V. parahaemolyticus using phenotypic tests for KP, quantitative real-time polymerase chain reaction, LacZ fusion, and electrophoretic mobility shift assays. The data showed that V. parahaemolyticus hemolytic activity and tdh2 transcription were under the negative control of AcsS. Additionally, in-vitro binding assays revealed that His-AcsS could not bind to the regulatory DNA region of tdh2. However, overexpression of AcsS in an Escherichia coli strain suppressed the expression of tdh2. Collectively, these results suggested that AcsS suppresses the hemolytic activity of V. parahaemolyticus through the downregulation of tdh2 transcription. The data enhanced our understanding of the regulatory networks governing tdh2 expression and the roles of AcsS in this bacterium.

Escherichia coli is a Gram-negative bacterium that is ubiquitous in animals and humans, with some strains capable of causing disease. The aim of this study was to perform a comparative genomic analysis of 2732 generic E. coli isolates that were recovered from poultry samples collected from six regions in Canada as part of the National Microbiological Baseline study in Broiler Chicken. Isolates were subjected to whole genome sequencing and a subset (1122/2732) were tested for phenotypic resistance to 15 antimicrobials. These E. coli isolates were highly diverse, representing 376 serotypes, 236 sequence types and 21 pathotypes, of which 19 were hybrid pathotypes. A high concordance (>85%) between resistance phenotype and the presence of antimicrobial resistance genes and point mutations (resistance determinants) was observed for 13/15 antimicrobials. Over 95% of the β-lactam, fluoroquinolone, and phenicol resistance genes were predicted to be plasmid-borne. The number of resistance determinants per genome was highest in Quebec, while resistance genes associated with β-lactam resistance were more frequently detected in isolates from British Columbia. Generic E. coli in Canadian poultry are highly diverse, can carry pathotype-associated virulence factors and resistance determinants of clinical significance with a risk of emerging into pathogenic strains.

Ciprofloxacin is important for treatment of severe or invasive Salmonella infections in humans. As laboratories transition from phenotypic to genomics-based methods for determining ciprofloxacin non-susceptibility, it is important to define the correlation between genetic determinants of resistance and phenotypic outcomes. Here, we examined ciprofloxacin resistance mechanisms in Salmonella and tested the hypothesis that isolates containing only one mechanism had intermediate resistance while isolates containing two or more mechanisms had full resistance according to breakpoints from the Clinical Laboratory Standards Institute. Among 13 750 human and food/animal Salmonella enterica isolates, 2325 were predicted to be non-susceptible to ciprofloxacin using whole genome sequencing and Staramr. The most common mechanisms of resistance were mutations in gyrA (especially S83F and D87N/D87Y) and the qnrB19 allele. Only 28% of ciprofloxacin resistant isolates had two or more resistance mechanisms; the remainder contained only one mechanism. Of isolates with two or more mechanisms, only 63% were resistant. Thus, the number of genetic determinants of ciprofloxacin resistance in an isolate could not reliably differentiate the ciprofloxacin intermediate or resistant categories when using North American breakpoints. Predicting ciprofloxacin intermediate/resistant as a single non-susceptible category would facilitate global standardization of data to inform public health surveillance, treatment guidelines, and stewardship.

Incorporating shrub willow chips into soil may improve the chemical, physical, and biological properties of soils with low organic matter but the impact on soil microbial communities and their dynamics is not known. We assessed changes in the soil microbial communities in response to willow chip applied at increasing rates (0, 20, 40, and 60 Mg ha^-1) in a potato-barley cropping system. Bacterial and fungal community diversity, relative abundance, and potential functions were assessed using amplicon sequencing of 16S and ITS rRNA genes at six time points. High rates (40 and 60 Mg ha^-1) of willow chips had no effect on bacterial alpha diversity but significantly decreased fungal alpha diversity (Shannon) while increasing fungal richness (Chao-1). At rates of 40 Mg ha^-1 and higher, the relative abundance of copiotrophic bacterial groups increased, while that of copiotrophic fungal groups decreased. The relative abundance of the most dominant microbial phyla and genera varied over time, with copiotrophic groups declining and oligotrophic groups increasing. High willow chip application rates increased bacterial molecular markers related to carbon fixation and degradation, nitrogen fixation, and phosphorus solubilization, while decreasing markers related to cellobiose transport and denitrification. This study demonstrates the ability of willow chips to influence the microbial community composition and potential function over time.

The livestock industry has been a source of concern in terms of antimicrobial resistance (AMR) development and spread, especially from a One Health perspective. Raising livestock without antimicrobials, so called natural (NAT) production, is an increasingly popular practice. This study used metagenomics to compare this practice to conventional (CONV) antimicrobial use (AMU) on the microbiome and resistome in the feces of beef cattle and swine and the cecal contents of broiler chickens. In cattle, Bacteroidetes, Euryarchaeota, and Spirochaetes were more abundant (q < 0.01) in CONV than NAT systems, with no differences (q > 0.05) in bacterial profiles in either swine or chickens. Classes of antimicrobial resistant genes (ARG) were not impacted regardless of AMU in any of the livestock species. However, many tetracycline resistance genes were more abundant in CONV as compared to NAT swine (q < 0.05), but this difference was not observed in cattle or chickens. This study confirmed that elimination of AMU does not necessarily result in an immediate decline in the abundance or diversity of ARGs within a single livestock production cycle.

Syphilis cases have been consistently rising since its near elimination in the late 1990s. This resurgence, along with increasing rates of macrolide resistance and congenital syphilis, has triggered renewed efforts to better understand and control the disease. We analyzed 827 Treponema pallidum genomes and created a new genome-based hierarchical lineage framework, recapitulating the major T. pallidum lineages and characterizing sub-lineages. An updated pangenome was constructed, revealing that T. pallidum subsp. pallidum lineages are determined by a single hypothetical major outer sheath C-terminal domain-containing gene, while no significant genetic difference was observed between T. pallidum subsp. pertenue and T. pallidum subsp. endemicum. This study introduces an integrated genomic approach to characterize T. pallidum and highlights the significance of pangenomes in supporting public health.

Acadesine (AICAR) is a promising candidate for new drugs in Phase III clinical trials. The purpose of this study is to analyse the steps in the biosynthesis pathway of AICAR. Our previous study found that overexpression of veA, a gene encoding a global regulator, significantly increased AICAR production of endophytic Fusarium solani HB1-J1 and the anti-tumor activity of its extracts. Transcriptome and metabolome analysis of FsveA^OE14, a veA overexpressing F. solani strain, revealed a 10-step AICAR synthesis pathway, with adenylosuccinate lyase PurB as a key enzyme. Generally, overexpressing purB (the gene encoding adenylosuccinate lyase) enhances AICAR synthesis. However, in FsveA^OE14, despite down-regulation of purB, AICAR content increased, which is contradictory. Further studies revealed that expression levels of purB homologs gene, pro06469 and pro10879, were upregulated in FsveA^OE14. This suggests that although veA overexpression leads to purB down-regulation, their up-regulation may compensate for the reduction of purB, thus affecting AICAR synthesis. Additionally, compared to the wild type, overexpressing purB significantly enhances the inhibitory activity of the strain's extracts against the nonsmall-cell lung cancer cell line A549. Furthermore, it also increases the metabolic levels of other anti-tumor compounds, including 3-methyladenine, taurine, and others. These results indicate that VeA regulates AICAR biosynthesis via key enzymes like PurB, enhancing AICAR and other anti-tumor compound production, thus increasing the anti-tumor activity of F. solani extracts.

Colletotrichum gloeosporioides is a destructive pathogen that causes significant economic and ecological losses in agricultural and forestry production. In search of effective biocontrol agents, this study isolated an endophytic fungus, Coniochaeta velutina, from healthy Camellia oleifera leaves and investigated its in vitro inhibitory mechanism on Colletotrichum gloeosporioides using transcriptomics and metabolomics analyses. These findings were used to evaluate the differences in gene expression and metabolite content between the treatment (Coniochaeta velutina-treated Colletotrichum gloeosporioides) and control (untreated Colletotrichum gloeosporioides) groups. The transcriptomic analysis detected a total of 15 310 expressed genes, with 3938 showing significant differential expression (p < 0.05) (2093 upregulated and 1845 downregulated genes). These genes were enriched primarily in the following pathways: mitogen-activated protein kinase (MAPK) signalling, antibiotic biosynthesis, amino acid metabolism, carbon metabolism, and peroxidase pathways. Metabolomic analysis revealed 452 metabolites in both groups, with 138 showing significant differences. These genes were enriched mainly in secondary metabolite biosynthesis, amino acid biosynthesis, and α-linolenic acid metabolism. Transcriptome and metabolome association analyses, along with qRT-PCR results, revealed that the levels of intracellular pectolinarigenin metabolites significantly increased in the treatment group, leading to disrupted MAPK signalling and reduced amino acid biosynthesis, which are essential for maintaining normal cell growth. Notably, the decrease in terpenoid compounds was the primary reason that Colletotrichum gloeosporioides was inhibited by the biocontrol fungus Coniochaeta velutina. Therefore, these findings provide valuable insights into the biocontrol mechanisms of Coniochaeta velutina against Colletotrichum gloeosporioides and offer a promising foundation for the development of new anthracnose prevention and control strategies.

In northern ecosystems such as the subarctic tundra, mining activities increase stress to a point where actions are needed to promote site reclamation. Ecological restoration of these mining-impacted sites with beneficial microorganisms, such as mycorrhizal fungi, is considered necessary and useful for the growth and survival of their host plants, but also for their tolerance to poor and contaminated environments, such as mine tailings. Here, we are interested in root symbionts associated with plants from the Schefferville mining site in northern Quebec. Very few studies of root fungal communities have been conducted in such a northern environment. The spatial and host plant variation of root fungal isolates was investigated. A total of 456 culturable fungi were isolated, of which 376 were successfully identified and assigned to 106 taxa based on rDNA internal transcribed spacer analysis using ITSF-1 and ITS-4 primers. The most commonly isolated fungi belonged to three genetically related groups: the Rhizoscyphus ericae aggregate, the dark septate endophytes, and Umbelopsis rammaniana and Mortierella sp., which are known to be genetically very close and often misclassified as one another. These groups were present on both disturbed and natural sites, but it appears that plants from disturbed sites had a greater affinity for dark septate endophytes. This study is the first step in the development of a restoration plan for the Schefferville mining site, and the baseline data obtained open new avenues for future studies, including the use of indigenous mycorrhizal-based biofertilizers to implement ecological revegetation strategies.