Canadian journal of microbiology最新文献

Bacterial biofilm production is linked to its adaptive capacity to environments throughout its lifecycle. This study aimed to assess the variability in biofilm formation (BF) dynamic by Salmonella enterica and to explore the potential impact of the cell's prior history, primarily shaped by strain and its isolation source. In vitro BF of 141 S. enterica strains isolated from animal-origin foods, plant-based foods, unspecified food sources, the environment, and clinical cases, was evaluated using the crystal violet assay at 25 °C for up to 72 h. Kruskal-Wallis test was used to assess the effect of time, source, and strain. The Aryani method was used to characterize microbial response variability. The BF capacity of S. enterica strains ranged from 0.07 to 2.3, 0.07 to 2.7, and 0.06 to 2.7OD_595nm at 24, 48, and 72 h, respectively. At 24 h (66.0%; 93/141) and 48 h (56.0%; 79/141), most isolates were classified as nonbiofilm producers, while at 72 h, the majority were weak biofilm producers (39.7%; 56/141). Time, strain, and isolation source significantly influenced BF, with an overall increase in BF occurring over time, and clinical strains being the highest biofilm producers. Strain to strain variability was the highest contributor to the total variance ( ${\sigma }_{24h}^2$ = 0.18OD_595nm ², ${\sigma }_{48h}^2$ = 0.23OD_595nm ², ${\sigma }_{72h}^2$ = 0.26OD_595nm ²). Analysis of variability between and within isolation source groups revealed the highest variability among clinical isolates ( ${\sigma }_{24h}^2$ = 1.08OD_595nm ², ${\sigma }_{48h}^2$ = 1.36OD_595nm ², ${\sigma }_{72h}^2$ = 1.38OD_595nm ²). Although BF was statistically associated with the strain and its isolation source, the high variability observed within these factors suggests that they alone are insufficient to explain how the cell's prior history influences BF. A more comprehensive undertanding on BF will require considering additional intrinsic and extrinsic factors.

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.

A species of Morchella was observed growing in spring, under a vulnerable member of the Proteaceae, in the Cape Floristic Region of South Africa. These fungi shared many of the cryptic characteristics common in the genus Morchella and displayed a wide range of phenotypic expression. The unique ecology of these fungi and the fact that no endemic Morchella species have been described from Africa lead to suspicions that this could be a novel species. Sequencing of key genetic regions, phylogenetics, and morphological studies confirmed that this was indeed a previously unknown species of Morchella. Roots collected underneath the fruiting bodies displayed a range of root-associated activities, alluding to a possible relationship. Further, this Morchella species has a history of traditional use on the Cape Peninsula of South Africa. The traditional use of fungi is rarely recorded in Africa. In this study, we introduce Morchella capensis sp. nov., the first endemic African morel.

This expansion for the modular vector assembly platform BEVA (Bacterial Expression Vector Archive) introduces 11 new BEVA parts including two new cloning site variants, two new antibiotic resistance modules, three new origins of replication, and four new accessary modules. As a result, the modular system is now doubled in size and expanded in its capacity to produce diverse replicating plasmids. Furthermore, it is now amenable to genetic engineering methods involving genome-manipulation of target strains through deletions or integrations. In addition to introducing the new modules, we provide several BEVA-derived Golden Gate cloning plasmids that are used to validate parts and that may be useful for genetic engineering of proteobacteria and other bacteria. We also introduce new parts to allow compatibility with the CIDAR MoClo parts libraries.

Highlights: S. Heidelberg survived up to 21 days in PWS which is often used as broiler bedding. S. Heidelberg abundance and survival was correlated with the water activity of PWS. S. Heidelberg strains that carried higher copy numbers of small Col plasmids were the dominant strains isolated from PWS at later time points. S. Heidelberg strains harboring transmissible plasmid carrying AmpC-like beta-lactamase gene persisted longer in PWS without antibiotic pressures for AMR.

The objective of this study was to compare chlorhexidine digluconate and other antibiotics susceptibility of four species of theAcinetobacter baumannii complex, and further investigate the chlorhexidine digluconate (CHG) tolerance mechanisms and molecular epidemic characteristics. Of 889 A. baumannii complex isolates, A. baumannii, A. nosocomialis, A. pittii, and A. seifertii accounted for 84.2%, 10.9%, 3.4%, and 1.5%. Acinetobacter baumannii was generally resistant to all tested antibiotics, while other three species were commonly more susceptible; 92.1% (313/340) CHG-tolerant A. baumannii, 19.6% (19/97) CHG-tolerant A. nosocomialis, 3.3% (1/30) CHG-tolerant A. pittii, and 15.4% (2/13) CHG-tolerant A. seifertii were identified. Furthermore, compared to A. baumannii ATCC 19606, upregulated expression was found in qacE_Δ1, fabI, and efflux pump encoding genes in CHG-tolerant A. baumannii, but the expression level of oprD was reduced. Additionally, only the expression level of fabI was increased in the CHG-tolerant A. nosocomialis, and the expression level of adeG was increased in the CHG-tolerant A. pittii and A. seifertii. Furthermore, CHG-tolerant A. baumannii may have a relatively high clonal correlation, the predominant sequence type of which was ST208 (90%, 36/40). It is rather necessary to identify specific species members among the A. baumannii complex for clinical treatment options and antibiotics resistance monitoring.

This study employed Illumina HiSeq high-throughput sequencing technology to analyze the V4-V5 regions of myxobacterial 16S rRNA in rhizosphere and nonrhizosphere soils of Haloxylon ammodendron in the saline-alkaline wetland of Ebinur Lake, with the aim of investigating the community structure and diversity of myxobacteria. Results indicated that myxobacterial communities in rhizosphere soils exhibited greater diversity and richness compared to nonrhizosphere soils. Soil physicochemical properties, particularly moisture content, were identified as key environmental factors influencing myxobacterial diversity. The halotolerant genus Haliangium was found to be predominant under saline-alkaline conditions. Additionally, myxobacteria demonstrated distinct ecological specificity and environmental adaptability between rhizosphere and nonrhizosphere soils. For example, the genus Enhygromyxa exhibited a negative correlation with soil moisture content in rhizosphere soils but a positive correlation with soil electrical conductivity in nonrhizosphere soils. Co-occurrence network analysis revealed complex interaction patterns among myxobacterial genera and other bacterial genera, with closer interactions observed in rhizosphere soils. This study highlights the importance of environmental factors in regulating microbial community structure and function in saline-alkaline wetlands, providing new insights into the ecological roles and interaction mechanisms of myxobacteria within the ecosystem.

RNA-Seq analysis of Mesorhizobium japonicum infected by phage Cp1R7A-A1 (full name vB_MloS_Cp1R7A-A1) revealed the transcription of all 237 putative phage genes, including 27 tRNA and 210 protein-encoding genes. All predicted protein-encoding genes of Cp1R7A_A1 showed expression. The phage tRNA genes also showed a notable expression, indicating a possible tRNA-dependant phage survival strategy. Host genes related to nutrient uptake and energy metabolism were significantly upregulated within 1-2 h post infection, likely reflecting the phage's metabolic demands. Notably, peptidoglycan-cleaving enzymes showed elevated expression after 3 h, suggesting host stress responses. These findings show the transcriptional interplay between phage Cp1R7A-A1 and M. japonicum, providing a foundation for future functional studies.

Surveillance methods for antimicrobial resistance genes (ARGs) are needed to assess potential risk of antimicrobial resistance, especially in complex environmental samples with limited data on ARG distribution. This study employed target-enrichment metagenomics (bait-capture) and a Resistomap qPCR assay to assess the resistome in marine and freshwater sediments associated with active Canadian finfish aquaculture operations. Differences in resistome profiles were considered with distance to the net-pens, concentrations of three aquaculture-associated chemical residues, and microbial communities as detected with 16S rRNA gene amplicon sequencing. With bait-capture, a total of 194 ARGs and 41 replicon types were detected across the sediment samples. Differences due to aquaculture proximity were noted in the composition of the resistome, which was dominated by tetracycline resistance genes. With qPCR, 37 out of 51 ARGs targets were detected, and proximity to net-pens or region did not show changes in resistome composition. Co-occurrence networks revealed significant correlations among genera and the resistome detected with bait-capture, highlighting a potential influence of aquaculture on ARGs in the environment. This study demonstrates the utility of bait-capture and qPCR assays in detection of ARGs in both freshwater and marine sediments from aquaculture sites that will assist further ARG surveillance.