Canadian journal of microbiology最新文献

The use of Trichoderma in agriculture as both a biocontrol agent and biofertilizer hinges on its ability to colonize the rhizosphere, promote plant growth, endure adverse environments, compete for space and nutrients, and produce enzymes and secondary metabolites to mycoparasitize and infect other fungus. In humans, Trichoderma exhibits the capacity to infect various bodily tissues, leading to Trichodermosis. There has been a notable increase in cases ranging from superficial to fatal, invasive, and disseminated infections, particularly among immunocompromised individuals. Trichoderma species employ diverse strategies to colonize and survive in various environments, infecting phytopathogens; however, the mechanisms and virulence factors contributing to human infections remain poorly understood. In this mini review, we provide a brief overview and contextualization of the virulence mechanisms employed by Trichoderma in parasitizing other fungi, as well as those implicated in modulating plant immunity and inducing human infections. Furthermore, we discuss the similarity of these virulence factors capable of modulating the mammalian immune system and their potential implications for human infection.

On solid substrates, biofilms develop rich wrinkle morphologies during its growth. Based on the thin film buckling theory, we established a local three-dimensional biofilm/substrate buckling model, and explored the effects of mechanical forces, elastic modulus of the substrate, and biofilm thickness on the wrinkle morphology. We simulated the wrinkle evolution in various patterns of Bacillus subtilis biofilm growing on agar substrates with different stiffness and found that the biofilm wrinkling process is the process of internal energy release. The stiffness of the substrate changes the wrinkling time of the biofilm; The biofilm wrinkle morphology (patterns II, III, and IV) U_internal and U_internal/U₀ decrease with nutrient consumption, and the biofilm evolves towards lower energy consumption. In the early stages of biofilm growth (patterns I, II, and III), the harder the agar substrate, the larger the U_friction and U_friction/U₀, which is less conducive to biofilm expansion.

Rhizobia are soil-dwelling proteobacteria that can enter into symbiotic nitrogen-fixing relationships with compatible leguminous plants. Taxonomically, rhizobia are divided into alpha-rhizobia, which belong to the class Alpharoteobacteria, and beta-rhizobia, which belong to the class Betaproteobacteria. To date, all bona fide alpha-rhizobia belong to the order Hyphomicrobiales. However, a recent study suggested that Sphingomonas sediminicola DSM 18106^T is also a rhizobium and is capable of nodulating pea plants (Pisum sativum), which would expand the known taxonomic distribution of alpha-rhizobia to include the order Sphingomonadales. Here, we attempted to replicate the results of that previous study. Resequencing and computational analysis of the genome of S. sediminicola DSM 18106^T failed to identify genes encoding proteins involved in legume nodulation or nitrogen fixation. In addition, experimental plant assays indicated that S. sediminicola DSM 18106^T is unable to nodulate the two cultivars of pea tested in our study, unlike the rhizobium Rhizobium johnstonii 3841^T. Taken together, and in contrast to the previous study, these results suggest that S. sediminicola DSM 18106^T is not capable of inducing root nodule formation on pea, meaning that the taxonomic distribution of all known alpha-rhizobia remains limited to the class Hyphomicrobiales.

DNA synthesis and assembly techniques have enabled the creation of validated and standardized DNA parts, used for producing proteins, enzymes, and small molecules. However, most DNA parts are governed by Material Transfer Agreements, which restrict sharing and reuse for commercial purposes even in the absence of patents, bottlenecking innovation. DNA synthesis, crucial for producing new parts, also remains expensive and therefore inaccessible to most researchers. With the breakneck pace of digital innovations for designing and learning from biology, a new and more open approach to the physical building and testing of biology is needed. We propose the establishment of an Open Bio Research Alliance, to create and distribute open collections of DNA and other biological parts, combined with regulated and affordable DNA synthesis services. Focusing on Canada's bioeconomy, establishing domestic DNA synthesis infrastructure would not only secure global competitiveness in engineering biology, but also safeguard biosecurity and national sovereignty over critical resources. By harnessing and supporting existing lab automation resources, the Alliance will also help scale the building and testing of engineered biological systems. Leveraging these tools and strategies, Canada is well-positioned to lead the world in open and innovative biotechnology, paving the way for a thriving bioeconomy.

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.

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.

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.