Canadian Journal of Microbiology
ISSN / EISSN : 0008-4166 / 1480-3275
Published by: Canadian Science Publishing (10.1139)
Total articles ≅ 12,447
Latest articles in this journal
Canadian Journal of Microbiology; https://doi.org/10.1139/cjm-2021-0284
While monitoring the presence of antibiotic resistance in municipal wastewater bacteria from Mexico City, five Escherichia coli isolates were detected to be resistant to carbapenems, antibiotics of “last resort” used mostly in hospitals. Further analysis revealed that these carbapenem-resistant isolates carried the gene for a metallo-beta-lactamase, NDM-5. The gene was found to be beared by a large, ~145 kb conjugative plasmid, which also carries putative genes encoding resistance to sulfonamides, trimethoprim, tetracycline, ciprofloxacin, chloramphenicol (although no phenotypic chloramphenicol resistance was detected) and quaternary-ammonium compounds. The plasmid also carried gene mobility determinants, such as an integron integrase, and two transposases. In addition to the direct public health threat posed by the presence of such multi-resistant organisms in wastewater released into the environment and used for crop irrigation; it is particularly concerning that carbapenem-resistant E. coli is rather rare in Mexican hospitals (<1%), but was found in small, 100-mL samples of municipal wastewater. This could suggest that, either these organisms are under-reported by clinical microbiology laboratories, underlining the usefulness of wastewater monitoring; or that there is an unknown source of such carbapenem-resistant organisms that are being dumped into the wastewater. The source of these bacteria must be assessed and controlled to prevent the further spread of this multi-resistance plasmid among other environmental and clinical microorganisms.
Canadian Journal of Microbiology; https://doi.org/10.1139/cjm-2021-0225
Canada is currently implementing a site selection process to identify a location for a deep geological repository (DGR) for the long-term storage of Canada’s used nuclear fuel, wherein used nuclear fuel bundles will be sealed inside copper-coated carbon steel containers, encased in highly compacted bentonite clay buffer boxes and sealed deep underground in a stable geosphere. Because a DGR must remain functional for a million years, there is value to examining ancient natural systems that serve as analogues for planned DGR components. Specifically, studying the microbiology of natural analogue components of a DGR is important for developing an understanding of the types of microorganisms that may be able to grow and influence the long-term stability of a DGR. This study explored the abundance, viability, and composition of microorganisms in several ancient natural analogues using a combination of cultivation and cultivation-independent approaches. Samples were obtained from the Tsukinuno bentonite deposit (Japan) that formed ~10 mya, the Opalinus Clay formation (Switzerland) that formed ~174 mya, and Canadian shield crystalline rock from Northern Ontario that formed ~2.7 bya. Analysis of 16S rRNA gene amplicons revealed that three of the ten Tsukinuno bentonite samples analyzed were dominated by putative aerobic heterotrophs and fermenting bacteria from the Actinobacteria phylum, whereas five of the Tsukinuno bentonite samples were dominated by sequences associated with putative acidophilic chemolithoautotrophs capable of sulfur reduction.
Canadian Journal of Microbiology pp 1-11; https://doi.org/10.1139/cjm-2020-0590
Microbes play vital roles in soil quality; however, their response to N (nitrogen) and P (phosphorus) fertilization in acidic paddy soils of subtropical China remains poorly understood. Here, a 10-year field experiment was conducted to evaluate the effects of different fertilization treatments on microbial communities by Illumina MiSeq sequencing. The results showed that different fertilization treatments did not exert a significant effect on microbial alpha diversity, but altered soil properties, and thus affected microbial community composition. The microbial communities in the T1 (optimized N and P fertilizer) and T2 (excessive N fertilizer) treated soils differed from those in the T0 (no N and P fertilizer) and T3 (excessive P fertilizer) treated soils. In addition, the bacterial phyla Proteobacteria, Chloroflexi, and Acidobacteria, and the fungal phyla Ascomycota and Basidiomycota dominated all the fertilized treatments. Soil total potassium (TK) concentration was the most important factor driving the variation in bacterial community structure under different fertilization regimes, while the major factors shaping fungal community structure were soil TN and NO3 –-N (nitrate N). These findings indicate that optimization of N and P application rates might result in variations in soil properties, which changed the microbial community structure in the present study.
Canadian Journal of Microbiology; https://doi.org/10.1139/cjm-2021-0053
Brucella abortus is a Gram-negative intracellular parasite bacteria causing serious health hazards in humans and animals. The type IV secretion system (T4SS), encoded by the virB promoter, has been identified as an important virulence factor for Brucella abortus, but the impact on Brucella abortus A19 remains unclear. In this study, the T4SS of Brucella abortus A19 was inactivated by deleting the virB promoter, resulting in a mutant strain A19ΔvirB. Real-time PCR and Western-blotting analysis demonstrated that T4SS-related proteins were not expressed after virB promoter deletion. Moreover, the survival rate of A19 in high salt and strong acidic environments was decreased after virB promoter deletion. Compared to the parental strain A19, the A19ΔvirB mutant strain showed reduced growth rate in TSB, decreased invasion ability to macrophages and dendritic cells, and reduced virulence of the mutant strain in macrophages, dendritic cells and mice. In addition, the A19ΔvirB mutant strain showed enhanced autophagy on macrophages and dendritic cells compared with A19, and the A19ΔvirB mutant strain was able to upregulate IL-6 and downregulate IL-10 in macrophages. These data help us to better understand the T4SS of the A19 vaccine strain and contribute to our efforts to improve Brucella vaccines.
Canadian Journal of Microbiology, Volume 67, pp 724-736; https://doi.org/10.1139/cjm-2020-0484
Lavender essential oil (LEO), a natural antimicrobial agent, is generally recognized as safe and effective in the inhibition of phytopathogenic fungi. Direct contact and fumigation (in vivo and in vitro) were used to study the fungistatic effect of LEO on Monilinia fructicola. Additionally, the effect on the ultrastructure of cells and the degree of destruction of the cell membrane of M. fructicola were revealed. In addition, the effects of LEO on the expression levels of apoptosis-related genes in M. fructicola cells were detected, and GC-MS was used to analyze the main components of LEO. LEO had a good inhibitory efficacy against M. fructicola in flat peaches, with almost complete growth inhibition at 800 μL/L. These effects were associated with the leakage of cytoplasmic contents, hyphal distortion, and spore disruption. Moreover, the expression of apoptosis RTG1 and RLM1 genes increased with LEO treatment. These results demonstrate that LEO can inhibit M. fructicola by inducing cytoplasmic membrane damage and cell apoptosis in fungi, and that the major ingredients of LEO are monoterpenes and sesquiterpenes, which are presumed to contribute to the inhibitory effects.
Canadian Journal of Microbiology, Volume 67, pp 687-702; https://doi.org/10.1139/cjm-2020-0572
Dengue is a vector-borne viral disease caused by the flavivirus dengue virus (DENV). Approximately 400 million cases and 22 000 deaths occur due to dengue worldwide each year. It has been reported in more than 100 countries in tropical and subtropical regions. A positive-stranded enveloped RNA virus (DENV) is principally transmitted by Aedes mosquitoes. It has four antigenically distinct serotypes, DENV-1 to DENV-4, with different genotypes and three structural proteins and seven non-structural proteins. Clinical symptoms of dengue range from mild fever to severe dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS), with thrombocytopenia, leucopenia, and increased vascular permeability. Although primary infection causes activation of immune responses against DENV serotypes, the severity of the disease is enhanced via heterotypic infection by various serotypes as well as antibody-dependent enhancement (ADE). The first licensed DENV vaccine was tetravalent CYD Denvaxia, but it has not been approved in all countries. The lack of a suitable animal model, a proper mechanistic study in pathogenesis, and ADE are the main hindrances in vaccine development. This review summarizes the current knowledge on DENV epidemiology, biology, and disease aetiology in the context of prevention and protection from dengue virus disease.
Canadian Journal of Microbiology; https://doi.org/10.1139/cjm-2021-0167
Photolyases (Phrs) are enzymes that utilize blue/ultraviolet (UV-A) region of light for repairing UV-induced cyclopyramidine dimer. We have studied Phr groups by bioinformatic analyses as well as active-site and structural modeling. The analysis of 238 amino acid sequences from 85 completely sequenced cyanobacterial genomes revealed five classes of Phrs, i.e., CPD Gr I, 6-4 Phrs/cryptochrome, Cry-DASH, Fe-S bacteria Phrs, and a group having fewer number of amino acids (276-385) in length. Distribution of Phr groups in cyanobacteria belonging to the order Synechococcales was found to be influenced by the habitats of the organisms. Class V Phrs were exclusively present in cyanobacteria. Unique motif and binding sites were reported in Group II and III. Fe-S protein binding site was only present in Group V. Active site residues and putative CPD/6-4pp binding residues are charged amino acids which were present on the surface of the proteins. Majority of hydrophilic amino acid residues were present on surface of Phrs. Sequence analysis confirmed the diverse nature of Phrs, though, sequence diversity does not affect their overall 3D structure. Protein-ligand interaction analysis identified novel CPD/6-4PP binding sites on Phrs. This structural information of Phrs can be used for the preparation of efficient Phr based formulations.
Canadian Journal of Microbiology; https://doi.org/10.1139/cjm-2021-0234
Antimicrobial resistance is one of the most serious threats to the medical sciences. The food supply is recognized as a potential source of resistant bacteria, leading to the development of surveillance programs targeting primarily poultry, pork and beef. These programs are limited in scope not only in the commodities tested, but also in the organisms targeted (Escherichia coli, Salmonella and Campylobacter); consequently, neither the breadth of food products available nor the organisms which may harbour clinically relevant and/or mobile resistance genes are identified. Furthermore, there is an inadequate understanding of how the international trade in food products contributes to the global dissemination of resistance. This is despite the recognized role of international travel in dissemination disseminating antimicrobial-resistant organisms (ARO), notably the New Delhi Metallo-betalactamase. An increasing number of studies describing ARO in a variety of imported foods will be summarized in this review.
Canadian Journal of Microbiology; https://doi.org/10.1139/cjm-2021-0211
Nowadays, resistance in pathogens against antibiotics is one of the most critical health-threatening problems in the world. Therefore, finding new treatment methods to be used as an alternative to antibiotics has become a priority for researchers. Like phages, certain products containing antimicrobial components such as molasses are widely used to eliminate resistant bacteria. Molasses has a strong antimicrobial effect on the bacterial cell, and this effect is thought to be due to the breakdown of the cytoplasmic cell membrane and cell proteins of the polyphenols in molasses. In the present study, phages-molasses interactions were investigated to examine the effects arising from concomitant use. It was found that molasses samples increased the size of phage plaques by up to 3-fold, and MIC and 1/2×MIC concentration of molasses increased the burst size of phages. Although no synergistic effect was found between the phage and the molasses, the antimicrobial activities of the components and the effect of molasses on phage activity were demonstrated.
Canadian Journal of Microbiology; https://doi.org/10.1139/cjm-2021-0110
Hyaluronic acid is a high molecular weight polysaccharide that is widely distributed in animal tissues. Bacterial hyaluronidases degrade hyaluronic acid as secreted enzymes and have been shown to contribute to infection. Staphylococcus aureus UAMS-1 is a clinical isolate that codes for two hyaluronidases (hysA1 and hysA2). Previous research has shown the presence of a full-length HysA1 protein from the S. aureus UAMS-1 strain with no evidence of enzymatic activity. A single base change resulting in an E480G amino acid change was identified in the S. aureus UAMS-1 hysA1 gene when compared to the S. aureus Sanger 252 hysA1 gene. A plasmid copy of the S. aureus Sanger 252 hysA1 gene transduced into a hysA2 deletion mutant strain of S. aureus UAMS-1 restored near wild type levels of enzymatic activity. Homology modeling and structural analysis suggested that Glu-480 in the HysA1 is critically responsible for maintaining the structural and functional ensemble of the catalytic and tunnel-forming residues, which are essential for enzyme activity. A high degree of relatedness among several Gram-positive bacterial hyaluronidases indicate the loss of enzymatic activity of HysA1 in the S. aureus UAMS-1 strain is most likely caused by the mutation identified in our study.