Canadian journal of microbiology最新文献

The objective of this study was to compare chlorhexidine digluconate and other antibiotics susceptibility of 4 species in Acinetobacter baumannii complex, and further investigate the 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%. A. 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 qacEΔ1, 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 ST 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.

Conjugation is a complex phenomenon involving multiple plasmid, bacterial, and environmental factors. Here we describe an IncI1 plasmid encoding multidrug antibiotic resistance to aminoglycosides, sulfonamides, and third generation cephalosporins. This plasmid is widespread geographically and among One Health animal, human, and environmental sectors. We present data on the transmissibility of this plasmid from S. enterica ser. Kentucky into forty strains of S. enterica (10 strains each from serovars Enteritidis, Heidelberg, Infantis, and Typhimurium). Thirty-seven out of forty strains were able to take up the plasmid. Rates of conjugation were variable between strains ranging from 10^-8 to 10^-4. Overall, serovars Enteritidis and Typhimurium demonstrated the highest rates of conjugation, followed by Heidelberg, and then Infantis. No relationships were observed between the recipient cell surface and rate of conjugation. Recipient cell numbers correlated positively with conjugation rate and strains with high conjugation rates had marginally but significantly higher growth parameters compared to strains that took up the plasmid at lower frequencies. Environmental conditions known to impact cell growth such as temperature, nutrient availability, and the presence of antibiotics had a modulating effect on conjugation. Collectively, these results will further understanding of plasmid transmission dynamics in Salmonella which is a critical first step towards the development of mitigation strategies.

Leptographium wingfieldii is a fungal associate of Tomicus piniperda (the pine shoot beetle) and pathogen of pines and this species is an agent of blue stain in sapwood on infected trees. This fungus was first reported from Europe and has been recently introduced to Canadian forests. Ten new mitogenomes have been sequenced and characterized, including seven strains of L. wingfieldii, two strains of L. procerum and one strain of L. terebrantis. The data were combined with other members of the Ophiostomatales collected from NCBI to gain more insight into the genetic diversity, evolution, and systematics of these fungi. The size of the studied mitogenomes of Leptographium species ranged from 41 kb to 126 kb with the number of potential mobile introns embedded within these mitogenomes ranging from 13 to 45. These data show that introns generate genetic diversity and confirms the contribution of mobile introns in genome expansion in Ophiostomatales fungi. This study also uncovered complex intron arrangements (twintrons) suggesting the potential of mobile introns generating complex ribozymes that may have implications in gene regulation.

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.

Klebsiella pneumoniae is a ubiquitous opportunistic pathogen of the family Enterobacteriaceae. K. pneumoniae is a member of the ESKAPEE pathogens (Enterococcus faecium, Staphylococcus aureus, K. pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp., and Escherichia coli), a group of bacteria that cause nosocomial infections and are able to resist killing by commonly relied upon antimicrobial agents. The acquisition of antimicrobial resistance (AMR) genes is increasing among community and clinical isolates of K. pneumoniae, making K. pneumoniae a rising threat to human health. In addition to the increase in AMR, K. pneumoniae is also thought to disseminate AMR genes to other bacterial species. In this review, the known mechanisms of K. pneumoniae AMR will be described and the current state of AMR K. pneumoniae within Canada will be discussed, including the impact of the coronavirus disease-2019 pandemic, current perspectives, and outlook for the future.

Plant growth promotion by Pseudomonas sp. 31-12 incorporated into a lettuce seed pelleting matrix was studied. We examined (1) the effect of five rhizosphere derived bacterial strains on green oak lettuce (Lactuca sativa L.) seed germination, root and shoot growth, as a strain selection step for seed coating and seed pelletizing studies, (2) population stability of Pseudomonas sp. 31-12 incorporated into a pelleting matrix on lettuce seed stored three months at 4 °C, and (3) lettuce growth promotion in the laboratory and greenhouse by Pseudomonas sp. 31-12 coated and pelletized seed. A spontaneous streptomycin mutant of Pseudomonas sp. 31-12 (str) was used to determine population size on seed and roots of 15- and 30-day-old lettuce. The population of Pseudomonas sp. 31-12str on coated and pelleted seed decreased from 10⁴ cfu/seed to 10³ cfu/seed after 3 months storage at 4 °C. However, the population exceeded 10⁴ cfu/g root dry mass and 10⁵/g root dry mass after 15 days and 30 days in the greenhouse. Leaf fresh mass was significantly increased (P ≤ 0.05) with Pseudomonas sp. 31-12 seed treatment as compared to noninoculated seed. In conclusion, pelletized lettuce seed with Pseudomonas sp. 31-12 promoted growth and yield in the greenhouse.

Frankia represent a unique group of filamentous, sporangia-forming bacteria, renowned for their exceptional capacity to establish symbiotic partnerships with actinorhizal plants. The objective of this paper is to offer quantitative insights into the current state of frankia research and its future potential. A comprehensive bibliometric analysis covering the years 2000-2022 was conducted using Scopus and SciVal. A steady increase in both annual publication and international collaboration has been observed, particularly since 2013. Research performance metrics for the last 5 years (2018-2022) indicate China and India as leaders with high Field-Weighted Citation Impact scores. This analysis highlighted prominent authors, research groups, and the evolving research landscape, suggesting an increasing focus on molecular and genomic aspects. The genomic era has transformed our understanding of frankia biology, highlighting their significance in diverse ecological and agricultural contexts. This study comprehensively maps the evolving landscape of frankia research, emphasizing key milestones that have catalysed international interest in frankia-actinorhizal research, expanding our perception of frankia's capabilities beyond its traditional symbiotic role. As research in this field progresses, a deeper comprehension of frankia-plant interactions, symbiotic signalling, and the intricacies of metabolic pathways holds the promise of revealing innovative techniques for optimizing nitrogen fixation and broadening the spectrum of host plants.

The principal methods to maintain soil fertility in Sahel soils are largely allowing fields to go fallow and manure addition. These methods are not currently sufficient to improve soil fertility. To promote biological amendments, we aimed to understand the plant-growth promoting traits of various soil microbial isolates. The soils collected in different areas in Senegal exhibited a similar eDNA profile of bacteria; the dominant microbes were Firmicutes, followed by Proteobacteria and Actinobacteria. Of 17 isolates identified and tested, the vast majority solubilized rock phosphate and a large number grew on culture medium containing 6% salt, but very few degraded starches or hydrolysed carboxymethyl cellulose or produced siderophores. Upon single inoculation, Peribacillus asahii RC16 and Dietzia cinnamea 55 significantly increased pearl millet growth and yield parameters. For cowpea, plant shoot length was significantly increased by Pseudarthrobacter phenanthrenivorans MKAG7 co-inoculated with Bradyrhizobium elkanii 20TpCR5, and nearly all rhizobacteria tested significantly improved cowpea dry weight and pod weight. Additionally, the double inoculation of Dietzia cinnamea 55 and MKAG7 significantly increased shoot length, dry weight, and seed head weight of pearl millet. These isolates are promising inoculants because they are ecologically-friendly, cost-effective, sustainable, and have fewer negative effects on the soil and its inhabitants.

The pathogenic Pseudomonas aeruginosa utilizes a quorum-sensing pathway for biofilm formation. The quorum-sensing proteins LasI and LasR of the Las system, alongside the swarming motility protein BswR, play a crucial role in the biofilm-mediated antibiotic resistance phenomenon. In this in-silico study, LasI, LasR, and BswR were the prime targets for binding studies by promising drug candidates like linalool, ferutinin, citronellal, and carvacrol. These monoterpenoid compounds are carefully considered for this study due to their reported anti-microbial activity. Among all, carvacrol exhibited the highest binding energies with LasI (-5.932 kcal/mol), LasR (-7.469 kcal/mol), and BswR (-4.42 kcal/mol). Furthermore, the MMGBSA scores between carvacrol and LasI, LasR, and BswR individually are -33.14 kcal/mol, -54.22 kcal/mol, and -41.86 kcal/mol, which further corroborated the strong binding. During 100ns of simulation, the ligand binds to the active sites of these proteins through the H-bonds at Ile107 of LasI, Tyr47 of LasR, and Leu57 of BswR. In addition, the RMSD values of the ligand-protein complex are within the appropriate range of less than 5Å. ADME/T analysis confirmed that carvacrol has the most negligible toxicity to mammalian cells. Hence, this finding is the first report to show that carvacrol can inhibit the Pseudomonas aeruginosa biofilms.