Canadian journal of microbiology最新文献

Acinetobacter baumannii is an opportunistic pathogen that is often studied in commonly used rich media in laboratories worldwide. Due to the metabolic versatility of A. baumannii, it can be cultured in different growth mediums; however, this can lead to genotypic and phenotypic variations. In this study, we compared phenotypic and transcriptomic changes in A. baumannii ATCC17978-VU cultured in M9 minimal media supplemented with 20 mmol/L sodium succinate and rich lysogeny broth media. Phenotypically, growth was significantly slowed, virulence in Galleria mellonella was attenuated, and susceptibility to a variety of antibiotic classes was reduced when A. baumannii ATCC17978-VU was grown in minimal media versus rich media. Transcriptomic analysis showed differential regulation of >700 genes-including those associated with energy production and ribosomal function-when the two growth conditions were compared, with the majority of the upregulated genes seen in minimal media of unknown function. This study showed that culture media has a profound effect on the phenotype and cellular workings of a bacteria, highlighting the need for more studies of pathogens like A. baumannii ATCC17978-VU in minimal media.

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, -54.22, and -41.86 kcal/mol, which further corroborated the strong binding. During 100 ns 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 root-mean-square deviation values of the ligand-protein complex are within the appropriate range of less than 5 Å. Absorption, Distribution, Metabolism, Excretion, and Toxicity 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.

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.

Lake Guamuez is the second largest lake in Colombia and economically supports hundreds of families in the area. The main activities carried out in the region have focused on tourism, agriculture, livestock, and rainbow trout production; however, these activities have been associated with contamination of the lake. This research aimed to evaluate the water quality of Lake Guamuez using somatic coliphages (SCs) as bioindicators. For this purpose, periodic sampling was carried out for 6 months at nine strategic points of the lake. For the detection of SCs, the method described in 9211 D of the Standard Methods for the Examination of Water and Wastewater was used. The genomic variability and presence of virulence genes in the isolated SCs were determined. Water contamination in the lake is evident, and the SCs titer is greater in areas with a high flow of anthropogenic activities. An important degree of genetic diversity and a high prevalence of virulence genes could be observed among the SCs analyzed. The results when compared with guidelines and water quality standards from various countries showed concentrations of SCs higher than those allowed. The high prevalence of gastrointestinal diseases in the region suggests a link to water contamination.

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 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.

Bacteria encounter various stressful conditions within a variety of dynamic environments, which they must overcome for survival. One way they achieve this is by developing phenotypic heterogeneity to introduce diversity within their population. Such distinct subpopulations can arise through endogenous fluctuations in regulatory components, wherein bacteria can express diverse phenotypes and switch between them, sometimes in a heritable and reversible manner. This switching may also lead to antigenic variation, enabling pathogenic bacteria to evade the host immune response. Therefore, phenotypic heterogeneity plays a significant role in microbial pathogenesis, immune evasion, antibiotic resistance, host niche tissue establishment, and environmental persistence. This heterogeneity can result from stochastic and responsive switches, as well as various genetic and epigenetic mechanisms. The development of phenotypic heterogeneity may create clonal populations that differ in their level of virulence, contribute to the formation of biofilms, and allow for antibiotic persistence within select morphological variants. This review delves into the current understanding of the molecular switching mechanisms underlying phenotypic heterogeneity, highlighting their roles in establishing infections caused by select bacterial pathogens.

Highly pathogenic avian influenza (HPAI) H5N1 has caused the deaths of more than 100 million birds since 2021, and human cases since 1997 have been associated with significant morbidity and mortality. Given recent detections of HPAI H5N1 in dairy cattle and H5N1 RNA detections in pasteurized retail milk in the United States, we established the pan-Canadian Milk Network in April 2024. Through our network of collaborators from across Canada, retail milk was procured longitudinally, approximately every 2 weeks, and sent to a central laboratory to test for the presence of influenza A virus RNA. Between 29 April and 17 July 2024, we tested 109 retail milk samples from all 10 Canadian provinces (NL, NS, PEI, NB, QC, ON, MB, SK, AB, and BC). All samples tested negative for influenza A virus RNA. This nationwide initiative was established for rapid retail milk screening as per the earliest reports of similar undertakings in the United States. Our independent testing results have aligned with reporting from federal retail milk testing initiatives. Despite no known HPAI infections of dairy cattle in Canada to date, H5N1 poses a significant threat to the health of both humans and other animals. By performing routine surveillance of retail milk on a national scale, we have shown that academic networks and initiatives can rapidly establish nationwide emerging infectious disease surveillance that is cost-effective, standardized, scalable, and easily accessible. Our network can serve as an early detection system to help inform containment and mitigation activities if positive samples are identified and can be readily reactivated should HPAI H5N1 or other emerging zoonotic viruses be identified in agricultural or livestock settings, including Canadian dairy cattle.

Many arthropods, including economically important pests of stored grains, host intracellular bacterial symbionts. These symbionts can have diverse impacts on host morphology, stress tolerance, and reproductive success. The ability to rapidly determine the infection status of host insects and the identity of intracellular symbionts, if present, is vital to understanding the biology and ecology of these organisms. We used a microbiome profiling method based on amplicon sequencing to rapidly screen 35 captive insect colonies. This method effectively revealed single and mixed infections by intracellular bacterial symbionts, as well as the presence or absence of a dominant symbiont, when that was the case. Because no a priori decisions are required about probable host-symbiont pairing, this method is able to quickly identify novel associations. This work highlights the frequency of endosymbionts, indicates some unexpected pairings that should be investigated further, such as dominant bacterial taxa that are not among the canonical genera of endosymbionts, and reveals different colonies of the same host insect species that differ in the presence and identity of endosymbiotic bacteria.