Microbiology-Sgm最新文献

Candida albicans is an opportunistic fungal pathogen associated with superficial and systemic infections in humans. Azole antifungal resistance in C. albicans is of clinical concern, and both oral and systemic Candida infections can be difficult to treat due to the lack of alternative antifungal drugs. Expression of a hyperactive form of the transcription factor Tac1 is a major contributor to azole resistance in C. albicans isolates resulting in the increased expression of the azole efflux pump Cdr1. In this study, we investigated whether the Mediator tail component Med2, encoded by the expanded (n=14) TLO gene family of C. albicans, was required for Tac1 activity. A homozygous TAC1-5 gain-of-function point mutation was introduced into WT, tloΔ and med3Δ strains of C. albicans which enables them to express hyperactive Tac1. qRT-PCR analysis revealed that tloΔ-TAC1-5 had reduced basal and fluphenazine-induced CDR1 expression relative to WT-TAC1-5 strains and exhibited reduced levels of resistance to fluconazole and terbinafine. Individual copies of representatives from each of the alpha, beta and gamma TLO clades were reintroduced into tloΔ-TAC1-5 to investigate their ability to restore Tac1-activated resistance. These studies show that alpha and beta TLO genes could restore fluconazole resistance in the tloΔ-TAC1-5 background, whereas gamma clade genes did not result in any detectable phenotypic complementation. Transcript profiling showed that reintroduction of TLOα1 led to increased expression of TAC1-5-activated genes such as CDR1. Further analysis using ChIP-qPCR revealed that Tloα1 localizes to the drug response element which is the site where Tac1 binds to the CDR1 promoter. These data have identified that the TLO gene family is required for the expression of Tac1-mediated fluconazole resistance. However, this effect is confined to members of the alpha and beta, but not the gamma, TLO clades.

Microbial surfactants (biosurfactants) are low-molecular-weight amphiphilic secondary metabolites synthesized by a wide range of micro-organisms, including bacteria, yeasts and fungi. These compounds reduce surface and interfacial tension, promote emulsification and self-assemble into supramolecular structures such as micelles. Their remarkable structural diversity reflects the metabolic complexity of their microbial producers. In this primer, we outline shared features across biosurfactant-producing organisms, focusing on biosynthetic pathways, biological functions and regulatory mechanisms. The study of biosurfactants lies at the intersection of ecological, biotechnological and medical research, offering valuable insights into microbial ecology and promising avenues for sustainable innovation.

Enterococcus faecalis encodes three putative Escherichia coli β-ketoacyl-acyl carrier protein (ACP) reductases (FabG). The fabG1 gene is located within the operon that encodes most of the fatty acid synthesis genes, while the putative fabG2 and fabG3 genes are located elsewhere on the chromosome. The genes were tested for the ability to complement the growth of an E. coli fabG(Ts) strain at the non-permissive temperature. Of the three genes, only E. faecalis FabG1 restored growth at high temperature. Moreover, deletion of the E. faecalis fabG1 gene resulted in an auxotrophic strain that required oleic acid for growth, arguing that it encodes the only functional β-ketoacyl-ACP reductase. Growth of this strain in the absence of fatty acid was restored by plasmid-borne fabG1, but not by plasmids encoding either fabG2 or fabG3. Although E. faecalis fabG2 has a putative binding site for the FabT transcription factor at the 5' end of the coding region, expression of a transcriptional fusion with β-galactosidase was unaffected by deletion of fabT or by fatty acid supplementation.

Fungi are ubiquitous micro-organisms involved in various environmental processes, with a particularly important role in the transformation of metals and minerals, bioremediation and biomining. Filamentous fungus Phycomyces blakesleeanus is an interesting model for investigating the interaction of fungi with various ecological factors, such as heavy metals, due to the ease of its cultivation and fast growth. The present study deals with the interaction of increasing vanadate [V(V)] concentrations with the mycelium of P. blakesleeanus in three distinct growth phases: mid-exponential, late exponential and stationary phase. Mid- and late-exponential phase mycelium had a V content of nearly 1% after 24 h incubation with 10 mM V(V), and the uptake of V(V) was accompanied by increased phosphorus uptake with both 5 and 10 mM V(V). Fourier Transform Infrared spectroscopy showed the increase of lipid portion in biomass compared to proteins and carbohydrates mainly with ageing, but also with vanadate treatment. P. blakesleeanus is tolerant to high V(V) concentrations, and this study suggests its potential as V accumulator. In addition, the increase in lipid content calls for a closer examination of lipid content and fatty acid composition after V(V) treatment and determination of their potential industrial utilization.

The pathogenesis of cholestatic liver disease (CLD) is unknown, but the influence of gut microbiota and inflammation cannot be ignored. In this study, we attempted to provide theoretical insights for the diagnosis and treatment of CLD in children by analysing the association between gut microbiota, IL-17 levels and clinical characteristics. This research involved 21 children diagnosed with CLD and 11 healthy controls. Blood and faecal samples were collected from these participants. Blood samples underwent analysis for clinical indicators and IL-17 concentrations. Gut microbiota was examined through 16S rRNA gene sequencing for identification and functional prediction. A positive correlation between IL-17 levels and clinical parameters (total bile acids, alanine aminotransferase, aspartate aminotransferase and triglycerides) in children with CLD was observed. Notably, children with CLD exhibited reduced diversity and disturbances in gut microbiota, highlighted by a severe decrease of Bacteroidota (genus Bacteroides). Moreover, increased relative abundance of secondary bile acid-promoting (e.g. Clostridium, Enterococcus and Bifidobacterium) and deleterious (e.g. Escherichia-Shigella and Streptococcus) flora in the intestinal flora of children with CLD was positively correlated with IL-17, leading to increased inflammation and CLD aggravation. Functional predictions of gut microbiota revealed higher concentrations of l-asparagine transporter, ABC-type polar amino acid transport system and glycolysis II (from fructose 6-phosphate) functions, while the function of the Na⁺-driven multidrug efflux pump was decreased. In conclusion, children suffering from CLD exhibit significant gut microbiota disturbances, particularly a severe decrease in Bacteroidota (genus Bacteroides). Dysbiosis of the gut microbiota and elevated levels of IL-17 mutually reinforce each other, together mediating the onset and progression of CLD.

Staphylococcus aureus has evolved a complex regulatory network to coordinate expression of virulence factors, including cytolytic toxins, with host environmental signals. Central to this network are two-component systems (TCSs), in which a histidine kinase senses an external signal and activates a response regulator via phosphorylation, leading to changes in gene expression. Using a comprehensive screen of transposon mutants in each of the non-essential histidine kinase and response regulator genes in S. aureus, we demonstrate that 11 of these 16 systems regulate cytotoxicity. Further characterization of the phosphate-sensing PhoPR system revealed that PhoP affects cytotoxicity in a manner mediated through the Agr quorum-sensing system. Notably, we found that unphosphorylated PhoP is an activator of Agr activity, whilst phosphorylated PhoP also acts as a weak activator of Agr activity in high-phosphate environments but as a repressor in low-phosphate environments. Furthermore, overexpression of PhoP resulted in upregulation of α-type phenol-soluble modulins, which may also contribute to the cytotoxicity phenotype observed in the phoP mutant. Overall, we have demonstrated that phosphate sensing through PhoPR is a novel regulator of cytotoxicity in S. aureus. Moreover, our study challenges the canonical model of TCSs as simple on/off systems and highlights the importance of unphosphorylated response regulators in gene regulation.

The emergence of a new clade of emm89 group A Streptococcus (GAS) (clade 3) has been described in several countries. Strains in this clade have been reported to have genomic characteristics that lead to increased expression of virulence factors and may confer a selective advantage over previous emm89 strains. To investigate whether clade 3 GAS is present in the emm89 GAS population of Queensland, Australia, all emm89 GAS isolates received by the Queensland Public Health Microbiology Reference Laboratory since emm typing began in the early 2000s underwent genomic sequencing and analysis. Analysis of sequences from 293 emm89 GAS isolates demonstrated the presence of distinct genomic groups in the Queensland emm89 GAS population. Unlike emm89 GAS populations described in the UK and USA, which were mostly ST101 and ST407, there were a relatively high number of ST142 and ST812 strains in the Queensland emm89 GAS population. However, the majority of Queensland isolates belonged to clade 3, with 80% (n=233) of emm89 GAS isolated from 2006 onwards belonging to this clade. All Queensland clade 3 isolates had the reported genomic features associated with higher virulence potential including increased streptolysin O production and an acapsular phenotype. Clade 3, which has emerged to become the dominant clade of emm89 GAS in Europe and the USA, is now also the dominant clade in Queensland.

Common beans (Phaseolus vulgaris L) are an important staple crop valued for their high protein content and dietary benefits. However, Fusarium wilt, caused by Fusarium solani, is responsible for up to an 84% yield loss in bean production. This study aimed to isolate and evaluate novel Pseudomonas fluorescens from Lake Bogoria as potential biocontrol agents against F. solani. Using serial dilution, 30 bacterial isolates were obtained; 10 showed varied mycelial inhibition rates (5.95-42.86%) through dual culture and confrontation assays. Molecular identification using 16S rDNA confirmed that two isolates were Pseudomonas fluorescens strains. Antibiosis gene screening revealed the presence of 2,4-diacetylphloroglucinol, pyrrolnitrin, pyoluteorin and hydrogen cyanide. Enzyme assays demonstrated chitinase (1.33-3,160 U ml^-1) and chitosanase (12.67-29.00 mm) production, indicating antifungal capabilities. In vivo pot experiments with isolate TW17⁺ showed reduced wilt symptoms <20.0% and disease incidence (8.0-35.0%). These findings highlight the potential of soda lake-derived Pseudomonas fluorescens as an effective biocontrol agent against F. solani, with additional benefits for common bean growth and yield improvement.

Competition assays are a mainstay of modern microbiology, offering a simple and cost-effective means to quantify microbe-microbe interactions in vitro. Here, we demonstrate a key weakness of this method that arises when competing microbes interact via toxins, such as those secreted via the type VI secretion system (T6SS). Time-lapse microscopy reveals that T6SS-armed Acinetobacter baylyi bacteria can maintain lethal T6SS activity against E. coli target cells, even under selective conditions intended to eliminate A. baylyi. Further, this residual killing creates a density- and T6SS-dependent bias in the apparent recovery of E. coli, leading to a misreporting of competition outcomes where target survival is low. We also show that incubating A. baylyi/E. coli co-cultures in liquid antibiotic prior to selective plating can substantially correct this bias. Our findings demonstrate the need for caution when using selective plating as part of T6SS competition assays, or assays involving other toxin-producing bacteria.

Chronic rhinosinusitis (CRS) is a prevalent and life-altering disease characterized by the persistent inflammation of the sinuses lasting longer than 3 months. Pseudomonas aeruginosa (PA) is a prominent biofilm-forming bacterium that colonizes the sinuses of up to 9% of CRS patients. PA in biofilm exhibits a great resistance to antibiotics and has proven difficult to remove from the sinus mucosa of CRS patients. Influenza A virus (IAV) is the second most common virus detected colonizing CRS patients' sinuses, with previous studies finding that IAV-induced inflammation of human cells causes the dispersal of bacteria encased in biofilms, leading to increased disease exacerbations. Yet, the two pathogens and the effect that co-infection with them has on primary human nasal epithelial cells (HNECs) have to be assessed. In this study, we show that co-infection of HNECs with both clinical and laboratory isolates of PA and with IAV causes no significant change in PA biofilm biomass and no significant change in the production of PA virulence factors. We also show that co-infected HNECs exhibit lower IL-6 response when compared to HNECs infected with IAV alone, suggesting a novel finding where PA is dampening IL-6 response once co-infection occurs.