Journal of Applied Microbiology最新文献

Aim: Pseudomonas aeruginosa employs the quorum sensing (QS) system, a sophisticated cell-to-cell communication mechanism, to modulate the synthesis and secretion of a range of virulence factors, which contribute to the establishment of acute or chronic infections in hosts. This study seeks to attenuate the virulence of P. aeruginosa by inhibiting the QS system, thereby reducing its pathogenicity as a promising alternative to traditional antibiotics.

Methods and results: Two compounds with an amino-substituted diphenyl fumaramide core, N1-(4-bromophenyl)-N4-(4'-oxo-3',4'-dihydro-1'H-spiro [cyclopentane-1,2'-quinazolin]-6'-yl) fumaramide (10D) and N1-(3-chloro-4-fluorophenyl)-N4-(4-oxo-3,4,4',5'-tetrahydro-1H,2'H-spiro [quinazoline-2,3'-thiophen]-6-yl) fumaramide (12A), were identified through in-silico screening. The QS inhibitory potential of both compounds was explored in vitro and in vivo. In in vitro experiments, neither compound exhibited bactericidal effects but significantly inhibited the production of QS-regulated extracellular protease and pyocyanin. Quantitative PCR analysis revealed that QS-activated genes and downstream virulence genes were transcriptionally suppressed by 10D or 12A. Molecular docking and molecular dynamics simulations predicted stable interactions between these compounds and the key QS regulators LasR and PqsR. When combined with polymyxin B, kanamycin, and levofloxacin, 10D and 12A exhibited synergistic antibacterial activity. Furthermore, compounds 10D and 12A significantly improved the survival of mice challenged with P. aeruginosa and effectively reduced the bacterial load in the lungs.

Conclusion: This study indicates that 10D and 12A possess considerable QS inhibitory potential, effectively attenuating the pathogenicity of P. aeruginosa. Moreover, the study offers structural insights and methodological guidance for the advancement of anti-virulence drug development.

Aims: In the present study, we tested whether terrestrially derived humic substances (HS) could mitigate the adverse effects of elevated temperature and ultraviolet B (UVB) radiation on the bacterial communities of two hard corals (Montipora digitata and M. capricornis), one soft coral (Sarcophyton glaucum), sediment and water. We also examined the impact of temperature, UVB radiation, and HS supplementation on coral photosynthetic activity, a proxy for coral bleaching.

Methods and results: We performed a multifactorial experiment using a randomized-controlled microcosm setup. Coral photosynthetic efficiency was measured in vivo using a pulse amplitude modulation fluorometer. Bacterial communities were analyzed using 16S rRNA gene sequencing. Corals in HS-supplemented microcosms had significantly higher photosynthetic activities than those in microcosms subjected to elevated temperature and UVB radiation. Additionally, HS supplementation significantly influenced the composition of sediment, water, and host-associated bacterial communities. Reef organisms in HS supplemented microcosms contained distinct bacterial communities enriched with groups of potentially beneficial bacteria. In the hard coral M. digitata, we observed an interactive effect of HS supplementation, UVB radiation, and temperature.

Conclusion: Our findings indicate that HS significantly modulates coral reef bacterial communities and support the hypothesis that these substances contribute to improved reef resistance to the adverse effects of elevated temperature and UVB radiation.

Aims: Flammulina filiformis, a widely cultivated edible fungus, frequently suffers from strain degeneration, leading to reduce yield and quality, and causing significant economic losses in large-scale production. This study aimed to better understand degeneration mechanisms and to develop an assay for predicting degeneration.

Methods and results: This study investigates strain degeneration by comparing a cultivated strain (F1) and its subcultured derivative (F7). Although both strains display similar mycelial growth, F7 shows impaired fruiting body production, indicating that degeneration occurs prior to visible changes in mycelial growth. To uncover the molecular mechanisms underlying degeneration, transcriptome analysis was carried out. A total of 352 down-regulated and 280 up-regulated differentially expressed genes (DEGs) were identified in F7 compared to F1. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed significant enrichment of DEGs in functional categories related to oxidoreductase activities and peroxisome pathway. Quantitative PCR further validated the regulation of certain DEGs associated with these enriched functions. A stress tolerance assay was developed to detect degeneration in strains with unchanged mycelial growth but reduced fruiting body production.

Conclusions: Results suggested that strain degeneration in F. filiformis is closely linked to oxidative stress regulation and occurs prior to observable mycelial impairment.

Aims: To describe the analysis, epidemiology, and control of six contemporaneous and linked outbreaks of Salmonella enterica subsp. enterica serovar Infantis on British broiler farms. Salmonella Infantis is a potentially multidrug-resistant foodborne zoonosis and can persistently colonize poultry flocks and farms.

Methods and results: Routine monitoring initially identified the organism, which was tracked to six farms associated with a single company. Extensive, repeat sampling identified widespread and, in some cases, persistent contamination. Salmonella Infantis was also isolated from three associated processing factories and catching crew equipment, but not from associated hatcheries and feed mills. Whole genome sequencing and resistance phenotyping revealed one strain was present in the processing plants and on five farms. However, on one of those farms, several highly genetically distinct strains were also detected, including one also found in one of the processing plants. The sixth farm had a strain that was genetically unrelated to strains collected from the other premises and which exhibited an extended spectrum beta-lactamase phenotype. Cleaning and disinfection were enhanced, and the organism was eventually cleared from all farms.

Conclusions: There were multiple incursions of varied strains, with a possible link to processing factories. Elimination of S. Infantis from premises can be challenging but achievable.

Background: Stenotrophomonas maltophilia is the species most frequently identified by clinical microbiology laboratories due to its presence in the main identification systems databases. Phenotypic identification methods are widely used in laboratories, and the misidentification of Stenotrophomonas spp. is highly probable due to the presence of cryptic species. Our aim was to confirm the identity of five cefiderocol-resistant Stenotrophomonas species, initially identified as S. maltophilia, using genome analysis tools, performing comparative and functional analyses of these clinical strains associated with infectious processes.

Methods: Identifications were performed using: Average Nucleotide Identity, Average Amino Acid Identity, and in silico DNA-DNA hybridization. Virulence factors, resistance mechanisms, prophages, CRISPR elements, and metabolism elements were identified and annotated.

Results: We confirmed the identity of the strains C960 and C2866 as Stenotrophomonas geniculata, and of strain C1657 as Stenotrophomonas indicatrix. The species designation parameters obtained indicated that the strains C4297 and C2852 are novel species. In comparison with the hypothetical proteome of the S. maltophilia complex species analyzed, elements associated with amino acid metabolism, DNA/RNA processing and repair, envelope biogenesis, and intracellular transport are predominant. Elements probably associated with antibiotic resistance, such as efflux pumps, aminoglycoside transferases, and phosphoethanolamine transferases, were identified, and the presence of genes related to capsule formation, iron acquisition, and intracellular survival probably contributes to virulence.

Conclusions: This is the first report of S. geniculata and S. indicatrix as human pathogens. Besides, we proposed two novel species members of Smc: Stenotrophomonas veracruzanensis sp. nov. and Stenotrophomonas mexicanensis sp. nov.

Aims: The urgent search for new natural bioactive compounds is crucial to address growing clinical demands. With this perspective, this paper focuses on isolating and bioprospecting fungal endophytes from some plant species in a local forest in Wrocław, Poland.

Methods and results: Forty-three fungal endophytes were isolated and their extracts were tested for inhibitory potential against monoamine oxidase A (MAO-A), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and for peroxisome proliferator-activated receptor gamma (PPAR-γ) agonists. Six promising strains after screening were identified to possess all these activities. These strains and their respective plant hosts were Sphaeropsis sapinea BUK-L2 (Fagus sylvatica), Coniochaeta velutina SW-B (Picea abies), Epicoccum nigrum COR-B (Corylus avellana), Paraphaeosphaeria verruculosa JAR-B (Sorbus aucuparia), Umbelopsis isabellina COR-L1 (Corylus avellana), and Epicoccum mezzettii QR-B (Quercus robur). Moreover, gamma irradiation at several doses (Gy) was separately applied to the fungal cultures to study their enhancement effects on the recorded activities. Finally, compounds of active bands from preparative thin-layer chromatography of the two promising strains (Coniochaeta velutina SW-B and Epicoccum nigrum COR-B), were identified by GC-MS (Gas chromatography-mass spectrometry).

Conclusions: The present study is the first report on bioprospecting endophytic fungi of forest plants for the aforementioned activities.

Aims: Ultraviolet radiation (UVR) interferes with aspects of life on Earth. It is necessary for the synthesis of important molecules, as vitamin D, but it is harmful to organisms leading to photoaging and skin cancer. Artificial sunscreens prevent these harmful effects, but may be carcinogenic and neurotoxic; also they accumulate in the aquatic ecosystem, harming the environment and leading to coral bleaching. Most artificial sunscreens commercialized are fossil fuel derived and produced by the petrochemical industry. As society turns to bioeconomy, these artificial sunscreens may be substituted by sustainable ones. Algae, cyanobacteria and fungi produce mycosporines and mycosporine-like aminoacids, which absorb UV radiation and dissipate it as heat. They are a natural source of sunscreen with low or no toxicity and can be produced by biotechnological means; therefore, the aim of this study is to search for mycosporine biosynthesis in yeast from an extreme environment.

Methods and results: chromatographic and spectroscopic data analyses demonstrated for the first time an isolate of Naganishia friedmannii, collected from a site with high UVR incidence, is able to produce mycosporine-glutaminol-glucoside (MGG) and its likely diastereoisomer, when exposed to PAR-UVR light. A biosynthetic gene cluster was identified in the N. friedmannii genome and shown to be induced in response to UVR by Real-Time PCR. Phenotypic characterization suggests N. friedmannii is non-pathogenic yeast that tolerates UVC radiation and other stresses.

Conclusions: these features make N. friedmannii suitable for biotechnological applications, adding value to yeast mycosporines as an additive for economically viable, sustainable and environmentally friendly sunscreens.

Aim: The dietary proteins in poultry feeds, including the polypeptide chain size, influence gut microbial composition and function. This study assessed the microbial preference for peptide size using the same protein source in three polypeptide forms.

Methods: We investigated the effects of diphenyliodonium chloride (DIC) on poultry cecal microbiota inoculated with C. jejuni and supplemented with various casein hydrolysates (intact casein, enzyme hydrolysate, acid hydrolysate, and a mix of all three) using an in vitro cecal model. The incubation occurred over 18 hours at 42°C under microaerophilic conditions. We hypothesized a decrease in C. jejuni abundance by limiting nitrogenous metabolites while promoting the growth of protein fermentative bacteria. Additionally, we speculated that the response to DIC would vary with different polypeptides. Genomic DNA was extracted, amplified, and sequenced on an Illumina MiSeq platform.

Results: Analysis within QIIME2-2021.11 showed that DIC treatments did not significantly affect C. jejuni abundance but drastically decreased Enterobacteriaceae abundance (ANCOM, P < 0.05). DIC-treated groups exhibited a more stable community structure, especially in the peptide-amended group. Microbial interactions likely aided C. jejuni survival in DIC groups with casein hydrolysates. Methanocorpusculum, Phascolarctobacterium, and Campylobacter formed a core microbial community in both DIC-treated and non-treated groups. DIC altered co-occurrence patterns among core members and differentiated taxa in abundance in acid and peptide-DIC treated groups, changing negative relationships to positive ones (Spearman's Correlation, P < 0.05). Variations in polypeptide composition affected metabolite abundance, notably impacting the urea cycle in Campylobacter and Clostridiaceae. DIC shifted communal energy metabolism in microbiota on casein sources.

Conclusion: Campylobacter's adaptability to the deaminase inhibitor indicates reliance on the microbial community and their metabolic products, showcasing its metabolic versatility.

Aims: Stipa purpurea is one of the dominant grass species in alpine grassland and plays a crucial role in safeguarding the ecosystem and restoring degraded grassland. To enhance the population dominance of Stipa purpurea and effectively prevent further grassland degradation. In this study, we screened high-efficiency PGPR from rhizosphere soil samples, with the aim of improving the growth activity of Stipa purpurea through spraying PGPR.

Methods and results: We selected functional medium for the isolation of PGPR from the rhizosphere soils of five distinct sampling sites in the alpine grasslands surrounding Qinghai Lake. Nitrogenase activity, phosphorus-solubilization, carbon-fixation, IAA-like compounds production, and ACC deaminase production were used to assess the growth-promoting capability of the PGPR. Additionally, the ecological adaptability of PGPR was examined. Finally, the growth promotion effect of high-efficiency PGPR on Stipa purpurea was determined using pot experiments. The results of this study showed that 136 strains were isolated and were categorized into 18 genera based on the 16S rRNA sequences. Among these, seven strains exhibited multiple characteristics of promoting growth, and meanwhile, strains GD-1-1, YD-2-4, GD-3-9, and HD-1-1 exhibited strong resistance to drought, cold, UV, and oxidation. The strains GD-1-1 and YD-2-4 had growth-promoting effects on the growth of Stipa purpurea, which significantly enhance the seed germination rate, facilitate the growth of the above-ground part of seedlings, and the formation of lateral roots. Additionally, the results of the principal component analysis indicated that the interaction effect of high-efficiency PGPRs with young roots was more beneficial than that with young sprout.

Conclusions: The results of this study provide outstanding strain resources and a theoretical foundation for the restoration of alpine degraded grassland. The findings further provide the basis for research and development of microbial fertilizer.

Aims: The impact of promoter selection on the overexpression of the XKS1 gene in Saccharomyces cerevisiae is investigated with a focus on optimizing xylose metabolism for second-generation ethanol production. The goal was to identify how different promoters affect the fermentation performance of laboratory and industrial yeast strains under various media conditions.

Methods and results: Four constitutive promoters-TEF1p, ADH1p, PGK1p, and TDH3p-were tested to overexpress XKS1 in two strains of S. cerevisiae, one laboratory strain (BY4742) and one industrial strain (PE-2B), both engineered with a heterologous xylose isomerase pathway. The strains were evaluated in defined (YNB) and complex (YPDX) media, as well as a synthetic sugarcane hydrolysate, over a 144-hour fermentation period. Promoter choice significantly influenced cell growth, xylose consumption and ethanol production. In the laboratory strain, TEF1p yielded the highest ethanol production in YPDX, while TDH3p promoted higher biomass formation. In the industrial strain, ADH1p, TEF1p, and PGK1p led to high ethanol yields in YPDX, with ADH1p showing superior performance in the synthetic hydrolysate. RT-qPCR reveals lower XKS1 expression levels render a better trait for BY4742, while the opposite is observed for PE-2B.

Conclusions: It is demonstrated that promoter selection is crucial for optimizing XKS1 expression and xylose metabolism in S. cerevisiae. Promoters must be carefully tailored to the yeast strain and fermentation conditions to maximize ethanol production, providing strategic insights for enhancing the industrial fermentation of lignocellulosic biomass.