Journal of Applied Microbiology最新文献

Aims: Tuberculosis (TB) remains a major global health threat, underscoring the urgent need for novel therapeutics. 5-Iodotubercidin (5-ITu), a purine-based protein kinase inhibitor, has not been previously evaluated for anti-tuberculosis (anti-TB) applications.

Methods and results: This study presents the first comprehensive characterization of 5-ITu as a lead compound for TB treatment, focusing on its antimicrobial activity, pharmacokinetic (PK) properties and safety profile. 5-ITu exhibited notable antimicrobial activity against Mycobacterium tuberculosis (MTB) standard strain H37Rv and 25 multidrug-resistant (MDR) clinical isolates, with MIC values ranging from 0.23 to 0.9 μg ml-1, while showing MIC values >32 μg ml-1 against eight other bacterial strains. Checkerboard assays revealed synergy with multiple anti-TB drugs against clinical MDR isolates. The permeabilizing effect of 5-ITu on the bacterial inner membrane, along with the associated dissipation of membrane potential and reduction of intracellular ATP, was confirmed by membrane integrity and function assays. PK study in mice following oral administration of 10 mg kg-1 showed rapid absorption, high plasma exposure, and an atypical plateau during the elimination phase. Cytotoxicity assays and acute toxicity studies in mice revealed moderate toxicity of 5-ITu toward mammalian cells and rodents.

Conclusions: Despite its moderate toxicity, the promising anti-TB activity and favorable PK profile of 5-ITu support its potential as a lead compound for structural optimization in anti-TB drug development.

Aims: Recent developments have revealed gut microbiota is involved in the development of high-altitude pulmonary hypertension (HAPH). As ultrasound-targeted microbubble destruction (UTMD) can augment tissue perfusion, it might influence the HAPH. Therefore, this study explored the effects of UTMD on gut microbiota tentatively, emphasizing the impact of UTMD on HAPH.

Methods and results: Fifteen mice were divided into normoxia (Nor), hypoxia (Hyp), and UTMD-treated (Hyp + UTMD) groups. The Nor group was raised under normobaric normoxia, whereas Hyp was placed in a hypoxic chamber simulating low oxygen levels at high altitude. The Hyp + UTMD group was placed in the same chamber with UTMD exposed every three days for 8 w. Fecal samples of mice in each group were collected at 4 and 8 w, and all mice were subjected to a hemodynamic assay on 57th day for right ventricle systolic pressure (RVSP) monitoring, which could have direct and lasting physiological effects on the nervous, cardiovascular, respiratory, and digestive systems. 16S rRNA sequencing analysis revealed gut microbiota modification in both Hyp and Hyp + UTMD. The Firmicutes/Bacteroidetes ratio in Hyp1 (75.97%) was significantly higher than that in Nor (43.70%) and Hyp + UTMD1 (24.55%). Compared with microbiota in Hyp1, 3 bacterial phyla were increased, including p_Bacteroidetes, p_Epsilonbacteraeota, and p_Verrucomicrobia, whereas p_Firmicutes was decreased in Hyp + UTMD1. And g_Alloprevotella was significantly upregulated in Hyp + UTMD1 and Hyp + UTMD2, which was downregulated in the Hyp. Hyp + UTMD RVSP (29.7 mmHg) was significantly suppressed when compared to Hyp (36.5 mmHg), and g_Alloprevotella exhibited a significant negative correlation with RVSP.

Conclusion: UTMD-mediated modification of the gut microbiota suppresses the development of hypoxic-induced HAPH, highlighting the potential of UTMD treatment that modulate gut microbiota to prevent hypoxic pulmonary hypertension.

Aims: Meat can harbor microbial pathogens, posing hazards for public health. In the European Union, microbiological food safety standards for meat are mainly at the processing level, with limited data and criteria on microbial contamination and pathogen presence at retail. This study addresses this gap by quantifying and comparing microbial loads on various meat types.

Methods and results: A total of 286 samples, including minced beef and fillets, minced pork and fillets, minced chicken, and chicken carcasses and fillets, were obtained from supermarkets and butcheries in Flanders, Belgium. Microbiological analysis was performed to determine total aerobic bacteria (TAB), presumptive Pseudomonas and Escherichia coli counts, and to detect Campylobacter spp. and Salmonella spp. Results showed significant variations across different meat types and retail sources, with chicken carcasses from butcheries harboring the highest TAB counts (7.38 ± 1.09 log10 CFU g-1, Median ± IQR) and presumptive Pseudomonas counts (7.55 ± 1.11 log10 CFU g-1). Escherichia coli was predominantly present on chicken products, while most of the beef and pork samples had counts below 10 CFU g-1. Salmonella was detected in 4.9% of chicken samples, exclusively from supermarkets, while Campylobacter was present on 14.8% of the butchery samples, and 20.8% of the supermarket chicken samples.

Conclusions: These findings reveal high microbial contamination levels on meat and the prevalence of high-risk pathogens. Therefore, supporting the need for microbial standards and interventions in the meat sector, especially for chicken products and meats sold in butcheries, to better protect public health and enhance consumer confidence.

Aims: Understanding the microbiota of powdered infant formula (PIF) products may provide important insights that are not seen with currently mandated microbiological testing. This work aimed to identify the load and taxonomy of microorganisms which persist through recommended preparation methods and increasingly popular at-home preparation machines (APHM).

Methods and results: PIFs were purchased from commercial suppliers to cover the majority of available brands and products in the UK. PIF was prepared using either advised sterile 70°C water, sterile room temperature water, or a popular AHPM. Preparations were plated onto Tryptic soy agar and Sabourhaud dextrose agar. Total aerobic counts were taken and isolates identified via MALDI-ToF mass spectrometry. Overall microbial populations were significantly different due to preparation method and bacterial populations were significantly different between PIFs (P < 0.05). Four PIFs showed within product significant differences caused by the preparation method. No significant difference occurred in microbe levels amongst brands and product types. AHPM prepared milks had unique microbial recoveries. Potential pathogens were isolated including Bacillus cereus resistant to imipenem and meropenem. B. cereus showed temperature resistance above the WHO recommended temperature of 70°C.

Conclusions: Current preparation guidance may not remove all microbial contaminants of PIFs, including the opportunistic pathogens identified in this work. These appear to be primarily environmental contaminants, and which may present a currently underappreciated concern with regards to infant microbiome development.

Aims: Potato late blight, caused by the Phytophthora infestans, is one of the most devastating diseases impacting potato yield. This study investigates the potential role and mechanism of Paenibacillus polymyxa YF and Bacillus amyloliquefaciens HT as biocontrol agents against potato late blight.

Methods and results: In vitro antagonism assays showed both strains effectively inhibited mycelial growth of P. infestans. In sporangia germination tests, either strain reduced germination by over 80% at 50% concentration. Enzymatic and biochemical assays revealed they secreted multiple extracellular enzymes and produced siderophores and IAA-like compounds. Strain YF exhibited significantly stronger inhibition and robust potato root/stem colonization in preliminary screens, so it was selected for subsequent in planta studies. In excised tissue and potted plant experiments, strain YF-treated groups had significantly lower disease severity indices and higher biomass than controls. Biochemical assays also showed YF inoculation significantly increased the activity of four resistance enzymes compared to controls.

Conclusions: Overall, this study's findings provide a theoretical foundation for leveraging strain YF and strain HT as potential biocontrol agents, with strain YF showing particularly high promise due to its efficacy in disease suppression and bolstering plant growth and resistance mechanisms.

Aim: This study aims to delineate the characteristic profiles of gut microbiota and fecal metabolites in individuals diagnosed with intervertebral disc degeneration (IDD), potentially elucidating the gut-disc axis as a novel perspective for understanding IDD pathophysiology.

Methods and results: Fecal samples were collected from 15 patients diagnosed with IDD, classified according to the Pfirrmann grading system, with a distribution of three individuals per grade. Additionally, samples were obtained from five healthy controls for comparative analysis. 16S rDNA sequencing was employed to analyze gut microbiota composition, while liquid chromatography-mass spectrometry was used for untargeted metabolite profiling. Distinct gut microbiota signatures were observed in IDD patients compared to controls, characterized by a dysbiotic state with increased biodiversity. More importantly, patients with IDD exhibit a higher abundance of Proteobacteria and Fusobacteriota, along with reduced abundances of Campilobacterota and Synergistota at the phylum level, as determined by Linear Discriminant Analysis Effect Size (LEfSe). Fecal metabolite analysis revealed an altered metabolic profile in IDD patients, including aggrandized levels of lipids and lipid-like molecules, which are associated with oxidative stress and tissue degradation. KEGG pathways identified five significant ones, including Nucleotide metabolism, Taurine and hypotaurine metabolism, Arginine and proline metabolism, Carbohydrate digestion and absorption, and FoxO signaling pathway. Together with receiver operating characteristic analysis, our data indicate that the upregulation of Permethrin and the reduction of 3ccPA, Thymine, His-ser, Hypoxanthine, N6-Acetyl-L-lysine, Safranin, and Peimine are highly associated with IDD.

Conclusion: Our findings suggest a strong association between gut microbiota dysbiosis and fecal metabolite alterations in the pathogenesis of IDD.

Aims: Bacterial spot disease caused by Xanthomonas spp. is a major threat to tomato production that leads to significant yield losses. As these pathogens invade through stomata and wounds, understanding the phyllosphere microbiome dynamics during infection is critical for identifying potential biocontrol agents. In this study, we profiled the tomato phyllosphere microbiome shift during Xanthomonas infection, assessed the antagonistic activity of a phyllosphere bacterium, and characterized its genetic features through whole genome analysis.

Methods and results: Phyllosphere microbiome analysis was performed on control and Xanthomonas-infected tomato plants using the leaf swabbing method and 16S rRNA gene amplicon sequencing with various primer sets. A significant increase in the abundance of Acetobacteraceae in infected plants prompted the targeted cultivation of the taxon, which subsequently led to the isolation of strain T12B. It exhibited strong in vitro and in vivo antagonistic activity against Xanthomonas, primarily through organic acid production. Whole genome analysis confirmed T12B as Gluconobacter japonicus subsp. japonicus. The genome of T12B encodes 2792 coding DNA sequences, including complete pathways for acetic, gluconic, and ketogluconic acid biosynthesis, as well as other putative genes that may contribute to its antagonistic activity against Xanthomonas.

Conclusions: Tomato phyllosphere microbiome profiling facilitated the targeted isolation of G. japonicus T12B that demonstrated potential for disease suppression and biocontrol applications in tomato.

Aims: Lanzhou lily (Lilium davidli var. unicolor) possesses both nutritional and medicinal value, however, its bulbs are highly susceptible to postharvest physical damage. Pathogenic bacteria readily infiltrate through these wounds, resulting in extensive decay and consequent economic losses. This study demonstrates that optimized volatile organic compound (VOC) combinations can significantly reduce effective antimicrobial concentrations and broaden the antimicrobial spectrum through synergistic effects, while exhibiting excellent preservation potential.

Methods and results: From decayed lily bulbs, this study isolated and identified two bacterial strains, Bacillus cabrialesii SH-3 and Bacillus amyloliquefaciens SH-5, both exhibiting opportunistic pathogenicity. Fifteen binary VOC combinations were evaluated using fractional inhibitory concentration index (FICI), identifying QM (1/8 MIC 2-methylbutyric acid + 1/8 MIC 3- methylpentanoic acid, FICI = 0.25) and QH (1/2 3-methylpentanoic acid + 1/8 3-hepten-2-one, FICI = 0.625) as optimal formulations. Mechanistic studies revealed these combinations disrupt bacterial membrane integrity, induce protein/nucleic acid leakage, and trigger oxidative stress and metabolic dysfunction.

Conclusions: Against SH-3, only QM showed synergistic effects, reducing required concentrations by 87.5% compared to individual minimum inhibitory concentration (MIC). For SH-5, all combinations demonstrated additive effects, with QH achieving potent inhibition at 50% and 87.5% reduced concentrations for respective components. Applied at MIC levels, both formulations significantly suppressed postharvest decay while maintaining bulb quality.

Aims: Plant diseases caused by pathogenic microorganisms are among the major challenges in global agricultural production, necessitating the search for bioactive natural compounds with effective antimicrobial activity. This study investigates the potential of Lentinus tigrinus culture filtrate extract for the discovery of compounds active against agriculturally important pathogens.

Methods and results: The culture filtrate of the mushroom L. tigrinus was subjected to bioassay-guided fractionation, leading to the isolation of five compounds. These were identified by mass spectrometry, nuclear magnetic resonance, and optical rotation analyses as (R)-mellein (1) and its derivatives: (R)-5-methoxycarbonylmellein (2), (3S,4S)-4-hydroxymellein (3), (3R,4S)-4-hydroxymellein (4), and (S)-8-O-methylmellein (5). All compounds were tested in vitro against four plant pathogenic fungi and four plant pathogenic bacteria. Compound 2 exhibited the strongest antifungal activity, particularly against Pyricularia oryzae, inhibiting conidial germination (IC₅₀ 30.2 μM) and germ tube elongation (IC₅₀ 20.7 μM). In vivo, compound 5 suppressed rice blast lesion symptoms caused by P. oryzae. Compound 1 showed the most potent antibacterial activity. Based on IC₅₀ values, all compounds were more effective against fungi than bacteria.

Conclusions: The inhibitory activities of the five isolated compounds against plant pathogenic fungi and bacteria suggest their potential as lead compounds for agrochemicals for managing plant diseases.

Aims: The present study aimed to explore microbial production of neurotransmitters related to cognitive function in the faecal microbiota of healthy older adults, and assess whether a multi-strain probiotic formula may influence production of these neuroactive metabolites, short-chain fatty acids, and the bacterial community.

Method and results: The current study employed a three-stage continuous culture system with faecal microbiota from three healthy older adult donors. Neuroactive compounds were quantified using liquid chromatography mass spectroscopy, SCFAs using gas chromatography, and the bacterial community was assessed using fluorescence in situ hybridization with flow cytometry and 16S rRNA sequencing. Addition of the probiotic supplement (Bifidobacterium lactis W51, Bifidobacterium lactis W52, Lactobacillus acidophilus W37, Lactobacillus salivarius W24, Lactobacillus casei W56, Bifidobacterium bifidum W23, Lactobacillus brevis W63, Lactococcus lactis W19, Lactococcus lactis W58) significantly increased the relative abundance of Lactococcus lactis in the transverse region, alongside a trend for increased Roseburia across the three colon regions modelled, valerate in the distal region, and GABA in the proximal region.

Conclusions: While administration of the probiotic only had a small effect of trending increases in the synthesis of GABA and valerate, this highlights important mechanisms by which probiotics could be involved in the gut-brain axis. The model also enabled the observation of limited microbial production of other neurotransmitters. Further exploration in human studies is therefore warranted. Probiotics were confirmed to lead to microbial changes, both directly (Lactococcus) and indirectly (Roseburia). This research helps to support mechanistic understanding of probiotics and the gut-brain axis.