Journal of Applied Microbiology最新文献

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: This study aimed to elucidate the dynamics of soil microbial communities during ecological restoration on degraded mountain slopes, specifically comparing the impacts of two common strategies: aggregate spray-seeding and planted forest establishment, against undisturbed natural slopes, and assessing key drivers of microbial recovery.

Methods and results: Soil microbial community composition (bacteria and fungi), diversity, and co-occurrence network structure were analyzed 7 years after restoration initiation. Both restoration approaches facilitated microbial community recovery, with restored slope compositions converging towards natural slope baselines. Fungal communities exhibited greater OTU diversity than bacteria, attributed to engineered substrates and rapid vegetation stabilization from spray-seeding. Crucially, restoration successfully increased microbial network complexity. Spray-seeding specifically achieved network stability comparable to natural ecosystems. Significant environmental relationships were identified: soil water content (SWC) showed negative correlations with fungal richness and composition, while belowground biomass (BGB) positively correlated with bacterial composition.

Conclusions: Restoration effectively promotes soil microbial community recovery towards natural ecosystem states, albeit with distinct dynamics for bacteria and fungi. Fungal communities are particularly responsive to restoration techniques like spray seeding. Soil properties (SWC) and plant development (BGB) are pivotal drivers shaping microbial assemblage during restoration.

Aims: Chelating agents are metal-sequestering compounds with antibacterial properties suitable for commercial and therapeutic applications. This study investigated the involvement of metal restriction and membrane disruption in the antibacterial mode of action of three chelators.

Methods and results: The antibacterial, metal sequestration, and membrane disruptive effects of ethylenediaminetetraacetic acid, diethylenetriamine pentamethylene phosphonic acid, and fusaric acid were examined across five bacterial species. ICP-MS was used to determine the impact on bacterial metal composition, while RT-qPCR of selected genes allowed evaluation of changes in cellular responses to intracellular metal depletion. Mutants defective in metal import and export machinery were also examined to validate processes critical for resistance. Chelator-mediated disruption of membranes was investigated using 1-N-phenylnapthylamine and propidium iodide. Finally, the capacity of two of the chelators to potentiate the activity of ampicillin, chloramphenicol, tetracycline, and three aminoglycosides was assessed in chequerboards. The results show that these chelators restrict access to iron, zinc, manganese, and calcium to varying degrees in these bacterial species, reflecting important differences in envelope architectures and metal handling capabilities.

Conclusions: This study shows that all three chelators behave differently in restricting metal access and possess antibacterial properties that often act synergistically in combination, notably with other antimicrobials.

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.

Aims: Non-alcoholic fatty liver disease (NAFLD) is a prevalent chronic liver condition, affecting 25% of adults globally, with risks of progression to severe complications such as cirrhosis and hepatocellular carcinoma. Emerging evidence highlights gut microbiota dysbiosis in NAFLD pathogenesis, suggesting probiotics as promising interventions. This study aimed to evaluate the potential of Lacticaseibacillus paracasei HP-B1337 as a probiotic for NAFLD management through phenotypic, genotypic analyses, and in-vivo mouse model.

Methods and results: The strain L. paracasei HP-B1337 was identified using colony morphology, physiological and biochemical characterization, carbon utilization tests, and whole-genome sequencing. Its safety profile was assessed via minimum inhibitory concentration testing, genotype-based antibiotic resistance analysis, biogenic amine production assays, and genetic screening for virulence and pathogenic factors. Probiotic properties, including acid and bile salt tolerance, antimicrobial activity against pathogens, adhesion capacity, and beneficial gene identification, were investigated. Additionally, the anti-NAFLD potential of HP-B1337 was validated in a high-fat diet (HFD)-induced mouse model. The results demonstrated that HP-B1337 exhibits robust probiotic characteristics, a favorable safety profile, and significant efficacy in alleviating HFD-induced fatty liver disease in mice.

Conclusions: Findings of this study provide strong evidence supporting the candidacy of HP-B1337 as a probiotic for NAFLD management.

Aims: The control of the common cockchafer Melolontha melolontha using the entomopathogenic fungus (EPF) Beauveria brongniartii is one of the most successful biological control systems. This study aimed to identify factors influencing the outcome of laboratory bioassays, which are crucial early steps in the development of biocontrol products, by using this system as a role model.

Methods and results: We combined spray and injection applications of conidio- and blastospores of the host-specific pathogen B. brongniartii BIPESCO2 (Bip2) and the generalist EPF Metarhizium brunneum Ma 43 and applied the treatments to cockchafer adults and larvae. Furthermore, the mycotoxin oosporein was tested alone or with Bip2 blastospores, as well as Bip2 conidiospores, in immersion, spray, and injection treatments of larvae. The most efficient spore suspension was applied to different larval body parts and to their food. Bip2 and Ma 43 infected adults frequently, but larvae resisted topical spray applications. Injection treatments revealed that adult cuticles offered limited protection, whereas the larval cuticle acted as an effective barrier. Larval thorax and legs, with articulations and intersegmental membranes, were more susceptible than the abdomen. Oosporein synergized with blastospores in larval immersion treatments, but alone had no effect. We propose that oosporein's antibiotic activity disrupts the larval cuticle microbiome, facilitating infection.

Conclusion: Contrary to the assumption that laboratory bioassays overestimate EPF performance under field conditions, we found the opposite. We therefore argue that more elaborate studies are required for realistic evaluation of candidate biocontrol agents, considering host-pathogen traits and test conditions.