Microbiological research最新文献

Hexanoic acid (Hx) is a naturally occurring fatty acid with antimicrobial properties and potential to induce plant defense responses. This study evaluated the in vitro effect of Hx on Xanthomonas vesicatoria and Xanthomonas euvesicatoria, focusing on bacterial growth and biofilm formation, key factors for pathogen survival and virulence. The obtained results indicate that Hx did not exert a direct lethal effect at low concentrations on bacterial cells, but higher doses (≥ 12 mM) displayed a bactericidal effect against both species, with X. euvesicatoria showing higher sensitivity than X. vesicatoria. Scanning electron microscopy (SEM) revealed cell wall damage and absence of biofilm at ≥ 10 mM Hx, consistent with the quorum sensing (QS) inhibition observed at this concentration. Moreover, exposure to 5 mM Hx triggered a significant increase in reactive oxygen species (ROS), indicating the inability of both bacteria to overcome the toxic environment generated by this compound. In addition, gene expression analysis demonstrated that Hx significantly impaired early biofilm establishment by downregulating motility- and virulence-related genes, particularly evident in X. euvesicatoria from lower concentrations. Although responses differed between the two species in survival strategies and sensitivities to Hx, both converged in a compromised biofilm formation and stress response capacity. Overall, this study provides mechanistic insights into Xanthomonas sensitivity to Hx and highlights biofilm disruption as a central mechanism underlying its antimicrobial activity under in vitro conditions.

Helicobacter pylori (H. pylori) infection is a major risk factor for gastric cancer (GC), but the molecular mechanisms driving H. pylori-induced gastric carcinogenesis remain incompletely understood. This study investigates the role of the AEG-1 3'-untranslated region (3'UTR) as a competitive endogenous RNA (ceRNA) in this process. A ceRNA network was constructed via whole-transcriptome sequencing of H. pylori-associated GC. Gain- and loss-of-function experiments were performed to assess the impact of the AEG-1 3'UTR on epithelial-mesenchymal transition (EMT) in infected GC cells. The regulatory mechanism was explored using bioinformatics, dual-luciferase reporter assays, and rescue experiments. In vivo effects were evaluated using AEG-1 knockout mouse models of H. pylori infection and nude mouse xenograft models. Results showed that AEG-1 and JAK2 were upregulated and miR-375-3p downregulated in H. pylori-infected GC cells and tissues. The AEG-1 3'UTR promoted proliferation, migration, invasion, and EMT by sponging miR-375-3p, thereby derepressing JAK2 and activating JAK2/STAT3 signaling. These oncogenic effects were reversed by JAK2 silencing or miR-375-3p overexpression. In AEG-1 knockout mice, H. pylori colonization and gastric inflammation were markedly reduced, accompanied by decreased expression of EMT and proliferation markers. Xenograft models further confirmed that the AEG-1/miR-375-3p/JAK2 axis drives GC growth and lung metastasis. These findings identify AEG-1 3'UTR as a ceRNA that regulates H. pylori-mediated EMT and carcinogenesis via the miR-375-3p/JAK2 axis, highlighting its potential as a therapeutic target.

The application of salt-tolerant plant growth-promoting rhizobacteria (PGPR) represents a promising strategy to alleviate salt stress in crops. However, the mechanisms by which volatile organic compounds (VOCs) from actinomycetes mitigate salinity stress remain unclear. In this study, exposure to VOCs from the halotolerant actinomycete Glutamicibacter halophytocola KLBMP 5180 significantly promotes the growth of tomato seedlings under salt stress, as evidenced by increased fresh weight, lateral root number, and chlorophyll content. Physiological analyses show that VOCs exposure reduces oxidative damage and enhances antioxidant enzyme activity. Furthermore, elevated levels of total phenolics and flavonoids are detected, along with decreased sodium ion accumulation and an improved Na⁺/K⁺ ratio. Transcriptome analysis reveales that VOCs treatment upregulates genes associated with pathways involved in phenylpropanoid biosynthesis, glutathione metabolism, MAPK signaling, plant hormone signal transduction, and plant-pathogen interactions under saline conditions. VOCs also increase levels of endogenous auxin, jasmonic acid (JA), and 1-aminocyclopropane-1-carboxylic acid (ACC), while activating genes related to their respective signaling pathways. The salt tolerance enhancement mediated by VOCs is compromised by ethylene and JA inhibitors, suggesting that KLBMP 5180-derived VOCs improve tomato salt tolerance by stimulating ethylene synthesis and signal transduction. Additional VOCs profiling identifies several key bioactive compounds, including 3-methyl-1-butanol, phenylethyl alcohol, 2-aminopropanediamide, and 2-undecanone. These findings demonstrate that VOCs from G. halophytocola KLBMP 5180 enhance tomato growth under salt stress and advance our understanding of the role of actinomycetes in pronoting plant growth and mitigating salinity stress.

Improper seed storage conditions, such as elevated temperature and moisture, accelerate ageing and compromise seed quality. However, the impacts of ageing on the seed microbiome and the resulting consequences for germination performance remain poorly understood. Here, we characterised how ageing soybean (Glycine max) seeds at 45 °C and 75% RH affects seed fungal communities, metabolism relevant to microbial growth, and sensitivity of germination to fungal challenge. Additionally, we assessed a role for endophytic bacteria in controlling pathogenic fungi. Amplicon sequencing revealed that ageing decreased fungal richness and reshaped community structure and composition of dominant taxa in seeds. Fusarium and Rhizopus isolates inhibited germination of non-aged seeds, whereas Sarocladium, Plectosphaerella, and Cladosporium impaired germination of aged seeds only. During imbibition, ageing increased seed metabolite leakage, including pinitol, glucose, and fructose, which promoted fungal growth in vitro. Among 39 endophytic bacteria previously isolated from soybean seeds, Bacillus toyonensis C55 and B. pumilus AM26 antagonised fungal growth, consistent with genomic regions associated with antifungal activity. Ageing oxidised the seed cellular redox state, and fungi tolerated oxidative growth conditions better than bacteria. In two cultivars, seed inoculation with B. toyonensis C55 increased germination, supporting a role in regulating fungal infections, whereas B. pumilus AM26 impaired germination. Notably, neither Bacillus strain affected germination of high-vigour non-aged seeds. Fluorescence in situ hybridisation microscopy revealed that both strains recolonised the seed endosphere following ageing. We conclude that oxidation during seed ageing contributes to increased sensitivity to fungal pathogens, which can be modulated by certain bacteria.