International Microbiology最新文献

The study investigates the microbial composition of bat flies (Diptera: Nycteribiidae) collected from Myotis punicus in Algeria, focusing on the diversity and dynamics of their microbiota through network analysis. The analysis targets two genera, Nycteribia and Penicillidia, comparing oioxenous and stenoxenous species to understand host specificity's influence on microbial communities. Utilizing 16S rRNA sequencing, alpha and beta diversity metrics, and co-occurrence networks, the study assesses microbial diversity, community composition, and the impact of specific bacteria (endosymbionts, commensals, and pathogens) on network stability. Results reveal significant microbial community variations between genera and species, with N. latreillii exhibiting the most complex network. We showed that host specificity and feeding strategies significantly influence microbial diversity and interactions within bat flies. Robustness analysis through node removal simulations identifies the roles of key bacteria, such as Wolbachia, Arsenophonus, and Bartonella, in maintaining network stability. Findings highlight the complex interplay between these microorganisms and their hosts, offering insights into microbial ecology and vector-pathogen dynamics. The research underscores the importance of bat flies in shaping pathogen transmission networks, contributing valuable knowledge to wildlife ecology, disease control, and conservation strategies.

Malabar spinach (Basella alba L.) is a widely consumed leafy vegetable in Vietnamese daily meals. It has a short growth cycle but is susceptible to various diseases, of which the nematode Meloidogyne spp. is a significant factor causing yield reduction. This study focused on finding native plant growth-promoting rhizobacteria that can control root-knot nematodes and stimulate plant growth. The results isolated and selected Bacillus velezensis BHMT4.1, Staphylococcus carnosus CCMT2.1, and Pseudomonas fluorescens HMMT1.1, which showed promise in controlling Meloidogyne spp. in Malabar spinach and promoting plant growth. In the in vitro experiment, the B. velezensis BHMT4.1 strain caused the highest immobilization of J2 with 68.67%, followed closely by the P. fluorescens HMMT1.1 strain with 66.67%. The S. carnosus CCMT2.1 strain inhibited nematode egg hatching after 7 days, achieving a rate of 42.67%, while B. velezensis HMMT1.1 reached 44%. In addition, the B. velezensis BHMT4.1 strain demonstrated the best ability to produce siderophores on CAS agar after 48 h. The P. fluorescens HMMT1.1 strain exhibited the highest nitrogen fixation ability after 3 days of culture on the NFb medium. In greenhouse trials, Malabar spinach was inoculated with the S. carnosus CCMT2.1, reducing the number of galls to 16.29% in comparison to the control, which stood at 91.88%. Additionally, the nematode density in the soil decreased to 45.20 individuals compared to the control of 66.66 individuals (nematodes/50 g soil) after 28 days. This study showed that native bacterial strains found in vegetable soil have the ability to enhance plant development and protect Malabar spinach from being attacked by Meloidogyne spp. The results suggest that these bacterial strains could be further developed into potential biopesticides to help reduce root-knot nematode damage. Additional field studies are necessary to assess how well these bacteria adapt to the rhizosphere ecosystem of vegetable plants.

Soil salinization is a critical constraint on global rice production, posing a serious threat to food security and underscoring the urgent need for sustainable strategies to fortify plant stress resilience. In this context, this study demonstrates that SB24, a halotolerant PGPR isolated from saline rice fields, markedly improved the salinity tolerance of rice genotype Pusa 44 through coordinated physiological, biochemical, and molecular responses. This strain, identified by 16S rDNA sequencing, exhibited high salt tolerance (up to 16% NaCl) and possessed multiple plant growth-promoting traits. Under 125 mM NaCl stress, SB24 inoculation enhanced germination and growth, with significant increases in shoot and root biomass compared to uninoculated controls. SB24-treated plants showed elevated photosynthetic pigments (Chl a, Chl b, carotenoids), soluble sugars, and soluble proteins, alongside enhanced antioxidant enzyme activities (SOD, CAT, APX, PPO) significantly. These changes were accompanied by reductions in oxidative stress markers, including electrolyte leakage, H₂O₂ accumulation, lipid peroxidation, and lipoxygenase activity. SB24 also promoted osmolyte accumulation (proline, glycine betaine and maintained ion homeostasis by reducing Na⁺ uptake while increasing K⁺ and Ca^2⁺ retention. At the transcriptional level, SB24 upregulated the expression of key salt-responsive genes, including OsSOS1 (salt overly sensitive 1) 1.35-fold, OsNHX1 (vacuolar Na⁺/H⁺ antiporter 1) 1.5-fold, OsHKT1;5 (high-affinity K⁺ transporter 1;5) 1.23-fold, OsFeSOD (iron superoxide dismutase) 1.22-fold, and OsAPX (ascorbate peroxidase) 1.18-fold, validating the observed physiological, and biochemical responses to improved salt stress tolerance. Taken together, these findings establish SB24 as a potent bioinoculant with strong potential for mitigating salinity stress through integrated, multi-level mechanisms.

Gamma-aminobutyric acid (GABA) is a sedative drug capable of alleviating anxiety disorders, but its synthetic preparation is characterized by poor stability and insufficient bioavailability, along with its high cost. In this study, its precursor glutamic acid decarboxylase (GAD) from Lactobacillus casei IIB-09 was immobilized on biodegradable mesoporous silica nanoparticles (MSNPs) to improve the enzyme's catalytic efficiency and bioavailability, while providing a cost-effective synthetic approach. Under optimized culture conditions, i.e., 0.5% (w/v) monosodium glutamate (MSG) at pH 6.5 for 48 h with an inoculum size of 2% (v/v), the highest GAD activity (3.59 ± 0.01 IU/mL/min) and concentration of GABA (137 ± 0.01 mM) were achieved. GAD was physically immobilized onto biodegradable MSNPs and subsequently characterized using various analytical techniques. To confirm the crystalline nature of MSNP, X-ray diffraction (XRD) analysis was performed. Further, UV-Vis, SEM, and FTIR spectra verified the immobilization of GAD on MSNPs. After optimization of the immobilization process, the immobilized enzyme showed a twofold increase in activity (2.59 ± 0.03 IU/mL). A comparative analysis was done to examine the thermophilic characteristics and the activity of both free and immobilized enzymes under varying concentrations of methanol and α-ketoglutarate. The free and immobilized GAD exhibited maximum GABA production (112 ± 0.02-119 ± 0.03 mM) at 45 °C. This study highlights the true potential of immobilized GAD as a sustainable approach for its efficient biotransformation into GABA for applications in the pharmaceutical and functional food industries.

Anti-virulence strategies are gaining recognition as promising alternatives for bacterial infection control. They act by suppressing quorum sensing circuits, disrupting biofilm formation, and inhibiting toxin production. However, the emergence of resistant bacterial mutants highlights the need for anti-virulence agents that do not induce resistance. Pseudomonas aeruginosa produces autoinducers like N-acyl-homoserine lactone (AHL), which enhance cell-population and coordinate gene expression. Plant-derived compounds, particularly O-methylated phenolic flavonoids, have shown promise in overcoming antibiotic resistance. Herein, compounds such as formononetin (isoflavone) and 4'-methoxyflavonol (flavonol) possess pharmacological properties beneficial for human health and have been found to inhibit AHL-mediated virulence factors in P. aeruginosa. These flavonoids effectively reduced the production of virulence factors like exopolysaccharides, elastase, protease, pyocyanin, and rhamnolipids assessed by biochemical assays. Motility assays demonstrated a reduction in bacterial movement, and biofilm formation was quantified and visualized using Zeiss Confocal Laser Scanning Microscopy. Gene expression analysis by RT-qPCR revealed that the flavonoids suppressed las and rhl circuits associated with virulence factor synthesis. Among the selected two compounds, 4'-methoxyflavonol exhibited the strongest inhibitory effect against P. aeruginosa. Overall, this study underscores the dual role of dietary phenolic flavonoids in supporting biological functions and serving as natural anti-quorum sensing agents, offering promising strategies to mitigate bacterial virulence.

In this work, the isolation and identification of pigment-producing fungi from substrate samples collected in the Sonoran Desert, Mexico, are described. Three fungal isolates, named CR2, SM1, and GBS, were selected for their ability to produce colored pigments. The redox properties of these pigments were characterized using UV-Vis spectroscopy and cyclic voltammetry. The GBS pigment, produced by the fungus Forliomyces uniseptata, exhibited the best electrochemical behavior, with a reversible redox cycle, indicating its potential as a redox mediator (RM) for microbial fuel cells (MFCs). The effect of different light wavelengths on the growth kinetics of F. uniseptata and pigment production was evaluated. Blue light moderately accelerated pigment biosynthesis, while darkness promoted fungal growth. Finally, the GBS pigment was tested as a RM in a MFC inoculated with Bacillus subtilis. A maximum power density of 37 μW/cm². It is suggested that mass transfer could limit performance.

Salvia miltiorrhiza is a widely used medicinal plant, and post-harvest processing methods such as sweating may influence its metabolite composition and microbial interactions. However, the metabolic and microbial changes induced by sweating remain poorly understood. This study aimed to investigate how sweating affects the metabolite profile of S. miltiorrhiza and its associated bacterial communities, with a focus on identifying key metabolic shifts and microbial dynamics. Widely targeted metabolomics was employed to compare the composition and relative content of metabolites between control (non-sweated) and sweated S. miltiorrhiza plants. Additionally, high-throughput sequencing was used to analyze variations in bacterial communities at different sweating stages. A total of 435 differentially present metabolites were identified, categorized into 11 classes, with quinones, phenolic acids, and lipids being the most prominent. Sweating significantly increased microbial diversity and richness, and we established a correlation between the accumulation of quinones and phenolic acids and shifts in bacterial community structure. Notably, sweating enhanced the levels of key metabolites, which in turn promoted the relative abundance of potentially beneficial microorganisms. Furthermore, distinct bacterial populations at different sweating stages contributed to the unique quality traits of S. miltiorrhiza. The findings demonstrate that sweating not only alters the metabolite profile of S. miltiorrhiza but also shapes its associated bacterial communities, leading to improved accumulation of bioactive compounds.

Saprolegniasis is one of the most devastating fish diseases that cause fish mortality in aquaculture in winter season, leading to economic loss to the farmers. The mycotic infection in fish occurred during the winter season in inland open water bodies due to adverse environmental factors, poor culture practices, high stocking densities, rough handling, and physiological changes associated with immune suppression. In the present investigation, we studied the environmental factors for disease progress in Pangasianodon hypophthalmus and Labeo rohita, characterization of oomycetes, and screening of potential antifungal agents against fish pathogenic oomycetes. Mortality and infection patterns have a relationship with water temperature in the present investigation. We noted that co-habitat infection was found in L. rohita and caused mortality. The presence of certain abiotic factors and susceptible host species led to the outbreak of disease in cage culture. The morphological and molecular identification of the etiological agent was carried out, and the PCR amplicon sequence of the ITS gene fragment showed similarities with Saprolegnia aenigmatica. The optimum temperature required by S. aenigmatica was between 20 and 25 °C for hyphae growth. In vitro assessment revealed that fluconazole (FLZ), boric acid (BA), and potassium permanganate (KMnO4) were unable to control zoospore colonization at higher concentrations. Clotrimazole and hydrogen peroxide inhibited colonization in 10 ppm and 100 ppm, respectively. The present investigation identified and confirmed the causative agent of saprolegniasis outbreak with associated environmental factors and approached to develop antifungal therapeutics to combat infection in the inland open-water bodies.

Faba bean (Vicia faba L.) is a major legume crop with high nutritional and commercial value, but its output is severely limited by vascular wilt and root rot caused by Fusarium oxysporum. Biological control and other environmentally benign solutions provide long-term alternatives to toxic fungicides. Under controlled conditions, the cyanobacterium Trichormus variabilis and the endophytic bacterium Priestia endophytica were tested for their biocontrol potential against Fusarium oxysporum. Plant defense responses were evaluated using total phenols, proline, and peroxidase activity. Infection with Fusarium oxysporum significantly raised stress indicators, such as phenols (71.97 mg g⁻¹), proline (5.54 mg g⁻¹), and peroxidase (6.35 U g⁻¹). Single treatments of either bioagent reduced stress, decreased phenolic buildup, and restored enzymatic equilibrium. The combination treatment offered the strongest protection, decreasing stress indicators to 58.9 mg/g phenols, 3.42 mg/g proline, and 4.54 U/g peroxidase. Bioagents increased soil microbial activity, including dehydrogenase (4.69 mg TPF g⁻¹ soil in Trichormus variabilis vs. 2.5 in Fusarium oxysporum), chitinase (4.07 U mL⁻¹ in the combined treatment vs. 1.40 in control), and protease (4.50 U g⁻¹ soil in the combined treatment vs. 1.70 in control). The enzymatic stimulation increased plant health and resistance. Trichormus variabilis and Priestia endophytica had a synergistic impact against Fusarium oxysporum, making combination application the most promising technique for long-term management of faba bean root rot.