Frontiers in Microbiology最新文献

Introduction: Saline-alkali soils severely limit agricultural Q7 productivity and ecological sustainability, particularly in coastal regions.This study evaluated the interactive effects of maize straw incorporation and improved irrigation on soil physicochemical properties, enzyme activities, and microbial community structure in saline-alkali soil through a field experiment.

Methods: Soil organic matter, nitrogen forms, available nutrients, salinity, and electrical conductivity were determined, together with key enzyme activities (sucrase and polyphenol oxidase) and bacterial and fungal community composition. Microbial functional potential was further explored using functional gene prediction.

Results: Compared with the control, the combined treatment significantly increased soil organic matter by 86.73% and available nutrients by 59.28%, while markedly reducing soil salinity and electrical conductivity by 53.56 and 47.12%, respectively. Soil enzyme activities responded differentially, with sucrase activity increasing by 109.23% and polyphenol oxidase activity decreasing by 29.35% compared with the control. Microbial community composition shifted substantially, characterized by a decline in halotolerant taxa (e.g., Flavobacteriaceae) and enrichment of carbon-cycling-associated bacteria (e.g., Cyanobiaceae), along with increased relative abundance of functional fungi such as Psathyrellaceae. Functional gene prediction revealed significant upregulation of carbohydrate metabolism pathways, including glycolysis and the tricarboxylic acid (TCA) cycle, indicating enhanced microbial metabolic capacity.

Discussion: Overall, maize straw incorporation combined with improved irrigation effectively enhanced soil quality, reshaped microbial community structure, and strengthened microbial functional potential. These findings provide practical evidence that integrated straw-irrigation management can serve as a feasible and sustainable strategy for the remediation and productive utilization of saline-alkali soils.

Introduction: Irritable bowel syndrome (IBS) is a typical disorder of gut-brain interaction (DGBI). The microbiota-gut-brain (MGB) axis is pivotal in preventing and treating IBS. Wuji Pill is a traditional Chinese medicine commonly used to treat IBS. This study aimed to investigate the mechanism by which Wuji Pill improves IBS via the MGB axis.

Methods: The visceral sensitivity and colonic motor function were evaluated using the abdominal wall withdrawal reflex test and the colonic motility curve. Depression-like behavior were evaluated using sucrose preference test, open field test, novelty-suppressed feeding test, and forced swimming tests. The intestinal mucus secretion and the activation status of microglia was detected using AB-PAS staining and immunofluorescence staining, respectively. The species composition and abundance of gut microbiota were detected through 16S rRNA sequencing and RT-qPCR. Targeted metabonomics and RT-qPCR were used for metabolites and metabolic enzymes analysis.

Results: In this study, Wuji Pill improved the symptoms of IBS rats and increased the relative abundance of Akkermansia muciniphila in feces. Additionally, antibiotics affected the repair of intestinal mucus secretion and significantly reduced the level of short-chain fatty acids. Subsequently, fecal microbiota transplantation and A. muciniphila transplantation can improve the symptoms of IBS rat by increasing intestinal mucus secretion, elevating the levels of acetic acid and butyric acid in feces. Additionally, the microglia in the cortex were suppressed, and the tryptophan-kynurenine pathway in the hippocampus was inhibited, leading to the conversion of tryptophan into 5-HT.

Discussion: This study highlights the Wuji Pill may alleviate IBS symptoms by modulating A. muciniphila and regulating the tryptophan metabolism pathway through MGB axis.

Background and objective: Brucellosis is a common zoonotic disease worldwide. Because its symptoms are non-specific and laboratory findings vary, diagnosis remains challenging. Blood culture is still the gold standard for confirmation, but its yield is often limited. This study aimed to estimate blood-culture positivity among hospitalized male patients with newly diagnosed brucellosis and to identify clinical and laboratory factors independently associated with culture positivity within confirmed cases.

Methods: We conducted a hospital-based retrospective study of 1,188 hospitalized men with newly diagnosed brucellosis admitted to a tertiary infectious-disease hospital in China between 2021 and 2023. Demographics, clinical manifestations, laboratory parameters, and blood-culture results were collected. Multivariate logistic regression was used to identify independent predictors of a positive blood culture.

Results: The overall blood-culture positivity rate was 30.9%. Univariate analysis indicated that disease stage, fatigue, fever, anorexia, splenomegaly, arthritis, paraspinal abscess, joint effusion, platelet count (PLT), alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), albumin (ALB), total bilirubin, lactate dehydrogenase (LDH), serum agglutination test (SAT), procalcitonin (PCT), and erythrocyte sedimentation rate (ESR) were associated with culture positivity. After multivariate adjustment, LDH, SAT, PCT, and ESR emerged as independent predictors of a positive blood culture, with PCT showing the strongest predictive value. Higher levels of LDH, SAT, PCT and ESR were independently associated with higher positive rates of blood cultures.

Conclusion: In this hospital-based retrospective cohort of confirmed brucellosis, LDH, SAT titer, PCT, and ESR were independently associated with blood-culture positivity. These routinely available parameters may help risk-stratify bacteremic likelihood and support culture-related decision-making (e.g., prioritizing sampling and considering repeat cultures when clinically warranted) among SAT-positive (or otherwise confirmed) patients, but they should not be interpreted as standalone markers for diagnosing Brucella bacteremia without microbiological confirmation.

Purpose: To assess the antioxidant-rich fraction of Murraya koenigii for its anti-infective properties against Gram-negative pathogenic bacteria by in vitro and in silico approaches.

Results: The most antioxidant active fraction, i.e., M. koenigii chloroform fraction (MKCF), significantly reduced violacein production (70.73%) in Chromobacterium violaceum 12,472. Significant reduction in prodigiosin production, protease activity, and swarming motility of Serratia marcescens, and other tested virulence factors of Pseudomonas aeruginosa PAO1 was recorded. More than 60% reduction in biofilm formation was recorded against test pathogens, indicating broad-spectrum anti-infective activity. SEM and CLSM imaging revealed alterations in the structure of the biofilm. Major key compounds such as Gibberellic acid, methyl ester, 7,8-Epoxylanostan-11-ol, 3-acetoxy were detected by GC/MS, and numerous compounds in MKCF were identified using LC-qTOF/MS analysis. In silico analysis revealed morellin and murrayazolinol with good binding affinity with CviR and EsaI, with binding energies of -9.07 and -9.17 kcal mol^-1, respectively.

Conclusion: The most active antioxidant fraction, i.e., MKCF, could be exploited as an anti-infective agent against Gram-negative bacterial pathogens, attenuating virulence and pathogenicity. Further, in vivo efficacy of the active fraction/phytocompounds needs to be evaluated to explore the therapeutic potential of MKCF.

Introduction: Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a serious threat to public health. We characterized a rarely reported ST627-KL8 CRKP lineage associated with intensive care unit (ICU) transmission.

Methods: Three isolates (ZJG29565, ZJG30140, and ZJG30146) were obtained from three patients in the ICU and subjected to antimicrobial susceptibility testing. Whole-genome sequencing (WGS) was performed to determine genomic characteristics, phylogenetic relationships, and plasmid content, followed by assessments of mucoviscosity, capsule quantification, serum resistance, and bacterial virulence using a Galleria mellonella (G. mellonella) infection model. Additionally, bacterial capsule morphology was observed via transmission electron microscopy (TEM).

Results: SNP analysis (≤ 5 SNPs) confirmed clonal transmission within the ICU. Phylogenetic analysis placed ST627-KL8 as a distinct lineage closely related to ST14. All isolates carried an IncFII_K34 plasmid encoding bla _KPC-2, consistent with their carbapenem-resistant phenotype. Phenotypic assays-including TEM, mucoviscosity testing, serum resistance, and uronic acid quantification-demonstrated a thinner capsule and reduced mucoviscosity compared with the KL2 reference strain. In the Galleria mellonella model, ST627-KL8 exhibited intermediate virulence (66.7%-76.7% survival), between the hypervirulent K. pneumoniae ATCC 43816 strain (30.0%) and the low-virulence K. pneumoniae ATCC 700603 strain (96.7%).

Discussion: This study identified a novel ST627-KL8 CRKP clone with intermediate virulence, consistent with its reduced capsule phenotype and lack of classical hypervirulence genes. These features, together with the subtle clinical presentations, may contribute to reduced clinical vigilance and delayed optimization of antimicrobial therapy. Importantly, ST627-KL8 CRKP carried the IncFII_K34 bla _KPC-2 plasmid, which has been reported to exhibit high conjugation frequency, posing a significant challenge in clinical settings.

Bile acids (BAs), classically regarded as detergents for dietary lipid absorption, have emerged as pivotal signaling molecules with systemic endocrine functions. The discovery of the Farnesoid X Receptor (FXR) and Takeda G protein-coupled receptor 5 (TGR5) as BAs-activated receptors unveiled their profound influences on glucose, lipid, and energy metabolism. BAs are first synthesized in hepatocytes and further metabolized by gut microbes, can either circulate in enterohepatic system or be found in circulations to exert various effects. More recently, the gut-brain axis has been identified as a critical pathway through which BAs exert significant effects on central nervous system (CNS) function and health. Based on research progresses mentioned above, this review systematically delineates the synthesis, metabolism, and classification of BAs, with a focus on the intricate crosstalk between the hepatic-gut BA axis and the brain. In addition, we explore the compelling evidences linking BAs dysregulation to a spectrum of neurological disorders, including neurodegenerative diseases (Alzheimer's and Parkinson's disease), depression, and hepatic encephalopathy. Besides, the potential mechanisms, such as alleviating neuroinflammation, maintaining the integrity of blood-brain barrier, increasing the neuronal survival, and modulating neurotransmitter systems are further elucidated. Finally, strategies of dietary intervention through phytochemicals to modulate the BAs pool for improved neurological outcomes are summarized and discussed. By integrating pre-clinical and clinical findings, this review aims to establish a foundation for understanding BAs as novel therapeutic targets in neurology and nutritional neuroscience.

Mercury (Hg) is a global environmental concern due to its microbial conversion to methylmercury (MeHg), a potent neurotoxin that bioaccumulates in food webs and poses risks to ecosystems and human health. Thiol functional groups (RSH) play an important role in controlling Hg(II) speciation and bio-uptake in methylating bacteria, yet the spatial distribution and density of these thiols within cells remain largely unknown. We isolated subcellular fractions of the Hg methylating bacterium Geobacter sulfurreducens in the exponential growth phase, and used Hg L _III -edge EXAFS (Extended X-ray Absorption Fine Structure) to quantify thiols in the extracellular medium, inner and outer membranes, periplasm and cytoplasm. The whole-cell thiol content was determined to be 1.3 × 10^-10 μmol cell^-1. The inner membrane contributed 7.1 × 10^-11 (53%), the outer membrane 1.2 × 10^-11 (9%), the periplasm 3.6 × 10^-11 (27%) and the cytoplasm 1.5 × 10^-11 μmol cell^-1 (11%). The extracellular fraction contributed an additional 5.7 × 10^-11 μmol cell^-1, corresponding to 30% of the thiols of the cell culture. Local thiol density (thiols normalized to TOC in individual compartment, RSH/TOC, μmol g^-1 C) was 36, 450, 140, 600 and 29 μmol g^-1 C in the cytoplasm, inner membrane, periplasm, outer membrane and extracellular fractions, respectively. EXAFS analyses demonstrate Hg-thiolate coordination across all compartments, with Hg-O/N bonding and elemental Hg⁰ formed at higher Hg loadings. In the periplasm, Hg-disulfide and traces of β-HgS were detected. The high thiol density at the membranes, relative to other compartments, may imply they have an important role in the retention and internalization of Hg(II). Periplasmic thiols may modulate Hg(II) transfer between membranes, and cytoplasmic thiols may regulate the intracellular availability of Hg(II) for methylation. This work provides the first compartment-resolved quantification of thiol abundances and densities in a model Hg-methylating bacterium at subcellular level, offering a mechanistic framework for understanding the speciation, bioavailability, and subcellular transformation of Hg(II) with relevance for other soft metals (e.g., Cd, Pb, Zn, Ag, and Cu).