Microorganisms最新文献

Klebsiella pneumoniae (K. pneumoniae, KP) is a significant opportunistic pathogen responsible for both nosocomial and community-acquired infections. Bacterial adhesion is the critical initial step for host colonization and the establishment of disease. In this study, we utilized a mariner transposon mutagenesis system to construct a mutant library from the clinical KP strain KP20, identifying a mutant with significantly impaired epithelial cell adhesion due to an insertion in the uspF gene. Genetic knockout experiments confirmed that uspF deletion markedly reduced the adhesion to human airway epithelial cells (Calu-3) and downregulated the transcription of type III pili-encoding genes (mrkABDF). Furthermore, uspF deficiency compromised antioxidant stress and serum resistance and increased susceptibility to dendritic cell and macrophage phagocytosis. In vivo challenge experiments further demonstrated that uspF deletion significantly attenuated K. pneumoniae virulence in mice. These findings provide important insights into the molecular pathogenesis of K. pneumoniae and identify UspF as a potential target for therapeutic intervention.

Concerns about microplastic pollution have risen as numerous studies have reported detection of microplastics in foods, including seafood. One emerging concern is the ability of microplastics to vector pathogens that can adhere to biofilms on microplastic surfaces. Here, we investigated whether microplastics can facilitate zoonotic protozoan parasite contamination in shellfish. Oysters were selected for this study because they are commonly eaten raw and can harbor zoonotic protozoan pathogens. Acclimated live oysters were exposed in closed aquaria to Cryptosporidium, Giardia, and Toxoplasma (oo)cysts that had been incubated in seawater either as protozoa alone (P treatment) or with preconditioned polyester microfibers (P + M treatment). After overnight exposure, oysters were transferred to clean seawater flow-through aquaria for depuration. Over the experimental period, oysters exposed to both protozoa and microfibers had significantly higher numbers of protozoan pathogens than oysters exposed to protozoa alone. Our study provides experimental evidence that microplastics may facilitate protozoan pathogen contamination in shellfish. These results demonstrate how anthropogenic pollution may have unintended consequences on infectious disease transmission in coastal ecosystems, with potential risk to wildlife populations and human public health.

Aflatoxin B₁ (AFB₁) produced by Aspergillus flavus poses severe food safety risks. Competitive exclusion using atoxigenic A. flavus strains offers a promising biological control approach to managing agricultural contamination by reducing populations of toxigenic strains and aflatoxin levels. However, reliable identification of atoxigenic strains remains challenging, and the mechanisms underlying competitive interactions between toxigenic and atoxigenic strains require clarification for effective implementation. Therefore, this study systematically analysed A. flavus strains for aflatoxin gene clusters and AFB₁ production to address these critical gaps. Our analysis revealed that atoxigenic strains had intron losses and high-impact mutations in several genes, particularly aflL and aflLa, which affect aflatoxin biosynthesis. Key genes norA/aflE, verA/aflN, and omtA/aflP emerged as mutation hotspots, sometimes causing false-negative PCR results that complicate strain identification. Also, AFB₁ production was inversely related to spore concentration on MEA medium, with fewer spores resulting in higher toxin levels. Interaction tests demonstrated that toxigenic and atoxigenic strains exhibited morphological changes only when co-cultured without physical separation, suggesting that this was mediated by diffusible molecules. Furthermore, differences in the levels of linoleic acid reduction products distinguished toxigenic from atoxigenic strains. These findings thus illuminate the complex genetic and metabolic factors influencing aflatoxin production and fungal interactions.

Studying the mechanisms by which Gram-negative heterotrophic bacteria transition from active metabolism to dormancy is an important task, as it is directly related to the problem of bacterial antibiotic resistance and the spread of nosocomial infections. Using electron microscopy, microbiology, and molecular modeling, we investigated the dose-dependent mechanisms of action of 4-hexylresorcinol (4HR), a chemical analog of the anabiosis autoinducer, on the cell membranes of Gram-negative bacteria (using Escherichia coli as an example), leading to the formation of stressed, dormant, and mummified cells. It was shown that 4HR penetrates membranes equally easily both as single molecules and as micelles, distributing itself across the membrane so that the hydrocarbon radicals are aligned parallel to the lipid tails. When micelles penetrate the membrane, uneven distribution of 4HR within and between leaflets occurs, as well as lipid redistribution within the membrane, leading to the appearance of a third peak on the phospholipid electron density profile and a third black band in the membrane region in TEM images of such cells. At 4HR concentrations in solution of 200 µM, its micelles cover the cell membranes in a thick layer, penetrate into the membrane, and completely saturate it. Even higher concentrations create agglomerates or actually micellar arrays within the cell membranes, leading to cell death through mummification.

Stutzerimonas, a genus newly separated from the Pseudomonadaceae family in 2022, has attracted considerable attention due to its diverse metabolic capabilities and environmental adaptability. However, the mechanisms underlying its sulfur-oxidizing capacity and survival strategies in extreme environments remain poorly understood. Clarifying potential sulfur-oxidizing microbial groups contributes to a more accurate understanding of energy flow and elemental cycling in hydrothermal ecosystems. In this study, we isolated and identified a sulfur-oxidizing strain, designated 381-2^T, from sediments in the Tianxiu hydrothermal field of the northwest Indian Ocean, and proposed it as a new species of Stutzerimonas. Physiological characterizations demonstrated that strain 381-2^T could oxidize thiosulfate to tetrathionate and encoded the key sulfur oxidation gene tsdA. Cultivation with sulfide minerals showed that strain 381-2^T could influence sulfide mineral weathering through metabolic activities, such as pH regulation, and potentially promote the reprecipitation of metal ions on the microbial surface. Comparative genomic analysis of 322 Stutzerimonas genomes further revealed the widespread presence of the tsdA gene and metal resistance genes, suggesting potential adaptive strategies for survival in hydrothermal environments. This study expands the understanding of Stutzerimonas species and provides insights into their ecological roles in hydrothermal systems.

Leptospirosis is a major zoonosis, yet genetic data on Leptospira strains in animal reservoirs in Southern Vietnam are limited. This study aimed to detect and genotype pathogenic Leptospira in synanthropic small mammals. From 2016 to 2020, 856 animals were captured in three regions. Kidneys were screened by qPCR targeting pathogenic Leptospira 16S rRNA, and positive samples were genotyped via secY gene sequencing. The overall prevalence was 7.8%. Rattus norvegicus was the primary host (12.4% infected). Leptospira interrogans predominated (77.6%), followed by L. borgpetersenii (22.4%). Infection risk was significantly associated with the following factors: larger host body size (increased body mass and hindfoot length); capture in Ho Chi Minh City; and the rainy season. The study confirms the stable circulation of highly virulent L. interrogans in urban R. norvegicus populations. The identified risk factors provide a basis for targeted interventions to mitigate human health risks.

Advances in affordable genetic engineering have accelerated the creation and large-scale environmental release of genetically modified microorganisms (GMMs). While beneficial applications exist, GMMs may present unique, long-term risks to human and environmental health. Unlike static chemicals, GMMs are biologically active, self-replicating entities capable of rapid mutation and global dispersal. Current regulatory frameworks place responsibility on each country to regulate GMMs, without a clear, coordinated international policy. This review details critical risk scenarios, including horizontal gene transfer to native species and the possible disruption of vital human microbiomes (gut, oral, and infant), which could increase resistance to degradation, promote traits that expand a microbe's range of hosts or ecological niches, and enhance the production of novel metabolites with unexpected biological activity. In soil, GMMs may support the emergence of "super bugs" or destabilize carbon sequestration cycles, potentially impacting climate resilience. Engineered microbial enzymes in the food supply may also act as environmental drivers of autoimmunity. Given the limited understanding of microbial ecology, we propose a decision-based biosafety workflow emphasizing pre-release risk assessment and continuous post-release monitoring. We urge national and international regulators to adopt the precautionary principle to better protect human health and the environment from the potential negative outcomes of GMMs.

Cottonseed meal (CSM) is a cost-effective protein source, but its application is limited by the toxicity of free gossypol. Traditional physical and chemical detoxification methods are costly, energy-intensive, and cause nutrient loss, while microbial fermentation-based biological detoxification is considered more sustainable than chemical or physical approaches. This study reports an alkaline protease from the marine strain Bacillus safensis DL12 isolated from Yellow Sea sediments. Following cloning of its encoding gene and heterologous expression, enzymatic characterization of the purified enzyme revealed optimal activity at pH 8.0 and 50 °C, with Fe²⁺, Cu²⁺, Ni²⁺, and dithiothreitol (DTT) significantly enhancing its activity. Substrate hydrolysis analysis using the purified enzyme on soybean meal, peanut meal, rapeseed meal, and cottonseed meal demonstrated that, compared to the control group, cottonseed meal hydrolysates exhibited a 55.6% relative increase in peptide content and a 41.5% relative improvement in the degree of hydrolysis (DH), indicating higher hydrolysis efficiency among the four substrates. Notably, when hydrolyzing cottonseed meal with purified enzyme versus crude enzyme preparation at equivalent activity, the purified enzyme effectively reduced free gossypol content by 70% compared to the control, achieving more efficient detoxification than the crude enzyme preparation and most reported microbial treatments. These results highlight the potential of B. safensis DL12 protease as a marine-derived enzyme, offering promising prospects for enhancing protein digestibility and addressing the long-standing challenge of gossypol toxicity in cottonseed meal utilization.

The multiple-transferable resistance protein (MtrR) is a transcriptional repressor of the mtrCDE-encoded drug efflux pump and Type IV pilus biosynthesis (pilM), and an activator of penicillin-binding protein 1 (ponA) expression in Neisseria gonorrhoeae. Previously published microarray data suggested that MtrR is also an activator of ltgA expression in the gonococcus. LtgA is a lytic transglycosylase responsible for approximately half of recycled peptidoglycan fragments and released peptidoglycan-derived cytotoxins, which cause ciliary damage and induce specific inflammatory responses. The fragments generated by LtgA during peptidoglycan remodeling can either be recognized by the permease AmpG for uptake into the bacterial cytoplasm and recycled for new cell wall growth and general metabolism or released into the external milieu. Therefore, we sought to define the capacity of MtrR to regulate LtgA expression in gonococci. We show that MtrR binds to the ltgA promoter region in a concentration-dependent manner, and that this binding results both in increased ltgA mRNA transcription and LtgA protein levels during exponential growth. Deletion of mtrR in N. gonorrhoeae decreased peptidoglycan monomer release from growing cells and increased autolysis. These results suggest that MtrR regulation of ltgA impacts peptidoglycan-derived cytotoxin release and autolysis in the gonococcus. This study suggests a central role of MtrR in coordinating aspects of the cellular envelope that may contribute to gonococcal pathogenesis.

Porcine epidemic diarrhea virus (PEDV) is a major pathogen responsible for severe diarrhea, dehydration, and high mortality in neonatal piglets, continually threatening global swine production. Rapid differentiation of its major genotypes (classical G1, variant G2, and recombinant S-INDEL) is vital for molecular epidemiology and effective disease control, yet existing approaches rely mainly on time-consuming sequencing and phylogenetic analysis of the S gene. To overcome this limitation, we developed a novel triplex TaqMan-based real-time PCR assay for rapid detection and differentiation of the three PEDV genotypes. The assay demonstrated high sensitivity, with the lowest detection limit of 10² copies/μL, and strong specificity, showing no cross-reactivity with six other common swine pathogens (TGEV, PDCoV, PoRV, PRRSV, CSFV, and PRV). It also exhibited excellent reproducibility, with both intra- and inter-assay coefficients of variation maintained below 1.5%. In clinical validation, the assay showed 100% concordance with results obtained from S gene sequencing and phylogenetic analysis. Furthermore, testing of 160 clinical samples revealed cases of co-infection involving G2 and S-INDEL strains. In conclusion, this rapid, specific, and reproducible assay provides a reliable tool for routine molecular diagnosis, facilitating large-scale epidemiological surveillance and enabling genotype-informed control strategies against PEDV.