Frontiers in Microbiology最新文献

Natural whey starter (NWS) cultures play a pivotal role in the production of Parmigiano Reggiano (PR) Protected Designation of Origin (PDO) cheese; however, their microbial ecology and functional dynamics remain only partially understood. In particular, Lactobacillus delbrueckii subsp. lactis, a dominant species in type-D NWS communities, exhibits impaired cultivability that limits its isolation and characterization. Consequently, most studies have focused on strain variability within Lactobacillus helveticus, which is predominant in type-H NWS communities. In this study, we evaluated the effects of 14 different medium supplementations on the recovery and maintenance of L. delbrueckii subsp. lactis isolates from two PR NWS samples representatives of type-D and type-H communities. Although most supplementations increased lactobacilli plate counts compared with the control MRS medium, they failed to sustain cell viability during the purification for culture collection establishment. Moreover, these media altered species ratios in favor of L. helveticus, even when L. delbrueckii dominated the community according to metagenomic profiling (type-D NWS). Supplementation of MRS medium with cysteine and formic acid enabled the recovery of viable L. delbrueckii subsp. lactis isolates, accounting for 35% of the strains obtained from type-D NWS. Cross-feeding experiments further revealed that co-culturing L. delbrueckii with the formate-producing Streptococcus thermophilus significantly enhanced milk acidification compared with monocultures, indicating a beneficial metabolic interaction. In contrast, no such improvement was observed in the presence of L. helveticus, likely due to negative interactions with L. delbrueckii subsp. lactis. Accordingly, the impaired cultivability of L. delbrueckii subsp. lactis could thus be partially alleviated either in co-culture with S. thermophilus or under axenic conditions mimicking natural metabolite exchange between these species.

Pseudomurein, a glycan polymer present in the cell wall, is found in the orders Methanobacteriales and Methanopyrales. It possesses glycan units and peptide chains similar to those of bacterial peptidoglycan (murein). However, the biosynthesis of pseudomurein remains unknown. In this study, we identified and characterized several key enzymes, such as PMurBCE ligases, that are proposed to catalyse peptide chain biosynthesis. Specifically, PMurB catalyses the conjugation of UDP-Glu and Pi, forming UDP. PMurC then transfers alanine or threonine to UDP-Glu, and PMurE adds lysine to the PMurC product. These reactions represent the enzymatic activities of PMurBCE ligases in methanogens. Structural model analyses indicated that archaeal PMur enzymes share an overall structural arrangement similar to that of bacterial Mur ligases but exhibit specificity for different substrates. The structural model data provide insights into pseudomurein synthesis in methanogens and create promising avenues for biotechnological applications in methanogens, such as gene editing and the development of novel antibacterial agents targeting methanogenic archaea.

Objective: To analyze the clinical phenotype and molecular characteristics of three Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) strains isolated from different sites of the same patient, providing an experimental basis for clinical anti-infection treatment and nosocomial infection prevention and control.

Methods: The collected strains were tested for antimicrobial susceptibility using an automatic drug sensitivity analyzer. Whole-genome sequencing was performed to analyze the presence of resistance and virulence genes and to determine the classification and homology of the three strains.

Results: The three K. pneumoniae strains were classified as ST11/K47/O13. Whole-genome sequencing revealed that all strains carried the KPC-type carbapenemase gene, and the high-virulence genes, rmpA2, iroB and iutA, along with three plasmids. Antimicrobial susceptibility testing showed that all strains were resistant to carbapenems, including imipenem and meropenem.

Conclusion: The three clinically isolated K. pneumoniae strains were highly virulent and carbapenem-resistant, all carrying the KPC resistance gene. They caused multi-site infections through hematogenous dissemination. These findings highlight the need for heightened clinical vigilance and strengthened monitoring, prevention, and control of drug-resistant infections.

Fusarium verticillioides is a major fungal pathogen of maize and a primary cause of contamination of kernels with fumonisins-mycotoxins that threaten food safety and animal health. This study examined the influence of genetic diversity of F. verticillioides on the development of a fumonisin risk index. To do this, the effect of temperature (10-40 °C) on growth as assessed by ergosterol levels and fumonisin production in the fungus was assessed by liquid chromatography-mass spectrometry analysis, and the resulting data were subjected to a battery of analyses, including least squares means, Baranyi and Ratkowsky analyses. Although there was considerable variation among strains, the general trend was that growth of F. verticillioides occurred over a broader range of temperatures (15-35 °C) than fumonisin production (optimal at 20-30 °C). Growth and production were positively correlated (R² = 0.524 overall; R² = 0.78 at 30 °C), although the strength of this relationship varied with temperature. Production of the four major B-series fumonisin analogs (FB₁-FB₄) varied among strains, but for all strains the ratio of FB₁-FB₂ tended to increase with increasing temperature. These results demonstrate that fumonisin risk is shaped by a complex interplay of strain genetics and environmental conditions. The strain-dependent differences in growth kinetics, toxin production, and analog composition underscore the need for risk indices that integrate both environmental and genetic parameters to improve predictive models for mycotoxin contamination and targeted strategies to limit contamination during maize production and storage.

Anaerobic degradation of aromatic hydrocarbons such as toluene plays a critical role in the natural and engineered attenuation of contaminated environments. Here, we developed and characterized a microbial consortium enriched under strictly anoxic conditions, capable of sustained toluene degradation through sulfate reduction. By integrating biodegradation kinetics, long-read 16S rRNA profiling, and genome-resolved metagenomics, we elucidated the structure and function of a multi-guild community. The consortium was co-dominated by Desulfoprunum, a sulfate-reducing bacterium (SRB), and Sulfurovum-affiliated sulfur oxidizers (~34% each), with additional members including Stenotrophomonas, Achromobacter, and Stutzerimonas. Such co-dominance appears uncommon, as sulfate-reducing enrichments are often characterized by low diversity and the predominance of a single lineage, such as Desulfobacula or Desulfosarcina in marine systems. Genome-resolved analyses recovered seven metagenome-assembled genomes (MAGs) with distinct but complementary metabolic roles. Desulfoprunum encoded the fumarate-addition pathway (bss/bbs) for anaerobic toluene activation and dissimilatory sulfate reduction (aprAB, dsrAB). In contrast, Sulfurovum and several Gammaproteobacteria encoded sulfide:quinone oxidoreductase (sqr), coupling H₂S detoxification to energy conservation, while a Moranbacterales MAG carried a putative sulfhydrogenase (hydAB) potentially catalyzing elemental sulfur (S°) reduction. Additional MAGs encoded assimilatory sulfate reduction (cys), suggesting integration of sulfur into biosynthetic pathways. Together, these features are consistent with the presence of a putative distributed sulfur redox loop, in which biogenic H₂S may be recycled via oxidation and reduction reactions mediated by co-occurring taxa. This sulfur loop is hypothesized to contribute to buffering sulfide toxicity and stabilize redox dynamics, thereby potentially supporting long-term toluene degradation under sulfidic conditions. Our findings highlight anaerobic degradation as a community-driven process enabled by sulfur-cycling interactions. By revealing the role of cryptic sulfur cycling in stabilizing hydrocarbon degradation, this work offers a new framework for designing bioremediation strategies in contaminated anoxic environments.

Introduction: Virus-Like Particles (VLPs) are viral protein structures widely used as adjuvants in vaccine formulations due to their ability to stimulate the innate immune response, thereby contributing to the activation of adaptive immunity through the production of different IgG subclasses. The present study evaluated the adjuvant potential of recombinant structural proteins of the Triatoma virus VLPs (TrV-VLPs: VP1, VP2, and VP3) in experimental immunisation protocols for American Cutaneous Leishmaniasis and Chagas disease.

Methods: BALB/c mice were immunised with native antigens of Leishmania amazonensis or chimeric recombinant antigens of Trypanosoma cruzi in association with different adjuvants, including aluminium hydroxide, incomplete Freund's adjuvant, and VPs structural proteins. The induction of specific antibodies (anti-L. amazonensis or anti-recombinant proteins of T. cruzi) was measured by ELISA to determine the IgG subclass profile.

Results and discussion: Immunisation with L. amazonensis antigens revealed that VPs preferentially induced IgG2b and IgG3 antibodies, whereas in experiments with T. cruzi antigens, IgG2b was predominant, accompanied by similar levels of IgG2a and IgG3, compared to lower IgG1 responses. These findings suggest that recombinant structural proteins of TrV-VLPs represent a promising adjuvant strategy capable of modulating humoral immune responses, offering potential applications in vaccine development against protozoan parasites such as Leishmania spp. and T. cruzi.

Background: Sepsis and septic shock are severe complications for surgical malignancy patients. Conventional diagnostics often fail to capture the complex infectome in these populations. This study aimed to characterize the distinct microbial and resistome landscapes in cancer versus non-cancer patients using multi-site metagenomic next-generation sequencing (mNGS) to support specific antimicrobial strategies.

Methods: We conducted a single-center retrospective cohort study at the General Surgery ICU of Xuanwu Hospital, including 107 septic shock patients (52 cancer; 55 non-cancer). mNGS was performed on blood, bile, ascitic fluid, and bronchoalveolar lavage samples to identify pathogens and antibiotic resistance genes (ARGs). Findings were analyzed for their association with ICU length of stay and mortality.

Results: Cancer patients were significantly older (median 68 vs. 51 years, p < 0.0001) with higher comorbidity scores (CCI: 7.0 vs. 4.0, p = 0.006). However, mNGS revealed a lower pathogen detection rate in cancer patients (53.85% vs. 85.45%, p = 0.0006) and a lower incidence of bacteremia (25.0% vs. 45.45%, p = 0.0426). Cancer patients had shorter ICU LOS (9 vs. 13 days, p = 0.0369) and antibiotic durations (7 vs. 11 days, p = 0.0368). Dominant pathogens included Klebsiella pneumoniae and Enterococcus faecium, harboring diverse ARGs across beta-lactam and aminoglycoside categories. Multivariate Cox regression identified IL-6 (p = 0.018) was significant prognostic indicators for cancer patients. We also examined the distribution of virulence factors, despite their low detection rates.

Conclusion: Septic shock in cancer patients exhibits a unique resistome signature and distinct prognostic drivers. The identification of microbial targets via mNGS was associated with the implementation of targeted antimicrobial strategies and inflammation monitoring. These findings suggest that mNGS provides valuable molecular insights that may support clinical management and prognostic stratification for cancer patients in the surgical ICU.

Introduction: The direct zoonotic risks associated with the growing online trade of live pets remain in adequately understood.

Methods: We investigate a human case of severe psittacotic pneumonia in Zhejiang Province, China, in which the patient's only avian exposure was through parrots recently purchased online. Using targeted probe-capture sequencing-a method designed for uncultivable, low-biomass pathogens-we recovered 13 high-quality Chlamydia psittaci genomes directly from the patient, the asymptomatic parrots, and their shared home environment.

Results: Comparative genomic analysis revealed >99.99% average nucleotide identity across all samples, providing definitive evidence of parrot-to-human transmission. The causative strain was identified as a novel sequence type (ST388) within the known virulent genotype A.

Conclusion: This investigation provides the first whole-genome confirmation of psittacosis transmission via online pet commerce. It establishes a practical genomic framework for investigating similar sporadic zoonoses and underscores the urgent need for targeted surveillance of this emerging and risk communication in this growing digital marketplace.