BMC Microbiology最新文献

Background: Iron (Fe) contamination in groundwater is a gradual yet significant concern driven by industrial, urban, and agricultural activities, resulting in undesirable organoleptic effects in drinking water. Surface immobilization of bacterial strains onto biochar offers a promising strategy for enhancing adsorption-based remediation.

Purpose: This study investigates the adsorption behaviour of Fe(II) ions using a bacterial-biochar immobilized adsorbent derived from rice husk and Bacillus subtilis, isolated from iron-rich soil samples near handpumps located in Haridwar, Uttarakhand, India. The goal was to evaluate the impact on the adsorption capacity for Fe (II) through various sorption and kinetic models, along with material modified properties.

Methods: Rice husk biochar was immobilized with Bacillus subtilis and characterized using SEM, BET surface area analysis, and FTIR spectroscopy. Batch adsorption experiments were conducted across Fe(II) concentrations of 10-40 mg/L. Three Sorption kinetics were modeled for fitting the data and similarly three Isotherm behaviors were assessed, supported by regression analyses.

Results: The bacterial-biochar immobilized adsorbent achieved 79.3% Fe(II) removal, outperforming pristine biochar. BET surface areas of 67.76 and 91.84 m²/g correlated with enhanced adsorption. The FTIR revealed functional groups (alkene: C-H stretching, alcohol: O-H bending, conjugated alkenes: C = C stretching) and metal carbonate structures, provided an insight of active bio sorption sites. A decline in adsorption at higher concentrations, indicated optimal performance at 10-15 mg/L concentration of Fe (II) ions. Kinetic (pseudo-first-order and Weber-Morris intraparticle diffusion) and isotherm (Freundlich and Redlich-Peterson) models validated the presence of heterogeneous adsorption sites.

Conclusions: Surface immobilization of Bacillus subtilis onto rice husk biochar significantly enhances Fe(II) adsorption. These findings highlight the potential of bacterial-biochar immobilized adsorbent as a basis for valorization of the green biotechnology usage in groundwater remediation applications.

Background: Pseudomonas aeruginosa is a Gram-negative pathogen frequently responsible for nosocomial infections and a significant problem in intensive care units. P. aeruginosa, as an opportunistic pathogen, increases mortality risks for severely wounded and immunocompromised individuals. The inherent drug-resistance of P. aeruginosa now requires novel therapeutics with multiple mechanisms that will offer lasting potency in the post-antibiotic era. Synthetic antimicrobial peptides (AMPs) are ideal, as their multiple modes of action slow resistance development. In this study, we investigated the potential of novel proprietary AMP OB1111 to effectively treat P. aeruginosa under standard antimicrobial susceptibility testing (AST) and host-mimicking conditions, in planktonic and biofilm states, and at sublethal and lethal concentrations.

Results: The highly virulent PA14 and moderately virulent PAO1 reference strains were used in these studies. OB1111 effectively displayed inhibitory and bactericidal activity against both strains under AST conditions in planktonic and biofilm states. OB1111 demonstrated anti-virulence activity under host-mimicking conditions by reducing pyoverdine production and early biofilm attachment at sublethal concentrations. Under AST conditions, sublethal doses of OB1111 gradually reduced planktonic PA14 and PAO1 growth but showed less efficacy against biofilms. Additionally, PAO1 biofilms showed reduced susceptibility to OB1111 in comparison to PA14 biofilms at sublethal concentrations. Of significance, scanning electron microscopy revealed that OB1111 effectively deformed and disintegrated PA14 and PAO1 membranes in both the planktonic and biofilm states.

Conclusions: OB1111 successfully demonstrated the capacity to combat P. aeruginosa as an anti-planktonic, anti-biofilm, and anti-virulence agent. Future studies should further examine specific mechanisms of action against PA14 and PAO1, along with testing against clinical isolates in AST and host-mimicking conditions.

Background: Phoebe bournei, a rare and endangered plant species in China, exhibits low seedling survival rates and slow growth. Although Trichoderma longibrachiatum-based organic fertilizer is beneficial, it remains unclear whether it can reduce chemical fertilizer dependence while promoting P. bournei growth. Here, P. bournei seedlings were treated with a combination of T. longibrachiatum-based organic fertilizer and reduced chemical fertilizer (designated as the HF treatment). This study was employed to investigate the synergistic mechanisms underlying growth promotion.

Results: Plant physiology, pedology, and amplicon sequencing were used to evaluate the growth of P. bournei seedlings. The HF treatment optimally promoted P. bournei seedling growth, with a 39.8% increase in seedling height compared to the control. Specifically, the treatment elevated the levels of auxin (IAA), abscisic acid (ABA), and jasmonic acid (JA) by 43.6, 50.2, and 63.1%, respectively, compared to the control. This treatment also enhanced plant nitrogen and phosphorus utilization. An increase in the relative abundances of potentially beneficial fungi (e.g., Trichoderma and Trichocladium) and bacteria (e.g., Gemmatimonas and Streptomyces) was observed under the HF treatment, which also suppressed fungal pathogens such as Fusarium.

Conclusions: This study revealed the synergistic mechanism by which T. longibrachiatum-based organic fertilizer and chemical fertilizer co-promote P. bournei seedling growth. Our findings offer a practical strategy for sustainable forestry to enhance the productivity of this rare and endangered tree species.

In intensive ruminant production, high-energy diets are commonly used to enhance animal productivity, as dietary formulation significantly influences rumen fermentation and microbial communities. This study investigated the effects of varying dietary energy levels on the rumen microbial community structure, function, and metabolic profiles in Small-tailed Han (STH) sheep. Thirty 6-month-old sheep were randomly assigned to three groups: high-energy (HE), conventional-energy (CE), and low-energy (LE). All groups were fed iso-nitrogenous diets formulated to provide high-, conventional-, and low-energy levels of 10.8, 9.5, and 8.2 MJ/kg of digestible energy (DE), respectively. Rumen content was collected post-slaughter and analyzed via metagenomic sequencing to assess microbial composition and function, alongside non-targeted metabolomics to characterize the rumen fluid metabolome. Results revealed that Bacteroidota and Bacillota were the dominant phyla. High-energy feeding significantly reduced the relative abundance of Bacteroidota while increasing that of Bacillota, leading to a markedly higher Bacillota-to-Bacteroidota ratio. Functional analysis indicated significant enrichment of carbohydrate metabolism pathways in the HE group, whereas the LE group exhibited enrichment in fundamental cellular processes such as ABC transporters and ribosome, indicating a "survival mode". Metabolomic analysis demonstrated that dietary energy levels substantially reshaped the rumen metabolomic profile. Metabolites in the HE group were enriched in pathways including steroid hormone biosynthesis and the prolactin signaling pathway, while the LE group showed enrichment in histidine metabolism and the TCA cycle. Several aromatic amino acid metabolic pathways were commonly enriched across comparisons. These findings indicate that while the composition of the dominant phyla (Bacteroidota and Bacillota) was conserved across diets with different digestible energy levels, this dietary variation altered community diversity, structure, functional potential, and profoundly reshaped the rumen metabolic environment. This study provides scientific evidence regarding the impact of dietary energy on rumen fermentation and production performance in fattening sheep.

Background: Recent evidence suggests that the human stomach hosts a diverse microbiota beyond Helicobacter pylori, and that shifts in microbial composition may influence gastric health. In particular, oral-origin bacteria may dominate the gastric niche in the absence of H. pylori, yet their specific roles in different gastroduodenal disorders remain unclear. This study aimed to profile and compare the gastric microbiota composition in Turkish patients with non-ulcer dyspepsia (NUD) and peptic ulcer disease (PUD), in order to better understand microbial profiles potentially associated with gastroduodenal disease.

Methods: Ninety-eight patients underwent endoscopic evaluation and were divided into two groups according to the presence or absence of ulcers. Group 1 (n = 52) included individuals with NUD, while Group 2 (n = 46) comprised patients with PUD. Gastric biopsy samples from both groups were analyzed for the relative abundance of H. pylori using quantitative real-time PCR (qPCR), and next-generation sequencing was employed for a comprehensive analysis of the gastric microbiota.

Results: In total, H. pylori DNA was detected in 71.4% (70/98) of the samples, with a significantly higher prevalence in PUD patients (82.6%) compared to NUD patients (61.5%) (p = 0.02). Distinct microbial profiles were observed based on H. pylori status. In NUD patients, Alloprevotella showed significantly higher relative abundance in H. pylori-negative samples (p < 0.05). Among PUD patients, the absence of H. pylori was associated with increased levels of Porphyromonas and Neisseria compared to NUD patients without H. pylori (p < 0.05). These genera, typically associated with the oral cavity, appeared to expand opportunistically when H. pylori was absent.

Conclusions: The absence of H. pylori in gastric disorders was linked to a notable shift in microbiota composition, with increased representation of oral-origin bacteria such as Alloprevotella, Porphyromonas, and Neisseria. These findings, observed in a Turkish patient cohort, may reflect a potentially compensatory or opportunistic microbial shift in H. pylori-negative gastroduodenal disease. As exploratory findings, this study represents the first analysis from Türkiye comparing gastric microbiota profiles in NUD and PUD patients and provides novel regional insight into gastric microbial ecology.

Background: Listeria monocytogenes is a major foodborne pathogen responsible for severe infections, mainly affecting pregnant women, the elderly, and immunocompromised individuals. In Spain, listeriosis has been insufficiently studied using modern molecular techniques, and genomic data from clinical isolates remain scarce. Long‑term genomic surveillance based on whole genome sequencing (WGS) has not yet been systematically applied. WGS has proven to be a powerful method for outbreak detection and for revealing transmission dynamics that remain hidden to conventional epidemiology. This study aimed to characterise clinical L. monocytogenes isolates from Gipuzkoa, a region in northern Spain, collected over more than a decade, and to investigate their genetic diversity, phylogenetic relationships, and virulence traits.

Results: Between 2010 and 2022, a total of 131 laboratory‑confirmed human listeriosis cases were diagnosed in Gipuzkoa. Among them, 127 genomes were successfully sequenced and analysed by core genome multilocus sequence typing (cgMLST) and single nucleotide polymorphism (SNP) approaches. Genomic analysis revealed that 47 cases (36%) were part of nine distinct clusters, some extending across periods of up to nine years, while 84 cases appeared sporadic. Importantly, several outbreaks previously considered independent were shown to originate from genetically related strains, highlighting the persistence of specific clones. By comparing our dataset with publicly available international L. monocytogenes genomes, we identified putative foodborne sources for human infections and demonstrated cross‑border connections with lineages circulating in other countries. Additionally, antibiotic resistance determinants were detected infrequently, in line with the low resistance rates described for L. monocytogenes.

Conclusions: This study represents one of the most comprehensive WGS‑based studies of listeriosis to date in Spain. Our findings demonstrate that more than one third of apparently sporadic cases were in fact part of persistent or recurrent genomic clusters, underscoring the hidden transmission potential of this pathogen. WGS analysis revealed links between cases that would not have been detected through routine epidemiology, providing critical insights into outbreak dynamics and long‑term circulation of L. monocytogenes. This regional study highlights the importance of implementing genomic surveillance for listeriosis and integrating all parts of the infection chain - from clinical diagnosis to food production and public health - to better guide responses and strengthen prevention and control strategies.

Background: Over the past few decades, the Brucella genus has seen a significant increase in novel strains that deviate from classical Brucella spp. due to their atypical phenotypes. B. inopinata, an atypical Brucella species first isolated from a patient, was recently found in a White's tree frog, raising the question of whether amphibians are reservoirs for these emerging human pathogens. Unfortunately, monitoring atypical Brucella remains challenging because misidentification with Ochrobactrum spp. and Brucella melitensis is common when using routine microbiological tests.

Results: In our study, we describe a Brucella strain isolated from White's tree frogs (Litoria caerulea) that were initially examined for chytridiomycosis after they had developed dermal abnormalities. Classical microbiological and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analyses and a species-specific polymerase chain reaction confirmed that isolate CVUAS_1139.3 is an atypical Brucella strain. This non-fastidious, fast growing, flagellated, and motile bacterium is not susceptible to lysis by the Brucella phages used for typing. Further characterization using the differential metabolic phenotyping approach, revealed that Brucella sp. CVUAS_1139.3 could be differentiated from classical Brucella spp., as well as from Ochrobactrum anthropi and O. intermedium, based on its metabolic activity. The substrate utilization patterns may be suitable for a simple and cost-effective diagnostic assay. Phylogenetic analysis positioned Brucella sp. CVUAS_1139.3 distant from the classical Brucella spp. within the novel, non-core Brucella clade. Within this clade, Brucella sp. CVUAS_1139.3 shares a close phylogenetic relationship with B. inopinata strains and various African bullfrog isolates, and it is most closely related to a recently identified human isolate from Australia. Antimicrobial resistance testing revealed that it is susceptible to antibiotics widely applied in standard treatment regimens. In human THP-1 macrophage-like cells, the replication rate of the novel Brucella frog isolate was comparable to that of B. inopinata.

Conclusion: In summary, the amphibian-derived strain Brucella sp. CVUAS_1139.3 clusters phylogenetically with and is phenotypically alike to previously reported isolates from amphibian hosts and human brucellosis patients within the novel, non-core clade. Our report and other studies suggest that exotic frogs are potential reservoirs for human pathogenic Brucella spp., which might pose an underestimated zoonotic hazard for exposed individuals.

BACKGROUND : Candidozyma (candida) auris poses a global health threat with increasing incidence in China, yet the molecular epidemiology and virulence traits of this pathogen remain insufficiently characterized.

Methods: This study conducted a comprehensive analysis of 39 C. auris isolates from 37 patients in three hospitals in Guangzhou using whole genome sequencing (WGS), antifungal susceptibility testing, extracellular hydrolase detection, biofilm-forming capacity assessment, and a Galleria mellonella infection model. Single nucleotide polymorphism (SNP) analysis, phylogenetic analysis, and resistance gene analysis were performed based on the WGS data.

Results: Phylogenetic analysis identified two major clades: Clade I (74.4%) and Clade III (25.6%), with co-infection by both clades observed in one patient. All isolates showed resistance to fluconazole but were sensitive to echinocandins, while most of Clade I showed resistance to amphotericin B. All isolates carried ERG11 mutation (K143R or F126L) associated with fluconazole resistance, while no mutations related to echinocandin and amphotericin B resistance genes were detected. Clade I isolates exhibited potent secreted aspartyl protease activity (SAP), which correlated with elevated pathogenicity and mortality in Galleria mellonella infection models. Clade III exhibited enhanced biofilm-forming capacity, which may facilitate colonization of the skin and healthcare environments.

Conclusions: In this study, we identified two major clades of C. auris prevalent in the Guangzhou area and compared their epidemiological characteristics, drug resistance profiles, and virulence factors. These include mutations in drug-resistant genes, hydrolase activity, biofilm formation ability, and pathogenicity in the Galleria mellonella infection model. Understanding the biological characteristics of C. auris, as well as studying its drug resistance mechanisms and virulence, is crucial for advancing our knowledge in this field. Our study contributes to the expansion of the genetic database of C. auris and provides a scientific foundation for enhancing infection control strategies and antifungal stewardship in South China.