Fems Microbiology Letters最新文献

Bentonite is an important component of deep geological repositories for long-term storage of used nuclear fuel. Studying the microbiology of bentonite exposed to various conditions is relevant because certain microorganisms (e.g. those that produce corrosive sulfide or gaseous metabolites) could lead to deterioration of engineered barrier components of the repository. In previous research, a high degree of variability in the abundance of culturable microorganisms among replicate samples has been observed. The purpose of this study was to test whether experimental technique (e.g. inadequate mixing of bentonite) or extremely low biomass represent mechanisms to explain such variability. Using a combination of cultivation- and DNA-based techniques to study six replicate hydrated bentonite microcosms, as well as six replicate bentonite aliquots originating from the same hydrated bentonite microcosm, the results of this study demonstrate that observed heterogeneity is likely not due to inadequate bentonite mixing. Instead, the data indicate that low biomass of as-received bentonite leads to unique populations of culturable bacteria associating with each sample, or to a lesser degree within different areas of a single bentonite sample used to establish a microcosm. Because some microorganisms that grow in bentonite are culturable under commonly used cultivation conditions and others are not, this can lead to differences in culture-based abundance estimates among replicate samples. Although cultivation is a useful technique to demonstrate viability of microorganisms in bentonite, the results of this study highlight the importance of a multifaceted experimental approach (i.e. coupling cultivation to DNA-based analysis) and careful analysis of replicates when working with such low biomass samples.

Arcobacter butzleri, a foodborne pathogen of increasing public health relevance and associated with the gut of warm blooded animals is widely distributed in aquatic environments. Its association with the extensively studied faecal indicator, Escherichia coli remains unclear, yet is important for clarifying the ecology of pathogens and assessing risks. This study evaluated the prevalence and correlation between A. butzleri and E. coli in finfish, shellfish, and water sampled across multiple contamination points- markets, landing centres, and fishing vessels in Mumbai, India. A total of 70 samples (30 finfish, 30 shellfish, and 10 water) were tested using a miniaturized most probable number-quantitative polymerase chain reaction, which bypasses lengthy culture procedures and offers a reliable approach in the absence of a standard isolation method for A. butzleri. Arcobacter butzleri was present in 73% of the samples and E. coli in 81% samples indicating a high microbial burden of both organisms within this seafood ecosystem. Contamination varied by source, with market samples showing highest levels, followed by landing centres and lowest from on-board vessels, indicating post-harvest contamination influenced by nearshore water pollution. Regression analysis indicated positive correlation between A. butzleri and E. coli (ρ = 0.88, R² = 0.78, P < 0.001) and particularly robust associations were observed in shellfish and water matrices. This supports the close association of A. butzleri with sewage-impacted environments and its potential role as a supplementary indicator of fecal contamination.

Shiga toxin (Stx) is the primary virulence factor of Shiga toxin-producing Escherichia coli (STEC). Stx is categorized into Stx1 and Stx2 and further classified into several subtypes based on amino acid sequence variations. During routine surveillance of STEC isolates in Japan, we identified strain 2021H102 which harbored an uncommon stx subtype. Whole genome sequencing combined with matrix-assisted laser desorption/ionization-time of flight mass spectrometry analysis revealed that 2021H102 was a Stx2j-producing E. coli. Despite similarity among the sequences of Stx2j encoding prophages, phylogenetic analysis revealed that stx2j-positive E. coli genomes are diverse. 2021H102 clustered with genomes identified in the United States by core-genome single nucleotide variant-based phylogenetic analysis, implying that 2021H102 may have been an imported case. Several detection PCR primers failed to amplify stx2j, implying that stx2j-positive STEC might not be detected in some clinical laboratories. To our knowledge, this is the first report of Stx2j-producing E. coli isolated from outside of North American continent.

Neisseria meningitidis (Nm), a commensal that colonizes the nasopharynx of 4.5%-24% of healthy humans, can cause invasive meningococcal disease (IMD). We hypothesized that distinct genotypic and/or phenotypic signatures might be found in carriage vs. invasive isolates. Carriage isolates were cultured from nasopharyngeal swabs (n = 267) collected from healthy students (aged 13-21 years) during the 2013 and 2014 school years in the Netherlands. Invasive isolates (n = 214) were cultured from all reported disease cases in the Netherlands from 2012 to 2014. Whole core genome sequences were determined for all isolates and comparisons of selected genotypic markers and phylogenomic associations between carriage and disease isolates were analyzed. While 30% of carriage isolates could not be assigned a genogroup, all the invasive isolates were successfully genogrouped. Genogroup B (MenB) predominated, representing 27% of carriage and 75% of IMD isolates. Sequence type (ST) complex diversity was dominated by four STs (ST-41/44, ST-213, ST-32, and ST-269) in both carriage and disease isolates. FHbp subfamily A variants were prevalent (79%) in carriage, whereas subfamily B variants were more frequent (69.6%) in disease. Carriage and IMD-causing Nm strains display similar ST and phylogenomic profiles; however, an increased FHbp subfamily B prevalence and an enhanced level of FHbp surface expression were noted in MenB disease-causing isolates.

A 3 × 3 factorial design was used to systematically evaluate the impact of three widely used emulsification methods [ultrasonication (UT), high-shear homogenization (HSH), or vortex mixing (VM)] at three treatment times (30, 60, or 120 s) on the antimicrobial efficacy of sage (SEO) and garlic (GEO) essential oil emulsions. Independent of essential oil used, antimicrobial activity was significantly (P < 0.05) influenced by both emulsification method and treatment time, with Gram-negative bacteria showing greater resistance. From the tested methods, emulsions prepared by UT or HSH for at least 60 s exhibited significantly (P < 0.05) higher antimicrobial activity, which might be associated with their significantly (P < 0.05) smaller particle size and polydispersity index. Additionally, UT and HSH produced more stable SEO emulsions, while GEO required ≥60 s treatment for stability and VM led to rapid destabilization regardless of oil or time. This study highlights the importance of selecting an appropriate emulsification method for producing essential oil emulsions with enhanced antimicrobial activity, which is important not only for antimicrobial testing but also for the overall functional performance of the emulsion.

Pulmonary infection is one of the major health problems worldwide, with common pathogens including viruses, bacteria, and fungi. During pulmonary infection, exosomes secreted by different immune cells serve as important communication mediators between cells and have the ability to regulate the immune system. Exosomes regulate lung immune responses by carrying bioactive molecules, including miRNA, proteins, and lipids, initiating and inhibiting inflammatory responses, pathogen clearance, and immune tolerance. This paper discusses multiple roles of exosomes in regulating the function of lung-resident innate immune cells (epithelial cells, macrophages, and neutrophils) and their potential effects in infectious diseases of the lung. In addition, the existing research has described the prospects of exosomes in immunotherapy. This review aims to summarise their role in the diagnosis and treatment of pulmonary infection in order to clarify the role and mechanism of exosomes in pulmonary infectious diseases.

The halophilic archaeon Haloferax mediterranei is a promising candidate for polyhydroxyalkanoate (PHA) production, offering several advantages due to its extremophilic physiology. While its primary PHA synthase, a class III enzyme composed of PhaCHme and PhaEHme subunits, has been well characterized, the genome encodes three additional phaC paralogs (phaC1, phaC2, and phaC3), which were previously labeled as cryptic and remain poorly understood. In this study, we systematically investigated these paralogs by employing a targeted bioinformatics pipeline, revealing notable diversity in PHA synthases among Halobacteriales and underscoring the distinctiveness of H. mediterranei. We further analysed the native transcriptional expression profiles of all phaC paralogs under three physiologically relevant conditions: growth-limiting and growth-permissive conditions, as well as valeric acid supplementation to alter PHA monomer composition. Quantitative RT-PCR analysis demonstrated that all three paralogs are transcriptionally active and differentially expressed, refuting earlier assumptions of their cryptic nature. Expression patterns were found not to correlate to polymer composition but to be dependent on growth phase, suggesting a potential physiological role for each paralog in native PHA metabolism. These findings offer new insights into the functional complexity of PHA biosynthesis in H. mediterranei and lay the groundwork for future metabolic engineering aimed at optimizing biopolymer production.

Numerous Gram-negative bacteria possess N-acyl-L-homoserine lactone (AHL)-mediated quorum-sensing (QS) systems that regulate the activation of specific genes. Burkholderia plantarii causes rice seedling blight by producing the phytotoxin tropolone. In this study, we investigated multiple AHL-type QS systems in B. plantarii MAFF 301723T and their involvement in virulence regulation. MAFF 301723 harbors three AHL-mediated QS systems, designated plaI1/plaR1, plaI2/plaR2, and plaI3/plaR3. The plaI1/plaR1 system, which produces N-octanoyl-l-homoserine lactone, is functional and essential for swarming motility. When forced expression of plaI2 induces the biosynthesis of 3-OH-C10-HSL, it was suggested that expression is rarely observed in wild-type MAFF 301723. The plaI3 gene directs the synthesis of the putative C16:2-HSL, which is a rare AHL bearing two double bonds in the hexadecanoyl chain that has not been previously reported in Burkholderia spp. The plaI3/plaR3-QS system is crucial for tropolone production. These findings suggest that multiple QS systems collectively contribute to the complex virulence regulation of B. plantarii, thereby providing new insights into the development of QS-targeted biocontrol strategies for agriculture.

Ankylosing spondylitis (AS) is a chronic inflammatory disease with a global prevalence, primarily affecting the axial skeleton. While traditional therapies are often employed before surgical interventions, pharmacotherapy is typically reserved for cases of unstable AS condition. The gut microbiota has been implicated in numerous pathological conditions. However, its specific role in AS remains poorly understood. To address this knowledge gap, we applied Mendelian randomization (MR) to explore potential causal relationships between gut microbiota and AS. For this analysis, we utilized two large-scale genome-wide association study datasets: one comprising 18 340 individuals across 24 cohorts for human gut microbiota, and another consisting of 9069 AS cases and 1550 controls for AS susceptibility. Following heterogeneity testing, assessment of horizontal pleiotropy and application of multiple MR methods and 'leave-one-out' analysis, we identified 10 bacterial traits associated with AS risk. These include four risk-increasing factors: Actinobacteria (class), Streptococcaceae (family), Enterorhabdus (genus), and the Ruminococcaceae NK4A214 group (genus); and six risk-decreasing factors: Lactobacillaceae (family), Rikenellaceae (family), Anaerotruncus (genus), Eubacterium oxidoreducens group (genus), Howardella (genus), and Oscillibacter (genus). This study provides novel insights into the gut-spine axis and suggests potential avenues for AS management through microbiota-targeted interventions.