Journal of Microbiology最新文献

Bandavirus dabieense, a single-stranded RNA virus, is the causative agent of severe fever with thrombocytopenia syndrome (SFTS), a disease associated with high fatality rates. Early and accurate diagnosis is essential for improving clinical outcomes, particularly given the limited therapeutic options and high mortality rates associated with SFTS. However, while highly sensitive, conventional diagnostic methods such as PCR and qRT-PCR require specialized laboratory facilities and trained personnel, making them impractical for rapid detection in resource-limited settings. To address these challenges, we developed a rapid and highly sensitive assay for Bandavirus dabieense detection by integrating reverse transcription loop-mediated isothermal amplification (RT-LAMP) with CRISPR/Cas12a technology. LAMP primers and guide RNA sequences were designed to target the L gene, ensuring broad detection across viral genotypes. The optimized assay demonstrated a detection limit of 5 RNA copies per reaction, showing more sensitivity than qRT-PCR, and exhibited 100% concordance with qRT-PCR results in clinical samples. Given its speed, accuracy, and field applicability, this LAMP-CRISPR/Cas12a-based assay represents a promising diagnostic tool for early SFTSV detection, particularly in resource-constrained environments where conventional molecular diagnostics are not readily available.

Porins in the outer membrane (OM) of Gram-negative bacteria play two main functions: passage of various extracellular molecules and maintenance of membrane integrity. OmpC, a non-specific porin, is involved in both functions; however, the exact mechanism of maintenance of membrane integrity remains unknown. In this study, we found that inhibiting cardiolipin biosynthesis partially restored the growth defect of the ompC mutant under envelope stress. Among the three enzymes involved in cardiolipin biosynthesis, ClsABC, this effect is primarily associated with ClsA. Notably, the deletion of ClsA also suppressed the similar phenotypes of an Escherichia coli mutant lacking YhdP, a transmembrane protein involved in phospholipid transport from the inner membrane to the OM. Collectively, these results imply that OmpC may contribute to membrane integrity, partially through mechanisms linked to transport or biosynthesis of phospholipids such as cardiolipin.

Mycobacterium avium complex (MAC) organisms are widespread environmental pathogens associated with chronic pulmonary infections. Although M. avium is known to invade epithelial cells, the molecular mechanisms underlying this process remain incompletely understood. In this study, we identified a novel role for MAVRS09815 (formerly MAV2054), a family 2A encapsulin nanocompartment shell protein, in mediating bacterial adhesion, epithelial cell invasion, and in vivo virulence. We engineered a recombinant M. smegmatis strain expressing MAV2054 (Ms_2054) and an M. avium MAV2054 deletion mutant (Δ2054). Ms_2054 exhibited enhanced epithelial invasion, whereas Δ2054 showed reduced intracellular survival. Recombinant MAV2054 protein was bound directly to human epithelial cells in a dose-dependent manner. Pretreatment of host cells with cytochalasin D or vinblastine significantly inhibited bacterial internalization, indicating that MAV2054-mediated invasion is cytoskeleton-dependent. Confocal and scanning electron microscopy revealed MAV2054-dependent membrane rearrangements during infection. Pull-down assays demonstrated that MAV2054 activates Cdc42, a key regulator of actin polymerization, with reduced activation observed in Δ2054-infected cells. In a murine intratracheal infection model, the Δ2054 exhibited significantly reduced bacterial burdens and lung inflammation compared to the wild type. These findings demonstrate that MAV2054 enhances M. avium virulence by promoting epithelial cell invasion through Cdc42-dependent cytoskeletal remodeling. This study reveals a previously unrecognized role for an encapsulin-like protein in host-pathogen interactions and highlights its potential as a therapeutic target in MAC infections.

The Bacillus subtilis spore crust is an exceptionally robust proteinaceous layer that protects spores under extreme environmental conditions. Among its key components, CgeA, a glycosylation-associated protein, plays a critical role in modifying crust properties through its glycosylated moiety, enhancing spore dispersal in aqueous environments. In this study, we present the high-resolution cryo-electron microscopy structure of the core region of CgeA at 3.05 Å resolution, revealing a doughnut-like hexameric assembly. The N-terminal regions are disordered, whereas the C-terminal region forms the core of the hexamer. Although the loop containing Thr112 was not resolved in the density map, its location can be inferred from surrounding residues, suggesting that Thr112 is situated on the exposed surface of the hexamer. On the opposite face, a distinct electrostatic pattern is observed, featuring a negatively charged central pore and a positively charged outer surface. Modeling and biochemical studies with the putative glycosyltransferase CgeB provide insights into how the glycosyl group is transferred to Thr112. This study offers a molecular-level understanding of the assembly, glycosylation, and environmental adaptability of the B. subtilis spore crust, with valuable implications for controlling spore formation in industrial applications.

Atopic dermatitis (AD) is a widespread inflammatory skin condition that affects the population worldwide. Given the implication of microbiota in AD pathogenesis, we investigated whether human-derived Lactobacillus strains could modulate AD. In this study, we identified Lactobacillus crispatus KBL693 as a probiotic candidate for AD treatment. In vitro, KBL693 suppressed mast cell degranulation and IL-4 production by T cells, suggesting its ability to attenuate key type 2 immune responses. Consistent outcomes were observed in a murine AD model, where oral administration of KBL693 alleviated disease symptoms and reduced hallmark type 2 immune markers, including plasma IgE as well as IL-4, IL-5, and IL-13 levels in skin lesions. In addition to downregulating these AD-associated immune responses, KBL693 promoted regulatory T cell (Treg) expansion in mesenteric lymph nodes, indicating its potential to restore immune balance. Collectively, these findings highlight the therapeutic potential of KBL693 for AD through enhancement of Tregs and suppression of type 2 immune responses.

A Gram-stain-negative, aerobic, non-motile, rod-shaped, and orange-pigmented bacterium, designated CJ426T, was isolated from ginseng soil in Anseong, Korea. Strain CJ426T grew optimally on Reasoner's 2A agar at 30°C and pH 7.0 in the absence of NaCl. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain CJ426T belonged to the family Chitinophagaceae and had the highest sequence similarity with Niabella hibiscisoli KACC 18857T (98.7%). The 16S rRNA gene sequence similarities with other members of the genus Niabella ranged from 92.3% to 98.1%. Phylogenomic analyses and overall genomic relatedness indices, including average nucleotide identity, average amino acid identity, and the percentage of conserved proteins values, supported the classification of strain CJ426T as a representative of a novel genus within the family Chitinophagaceae. Furthermore, genome-based analyses suggested that five members of the genus Niabella, including N. aquatica, N. defluvii, N. ginsengisoli, N. hibiscisoli, and, N. yanshanensis, should be separated from other Niabella species and be assigned as a novel genus. The major isoprenoid quinone of strain CJ426T was menaquinone-7 (MK-7). The predominant polar lipids were phosphatidylethanolamine and six unidentified aminolipids. The major fatty acids were iso-C15:0, iso-C15:1 G, and iso-C17:0 3-OH. The genome of strain CJ426T was 6.3 Mbp in size, consisting of three contigs, with a G + C content of 41.9%. Based on a polyphasic taxonomic approach, strain CJ426T represents a novel genus and species within the family Chitinophagaceae, for which the name Paraniabella aurantiaca gen. nov., sp. nov. is proposed. The type strain is CJ426T (= KACC 23908T = JCM 37728T).

Nosocomial infections caused by Pseudomonas aeruginosa (P. aeruginosa) have become increasingly common, particularly among immunocompromised individuals, who experience high mortality rates and prolonged treatment durations due to the limited availability of effective therapies. In this study, we screened for anti-ExoS compounds targeting P. aeruginosa and identified pycnogenol (PYC) as a potent inhibitor of the type III secretion system (T3SS), a major virulence mechanism responsible for the translocation of effectors such as ExoS. Using ELISA, western blotting, and real-time PCR analyses in both P. aeruginosa and infected H292 cells, we found that PYC significantly reduced T3SS activity. Mechanistically, PYC suppressed the transcription of T3SS-related genes by downregulating exsA expression in P. aeruginosa. Furthermore, pretreatment with PYC attenuated the cytotoxic effects and reduced the expression of proinflammatory cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and interleukin-18 (IL-18), in P. aeruginosa-infected H292 cells. These effects were associated with the inhibition of NF-κB signaling and inflammasome activation. Taken together, our findings suggest that PYC may serve as a promising therapeutic candidate against P. aeruginosa infections by targeting T3SS-mediated virulence and modulating host inflammatory responses.

Streptococcus mutans is a Gram-positive pathogen that causes dental caries and subsequent pulpal infection leading to pulpitis. Although dendritic cells (DCs) are known to be involved in disease progression and immune responses during S. mutans infection, little is known about the component of S. mutans responsible for the DC responses. Although the mannose phosphotransferase system (Man-PTS) is the primary sugar transporter of S. mutans, it is also a potential virulence factor. Since Man-PTS subunit IID (ManIID) embedded on the bacterial membrane is indispensable for Man-PTS function, we investigated its role in the maturation and activation of DCs stimulated with a ManIID-deficient strain (Δpts) of S. mutans and recombinant ManIID (rManIID) protein. When mouse bone marrow-derived DCs were treated with heat-killed S. mutans wild-type (WT) or Δpts, bacterial adherence and internalization of Δpts were lower than those of WT. Moreover, the heat-killed S. mutans Δpts strain was inferior to the wild-type in inducing expression of phenotypic maturation markers, such as CD80, CD86, MHC-I, and MHC-II, and proinflammatory cytokine, IL-6. In line with the trends in marker expression, the endocytic capacity of DCs treated with the Δpts strain was comparable to that of untreated DCs whereas DCs treated with the WT strain dose-dependently lost their endocytic capacity. Furthermore, rManIID dose-dependently promoted both phenotypic maturation marker expression and IL-6 production by DCs. Collectively, these results demonstrate that ManIID plays a crucial role in the adhesion and internalization of S. mutans into DCs and is one of the major immune-stimulating agents responsible for maturation and activation of DCs during S. mutans infection.